lock0lock.cc

/*****************************************************************************

Copyright (c) 1996, 2014, Oracle and/or its affiliates. All Rights Reserved.

This program is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free Software
Foundation; version 2 of the License.

This program is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with
this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA

*****************************************************************************/

/**************************************************//**
@file lock/lock0lock.cc
The transaction lock system

Created 5/7/1996 Heikki Tuuri
*******************************************************/

#define LOCK_MODULE_IMPLEMENTATION

#include "ha_prototypes.h"

#include "lock0lock.h"
#include "lock0priv.h"

#ifdef UNIV_NONINL
#include "lock0lock.ic"
#include "lock0priv.ic"
#endif

#include "dict0mem.h"
#include "usr0sess.h"
#include "trx0purge.h"
#include "trx0sys.h"
#include "srv0mon.h"
#include "ut0vec.h"
#include "btr0btr.h"
#include "dict0boot.h"
#include "ut0new.h"

#include <set>

/** Total number of cached record locks */
static const ulint	REC_LOCK_CACHE = 8;

/** Maximum record lock size in bytes */
static const ulint	REC_LOCK_SIZE = sizeof(ib_lock_t) + 256;

/** Total number of cached table locks */
static const ulint	TABLE_LOCK_CACHE = 8;

/** Size in bytes, of the table lock instance */
static const ulint	TABLE_LOCK_SIZE = sizeof(ib_lock_t);

/** Deadlock checker. */
class DeadlockChecker {
public:
	/** Checks if a joining lock request results in a deadlock. If
	a deadlock is found this function will resolve the deadlock
	by choosing a victim transaction and rolling it back. It
	will attempt to resolve all deadlocks. The returned transaction
	id will be the joining transaction id or 0 if some other
	transaction was chosen as a victim and rolled back or no
	deadlock found.

	@param lock lock the transaction is requesting
	@param trx transaction requesting the lock

	@return id of transaction chosen as victim or 0 */
	static const trx_t* check_and_resolve(
		const lock_t*	lock,
		const trx_t*	trx);

private:
	/** Do a shallow copy. Default destructor OK.
	@param trx the start transaction (start node)
	@param wait_lock lock that a transaction wants
	@param mark_start visited node counter */
	DeadlockChecker(
		const trx_t*	trx,
		const lock_t*	wait_lock,
		ib_uint64_t	mark_start)
		:
		m_cost(),
		m_start(trx),
		m_too_deep(),
		m_wait_lock(wait_lock),
		m_mark_start(mark_start),
		m_n_elems()
	{
	}

	/** Check if the search is too deep. */
	bool is_too_deep() const
	{
		return(m_n_elems > LOCK_MAX_DEPTH_IN_DEADLOCK_CHECK
		       || m_cost > LOCK_MAX_N_STEPS_IN_DEADLOCK_CHECK);
	}

	/** Save current state.
	@param lock lock to push on the stack.
	@param heap_no the heap number to push on the stack.
	@return false if stack is full. */
	bool push(const lock_t*	lock, ulint heap_no)
	{
		ut_ad((lock_get_type_low(lock) & LOCK_REC)
		      || (lock_get_type_low(lock) & LOCK_TABLE));

		ut_ad(((lock_get_type_low(lock) & LOCK_TABLE) != 0)
		      == (heap_no == ULINT_UNDEFINED));

		/* Ensure that the stack is bounded. */
		if (m_n_elems >= UT_ARR_SIZE(s_states)) {
			return(false);
		}

		state_t&	state = s_states[m_n_elems++];

		state.m_lock = lock;
		state.m_wait_lock = m_wait_lock;
		state.m_heap_no =heap_no;

		return(true);
	}

	/** Restore state.
	@param[out] lock current lock
	@param[out] heap_no current heap_no */
	void pop(const lock_t*& lock, ulint& heap_no)
	{
		ut_a(m_n_elems > 0);

		const state_t&	state = s_states[--m_n_elems];

		lock = state.m_lock;
		heap_no = state.m_heap_no;
		m_wait_lock = state.m_wait_lock;
	}

	/** Check whether the node has been visited.
	@param lock lock to check
	@return true if the node has been visited */
	bool is_visited(const lock_t* lock) const
	{
		return(lock->trx->lock.deadlock_mark > m_mark_start);
	}

	/** Get the next lock in the queue that is owned by a transaction
	whose sub-tree has not already been searched.
	Note: "next" here means PREV for table locks.
	@param lock Lock in queue
	@param heap_no heap_no if lock is a record lock else ULINT_UNDEFINED
	@return next lock or NULL if at end of queue */
	const lock_t* get_next_lock(const lock_t* lock, ulint heap_no) const;

	/** Get the first lock to search. The search starts from the current
	wait_lock. What we are really interested in is an edge from the
	current wait_lock's owning transaction to another transaction that has
	a lock ahead in the queue. We skip locks where the owning transaction's
	sub-tree has already been searched.

	Note: The record locks are traversed from the oldest lock to the
	latest. For table locks we go from latest to oldest.

	For record locks, we first position the iterator on first lock on
	the page and then reposition on the actual heap_no. This is required
	due to the way the record lock has is implemented.

	@param[out] heap_no if rec lock, else ULINT_UNDEFINED.

	@return first lock or NULL */
	const lock_t* get_first_lock(ulint* heap_no) const;

	/** Notify that a deadlock has been detected and print the conflicting
	transaction info.
	@param lock lock causing deadlock */
	void notify(const lock_t* lock) const;

	/** Select the victim transaction that should be rolledback.
	@return victim transaction */
	const trx_t* select_victim() const;

	/** Rollback transaction selected as the victim. */
	void trx_rollback();

	/** Looks iteratively for a deadlock. Note: the joining transaction
	may have been granted its lock by the deadlock checks.

	@return 0 if no deadlock else the victim transaction.*/
	const trx_t* search();

	/** Print transaction data to the deadlock file and possibly to stderr.
	@param trx transaction
	@param max_query_len max query length to print */
	static void print(const trx_t* trx, ulint max_query_len);

	/** rewind(3) the file used for storing the latest detected deadlock
	and print a heading message to stderr if printing of all deadlocks to
	stderr is enabled. */
	static void start_print();

	/** Print lock data to the deadlock file and possibly to stderr.
	@param lock record or table type lock */
	static void print(const lock_t* lock);

	/** Print a message to the deadlock file and possibly to stderr.
	@param msg message to print */
	static void print(const char* msg);

	/** Print info about transaction that was rolled back.
	@param trx transaction rolled back
	@param lock lock trx wants */
	static void rollback_print(const trx_t* trx, const lock_t* lock);

private:
	/** DFS state information, used during deadlock checking. */
	struct state_t {
		const lock_t*	m_lock;		/*!< Current lock */
		const lock_t*	m_wait_lock;	/*!< Waiting for lock */
		ulint		m_heap_no;	/*!< heap number if rec lock */
	};

	/** Used in deadlock tracking. Protected by lock_sys->mutex. */
	static ib_uint64_t	s_lock_mark_counter;

	/** Calculation steps thus far. It is the count of the nodes visited. */
	ulint			m_cost;

	/** Joining transaction that is requesting a lock in an
	incompatible mode */
	const trx_t*		m_start;

	/** TRUE if search was too deep and was aborted */
	bool			m_too_deep;

	/** Lock that trx wants */
	const lock_t*		m_wait_lock;

	/**  Value of lock_mark_count at the start of the deadlock check. */
	ib_uint64_t		m_mark_start;

	/** Number of states pushed onto the stack */
	size_t			m_n_elems;

	/** This is to avoid malloc/free calls. */
	static state_t		s_states[MAX_STACK_SIZE];
};

/** Counter to mark visited nodes during deadlock search. */
ib_uint64_t	DeadlockChecker::s_lock_mark_counter = 0;

/** The stack used for deadlock searches. */
DeadlockChecker::state_t	DeadlockChecker::s_states[MAX_STACK_SIZE];

#ifdef UNIV_DEBUG
/*********************************************************************//**
Validates the lock system.
@return TRUE if ok */
static
bool
lock_validate();
/*============*/

/*********************************************************************//**
Validates the record lock queues on a page.
@return TRUE if ok */
static
ibool
lock_rec_validate_page(
/*===================*/
	const buf_block_t*	block)	/*!< in: buffer block */
	__attribute__((warn_unused_result));
#endif /* UNIV_DEBUG */

/* The lock system */
lock_sys_t*	lock_sys	= NULL;

/** We store info on the latest deadlock error to this buffer. InnoDB
Monitor will then fetch it and print */
bool	lock_deadlock_found = false;

/** Only created if !srv_read_only_mode */
static FILE*		lock_latest_err_file;

/*********************************************************************//**
Reports that a transaction id is insensible, i.e., in the future. */
void
lock_report_trx_id_insanity(
/*========================*/
	trx_id_t	trx_id,		/*!< in: trx id */
	const rec_t*	rec,		/*!< in: user record */
	dict_index_t*	index,		/*!< in: index */
	const ulint*	offsets,	/*!< in: rec_get_offsets(rec, index) */
	trx_id_t	max_trx_id)	/*!< in: trx_sys_get_max_trx_id() */
{
	ib::error()
		<< "Transaction id " << trx_id
		<< " associated with record" << rec_offsets_print(rec, offsets)
		<< " in index " << index->name
		<< " of table " << index->table->name
		<< " is greater than the global counter " << max_trx_id
		<< "! The table is corrupted.";
}

/*********************************************************************//**
Checks that a transaction id is sensible, i.e., not in the future.
@return true if ok */
#ifdef UNIV_DEBUG

#else
static __attribute__((warn_unused_result))
#endif
bool
lock_check_trx_id_sanity(
/*=====================*/
	trx_id_t	trx_id,		/*!< in: trx id */
	const rec_t*	rec,		/*!< in: user record */
	dict_index_t*	index,		/*!< in: index */
	const ulint*	offsets)	/*!< in: rec_get_offsets(rec, index) */
{
	ut_ad(rec_offs_validate(rec, index, offsets));

	trx_id_t	max_trx_id = trx_sys_get_max_trx_id();
	bool		is_ok = trx_id < max_trx_id;

	if (!is_ok) {
		lock_report_trx_id_insanity(
			trx_id, rec, index, offsets, max_trx_id);
	}

	return(is_ok);
}

/*********************************************************************//**
Checks that a record is seen in a consistent read.
@return true if sees, or false if an earlier version of the record
should be retrieved */
bool
lock_clust_rec_cons_read_sees(
/*==========================*/
	const rec_t*	rec,	/*!< in: user record which should be read or
				passed over by a read cursor */
	dict_index_t*	index,	/*!< in: clustered index */
	const ulint*	offsets,/*!< in: rec_get_offsets(rec, index) */
	ReadView*	view)	/*!< in: consistent read view */
{
	ut_ad(dict_index_is_clust(index));
	ut_ad(page_rec_is_user_rec(rec));
	ut_ad(rec_offs_validate(rec, index, offsets));

	/* Temp-tables are not shared across connections and multiple
	transactions from different connections cannot simultaneously
	operate on same temp-table and so read of temp-table is
	always consistent read. */
	if (srv_read_only_mode || dict_table_is_temporary(index->table)) {
		ut_ad(view == 0 || dict_table_is_temporary(index->table));
		return(true);
	}

	/* NOTE that we call this function while holding the search
	system latch. */

	trx_id_t	trx_id = row_get_rec_trx_id(rec, index, offsets);

	return(view->changes_visible(trx_id));
}

/*********************************************************************//**
Checks that a non-clustered index record is seen in a consistent read.

NOTE that a non-clustered index page contains so little information on
its modifications that also in the case false, the present version of
rec may be the right, but we must check this from the clustered index
record.

@return true if certainly sees, or false if an earlier version of the
clustered index record might be needed */
bool
lock_sec_rec_cons_read_sees(
/*========================*/
	const rec_t*		rec,	/*!< in: user record which
					should be read or passed over
					by a read cursor */
	const dict_index_t*	index,	/*!< in: index */
	const ReadView*	view)	/*!< in: consistent read view */
{
	ut_ad(page_rec_is_user_rec(rec));

	/* NOTE that we might call this function while holding the search
	system latch. */

	if (recv_recovery_is_on()) {

		return(false);

	} else if (dict_table_is_temporary(index->table)) {

		/* Temp-tables are not shared across connections and multiple
		transactions from different connections cannot simultaneously
		operate on same temp-table and so read of temp-table is
		always consistent read. */

		return(true);
	}

	trx_id_t	max_trx_id = page_get_max_trx_id(page_align(rec));

	ut_ad(max_trx_id > 0);

	return(view->sees(max_trx_id));
}

/*********************************************************************//**
Creates the lock system at database start. */
void
lock_sys_create(
/*============*/
	ulint	n_cells)	/*!< in: number of slots in lock hash table */
{
	ulint	lock_sys_sz;

	lock_sys_sz = sizeof(*lock_sys) + OS_THREAD_MAX_N * sizeof(srv_slot_t);

	lock_sys = static_cast<lock_sys_t*>(ut_zalloc_nokey(lock_sys_sz));

	void*	ptr = &lock_sys[1];

	lock_sys->waiting_threads = static_cast<srv_slot_t*>(ptr);

	lock_sys->last_slot = lock_sys->waiting_threads;

	mutex_create("lock_sys", &lock_sys->mutex);

	mutex_create("lock_sys_wait", &lock_sys->wait_mutex);

	lock_sys->timeout_event = os_event_create(0);

	lock_sys->rec_hash = hash_create(n_cells);
	lock_sys->prdt_hash = hash_create(n_cells);
	lock_sys->prdt_page_hash = hash_create(n_cells);

	if (!srv_read_only_mode) {
		lock_latest_err_file = os_file_create_tmpfile();
		ut_a(lock_latest_err_file);
	}
}

/** Calculates the fold value of a lock: used in migrating the hash table.
@param[in]	lock	record lock object
@return	folded value */
static
ulint
lock_rec_lock_fold(
	const lock_t*	lock)
{
	return(lock_rec_fold(lock->un_member.rec_lock.space,
			     lock->un_member.rec_lock.page_no));
}

/** Resize the lock hash tables.
@param[in]	n_cells	number of slots in lock hash table */
void
lock_sys_resize(
	ulint	n_cells)
{
	hash_table_t*	old_hash;

	lock_mutex_enter();

	old_hash = lock_sys->rec_hash;
	lock_sys->rec_hash = hash_create(n_cells);
	HASH_MIGRATE(old_hash, lock_sys->rec_hash, lock_t, hash,
		     lock_rec_lock_fold);
	hash_table_free(old_hash);

	old_hash = lock_sys->prdt_hash;
	lock_sys->prdt_hash = hash_create(n_cells);
	HASH_MIGRATE(old_hash, lock_sys->prdt_hash, lock_t, hash,
		     lock_rec_lock_fold);
	hash_table_free(old_hash);

	old_hash = lock_sys->prdt_page_hash;
	lock_sys->prdt_page_hash = hash_create(n_cells);
	HASH_MIGRATE(old_hash, lock_sys->prdt_page_hash, lock_t, hash,
		     lock_rec_lock_fold);
	hash_table_free(old_hash);

	/* need to update block->lock_hash_val */
	for (ulint i = 0; i < srv_buf_pool_instances; ++i) {
		buf_pool_t*	buf_pool = buf_pool_from_array(i);

		buf_pool_mutex_enter(buf_pool);
		buf_page_t*	bpage;
		bpage = UT_LIST_GET_FIRST(buf_pool->LRU);

		while (bpage != NULL) {
			if (buf_page_get_state(bpage)
			    == BUF_BLOCK_FILE_PAGE) {
				buf_block_t*	block;
				block = reinterpret_cast<buf_block_t*>(
					bpage);

				block->lock_hash_val
					= lock_rec_hash(
						bpage->id.space(),
						bpage->id.page_no());
			}
			bpage = UT_LIST_GET_NEXT(LRU, bpage);
		}
		buf_pool_mutex_exit(buf_pool);
	}

	lock_mutex_exit();
}

/*********************************************************************//**
Closes the lock system at database shutdown. */
void
lock_sys_close(void)
/*================*/
{
	if (lock_latest_err_file != NULL) {
		fclose(lock_latest_err_file);
		lock_latest_err_file = NULL;
	}

	hash_table_free(lock_sys->rec_hash);
	hash_table_free(lock_sys->prdt_hash);
	hash_table_free(lock_sys->prdt_page_hash);

	os_event_destroy(lock_sys->timeout_event);

	mutex_destroy(&lock_sys->mutex);
	mutex_destroy(&lock_sys->wait_mutex);

	srv_slot_t*	slot = lock_sys->waiting_threads;

	for (ulint i = 0; i < OS_THREAD_MAX_N; i++, ++slot) {
		if (slot->event != NULL) {
			os_event_destroy(slot->event);
		}
	}

	ut_free(lock_sys);

	lock_sys = NULL;
}

/*********************************************************************//**
Gets the size of a lock struct.
@return size in bytes */
ulint
lock_get_size(void)
/*===============*/
{
	return((ulint) sizeof(lock_t));
}

/*********************************************************************//**
Gets the source table of an ALTER TABLE transaction.  The table must be
covered by an IX or IS table lock.
@return the source table of transaction, if it is covered by an IX or
IS table lock; dest if there is no source table, and NULL if the
transaction is locking more than two tables or an inconsistency is
found */
dict_table_t*
lock_get_src_table(
/*===============*/
	trx_t*		trx,	/*!< in: transaction */
	dict_table_t*	dest,	/*!< in: destination of ALTER TABLE */
	lock_mode*	mode)	/*!< out: lock mode of the source table */
{
	dict_table_t*	src;
	lock_t*		lock;

	ut_ad(!lock_mutex_own());

	src = NULL;
	*mode = LOCK_NONE;

	/* The trx mutex protects the trx_locks for our purposes.
	Other transactions could want to convert one of our implicit
	record locks to an explicit one. For that, they would need our
	trx mutex. Waiting locks can be removed while only holding
	lock_sys->mutex, but this is a running transaction and cannot
	thus be holding any waiting locks. */
	trx_mutex_enter(trx);

	for (lock = UT_LIST_GET_FIRST(trx->lock.trx_locks);
	     lock != NULL;
	     lock = UT_LIST_GET_NEXT(trx_locks, lock)) {
		lock_table_t*	tab_lock;
		lock_mode	lock_mode;
		if (!(lock_get_type_low(lock) & LOCK_TABLE)) {
			/* We are only interested in table locks. */
			continue;
		}
		tab_lock = &lock->un_member.tab_lock;
		if (dest == tab_lock->table) {
			/* We are not interested in the destination table. */
			continue;
		} else if (!src) {
			/* This presumably is the source table. */
			src = tab_lock->table;
			if (UT_LIST_GET_LEN(src->locks) != 1
			    || UT_LIST_GET_FIRST(src->locks) != lock) {
				/* We only support the case when
				there is only one lock on this table. */
				src = NULL;
				goto func_exit;
			}
		} else if (src != tab_lock->table) {
			/* The transaction is locking more than
			two tables (src and dest): abort */
			src = NULL;
			goto func_exit;
		}

		/* Check that the source table is locked by
		LOCK_IX or LOCK_IS. */
		lock_mode = lock_get_mode(lock);
		if (lock_mode == LOCK_IX || lock_mode == LOCK_IS) {
			if (*mode != LOCK_NONE && *mode != lock_mode) {
				/* There are multiple locks on src. */
				src = NULL;
				goto func_exit;
			}
			*mode = lock_mode;
		}
	}

	if (!src) {
		/* No source table lock found: flag the situation to caller */
		src = dest;
	}

func_exit:
	trx_mutex_exit(trx);
	return(src);
}

/*********************************************************************//**
Determine if the given table is exclusively "owned" by the given
transaction, i.e., transaction holds LOCK_IX and possibly LOCK_AUTO_INC
on the table.
@return TRUE if table is only locked by trx, with LOCK_IX, and
possibly LOCK_AUTO_INC */
ibool
lock_is_table_exclusive(
/*====================*/
	const dict_table_t*	table,	/*!< in: table */
	const trx_t*		trx)	/*!< in: transaction */
{
	const lock_t*	lock;
	ibool		ok	= FALSE;

	ut_ad(table);
	ut_ad(trx);

	lock_mutex_enter();

	for (lock = UT_LIST_GET_FIRST(table->locks);
	     lock != NULL;
	     lock = UT_LIST_GET_NEXT(locks, &lock->un_member.tab_lock)) {
		if (lock->trx != trx) {
			/* A lock on the table is held
			by some other transaction. */
			goto not_ok;
		}

		if (!(lock_get_type_low(lock) & LOCK_TABLE)) {
			/* We are interested in table locks only. */
			continue;
		}

		switch (lock_get_mode(lock)) {
		case LOCK_IX:
			ok = TRUE;
			break;
		case LOCK_AUTO_INC:
			/* It is allowed for trx to hold an
			auto_increment lock. */
			break;
		default:
not_ok:
			/* Other table locks than LOCK_IX are not allowed. */
			ok = FALSE;
			goto func_exit;
		}
	}

func_exit:
	lock_mutex_exit();

	return(ok);
}

/*********************************************************************//**
Sets the wait flag of a lock and the back pointer in trx to lock. */
UNIV_INLINE
void
lock_set_lock_and_trx_wait(
/*=======================*/
	lock_t*	lock,	/*!< in: lock */
	trx_t*	trx)	/*!< in/out: trx */
{
	ut_ad(lock);
	ut_ad(lock->trx == trx);
	ut_ad(trx->lock.wait_lock == NULL);
	ut_ad(lock_mutex_own());
	ut_ad(trx_mutex_own(trx));

	trx->lock.wait_lock = lock;
	lock->type_mode |= LOCK_WAIT;
}

/**********************************************************************//**
The back pointer to a waiting lock request in the transaction is set to NULL
and the wait bit in lock type_mode is reset. */
UNIV_INLINE
void
lock_reset_lock_and_trx_wait(
/*=========================*/
	lock_t*	lock)	/*!< in/out: record lock */
{
	ut_ad(lock->trx->lock.wait_lock == lock);
	ut_ad(lock_get_wait(lock));
	ut_ad(lock_mutex_own());

	lock->trx->lock.wait_lock = NULL;
	lock->type_mode &= ~LOCK_WAIT;
}

/*********************************************************************//**
Gets the gap flag of a record lock.
@return LOCK_GAP or 0 */
UNIV_INLINE
ulint
lock_rec_get_gap(
/*=============*/
	const lock_t*	lock)	/*!< in: record lock */
{
	ut_ad(lock);
	ut_ad(lock_get_type_low(lock) == LOCK_REC);

	return(lock->type_mode & LOCK_GAP);
}

/*********************************************************************//**
Gets the LOCK_REC_NOT_GAP flag of a record lock.
@return LOCK_REC_NOT_GAP or 0 */
UNIV_INLINE
ulint
lock_rec_get_rec_not_gap(
/*=====================*/
	const lock_t*	lock)	/*!< in: record lock */
{
	ut_ad(lock);
	ut_ad(lock_get_type_low(lock) == LOCK_REC);

	return(lock->type_mode & LOCK_REC_NOT_GAP);
}

/*********************************************************************//**
Gets the waiting insert flag of a record lock.
@return LOCK_INSERT_INTENTION or 0 */
UNIV_INLINE
ulint
lock_rec_get_insert_intention(
/*==========================*/
	const lock_t*	lock)	/*!< in: record lock */
{
	ut_ad(lock);
	ut_ad(lock_get_type_low(lock) == LOCK_REC);

	return(lock->type_mode & LOCK_INSERT_INTENTION);
}

/*********************************************************************//**
Checks if a lock request for a new lock has to wait for request lock2.
@return TRUE if new lock has to wait for lock2 to be removed */
UNIV_INLINE
ibool
lock_rec_has_to_wait(
/*=================*/
	const trx_t*	trx,	/*!< in: trx of new lock */
	ulint		type_mode,/*!< in: precise mode of the new lock
				to set: LOCK_S or LOCK_X, possibly
				ORed to LOCK_GAP or LOCK_REC_NOT_GAP,
				LOCK_INSERT_INTENTION */
	const lock_t*	lock2,	/*!< in: another record lock; NOTE that
				it is assumed that this has a lock bit
				set on the same record as in the new
				lock we are setting */
	bool		lock_is_on_supremum)
				/*!< in: TRUE if we are setting the
				lock on the 'supremum' record of an
				index page: we know then that the lock
				request is really for a 'gap' type lock */
{
	ut_ad(trx && lock2);
	ut_ad(lock_get_type_low(lock2) == LOCK_REC);

	if (trx != lock2->trx
	    && !lock_mode_compatible(static_cast<lock_mode>(
			             LOCK_MODE_MASK & type_mode),
				     lock_get_mode(lock2))) {

		/* We have somewhat complex rules when gap type record locks
		cause waits */

		if ((lock_is_on_supremum || (type_mode & LOCK_GAP))
		    && !(type_mode & LOCK_INSERT_INTENTION)) {

			/* Gap type locks without LOCK_INSERT_INTENTION flag
			do not need to wait for anything. This is because
			different users can have conflicting lock types
			on gaps. */

			return(FALSE);
		}

		if (!(type_mode & LOCK_INSERT_INTENTION)
		    && lock_rec_get_gap(lock2)) {

			/* Record lock (LOCK_ORDINARY or LOCK_REC_NOT_GAP
			does not need to wait for a gap type lock */

			return(FALSE);
		}

		if ((type_mode & LOCK_GAP)
		    && lock_rec_get_rec_not_gap(lock2)) {

			/* Lock on gap does not need to wait for
			a LOCK_REC_NOT_GAP type lock */

			return(FALSE);
		}

		if (lock_rec_get_insert_intention(lock2)) {

			/* No lock request needs to wait for an insert
			intention lock to be removed. This is ok since our
			rules allow conflicting locks on gaps. This eliminates
			a spurious deadlock caused by a next-key lock waiting
			for an insert intention lock; when the insert
			intention lock was granted, the insert deadlocked on
			the waiting next-key lock.

			Also, insert intention locks do not disturb each
			other. */

			return(FALSE);
		}

		return(TRUE);
	}

	return(FALSE);
}

/*********************************************************************//**
Checks if a lock request lock1 has to wait for request lock2.
@return TRUE if lock1 has to wait for lock2 to be removed */
ibool
lock_has_to_wait(
/*=============*/
	const lock_t*	lock1,	/*!< in: waiting lock */
	const lock_t*	lock2)	/*!< in: another lock; NOTE that it is
				assumed that this has a lock bit set
				on the same record as in lock1 if the
				locks are record locks */
{
	ut_ad(lock1 && lock2);

	if (lock1->trx != lock2->trx
	    && !lock_mode_compatible(lock_get_mode(lock1),
				     lock_get_mode(lock2))) {
		if (lock_get_type_low(lock1) == LOCK_REC) {
			ut_ad(lock_get_type_low(lock2) == LOCK_REC);

			/* If this lock request is for a supremum record
			then the second bit on the lock bitmap is set */

			if (lock1->type_mode
			    & (LOCK_PREDICATE | LOCK_PRDT_PAGE)) {
				return(lock_prdt_has_to_wait(
					lock1->trx, lock1->type_mode,
					lock_get_prdt_from_lock(lock1),
					lock2));
			} else {
				return(lock_rec_has_to_wait(
					lock1->trx, lock1->type_mode, lock2,
					lock_rec_get_nth_bit(lock1, true)));
			}
		}

		return(TRUE);
	}

	return(FALSE);
}

/*============== RECORD LOCK BASIC FUNCTIONS ============================*/

/**********************************************************************//**
Looks for a set bit in a record lock bitmap. Returns ULINT_UNDEFINED,
if none found.
@return bit index == heap number of the record, or ULINT_UNDEFINED if
none found */
ulint
lock_rec_find_set_bit(
/*==================*/
	const lock_t*	lock)	/*!< in: record lock with at least one bit set */
{
	for (ulint i = 0; i < lock_rec_get_n_bits(lock); ++i) {

		if (lock_rec_get_nth_bit(lock, i)) {

			return(i);
		}
	}

	return(ULINT_UNDEFINED);
}

/** Reset the nth bit of a record lock.
@param[in,out] lock record lock
@param[in] i index of the bit that will be reset
@return previous value of the bit */
UNIV_INLINE
byte
lock_rec_reset_nth_bit(
	lock_t*	lock,
	ulint	i)
{
	ut_ad(lock_get_type_low(lock) == LOCK_REC);
	ut_ad(i < lock->un_member.rec_lock.n_bits);

	byte*	b = reinterpret_cast<byte*>(&lock[1]) + (i >> 3);
	byte	mask = 1 << (i & 7);
	byte	bit = *b & mask;
	*b &= ~mask;

	if (bit != 0) {
		ut_ad(lock->trx->lock.n_rec_locks > 0);
		--lock->trx->lock.n_rec_locks;
	}

	return(bit);
}

/** Reset the nth bit of a record lock.
@param[in,out]	lock record lock
@param[in] i	index of the bit that will be reset
@param[in] type	whether the lock is in wait mode */
void
lock_rec_trx_wait(
	lock_t*	lock,
	ulint	i,
	ulint	type)
{
	lock_rec_reset_nth_bit(lock, i);

	if (type & LOCK_WAIT) {
		lock_reset_lock_and_trx_wait(lock);
	}
}

/*********************************************************************//**
Determines if there are explicit record locks on a page.
@return an explicit record lock on the page, or NULL if there are none */
lock_t*
lock_rec_expl_exist_on_page(
/*========================*/
	ulint	space,	/*!< in: space id */
	ulint	page_no)/*!< in: page number */
{
	lock_t*	lock;

	lock_mutex_enter();
	/* Only used in ibuf pages, so rec_hash is good enough */
	lock = lock_rec_get_first_on_page_addr(lock_sys->rec_hash,
					       space, page_no);
	lock_mutex_exit();

	return(lock);
}

/*********************************************************************//**
Resets the record lock bitmap to zero. NOTE: does not touch the wait_lock
pointer in the transaction! This function is used in lock object creation
and resetting. */
static
void
lock_rec_bitmap_reset(
/*==================*/
	lock_t*	lock)	/*!< in: record lock */
{
	ulint	n_bytes;

	ut_ad(lock_get_type_low(lock) == LOCK_REC);

	/* Reset to zero the bitmap which resides immediately after the lock
	struct */

	n_bytes = lock_rec_get_n_bits(lock) / 8;

	ut_ad((lock_rec_get_n_bits(lock) % 8) == 0);

	memset(&lock[1], 0, n_bytes);
}

/*********************************************************************//**
Copies a record lock to heap.
@return copy of lock */
static
lock_t*
lock_rec_copy(
/*==========*/
	const lock_t*	lock,	/*!< in: record lock */
	mem_heap_t*	heap)	/*!< in: memory heap */
{
	ulint	size;

	ut_ad(lock_get_type_low(lock) == LOCK_REC);

	size = sizeof(lock_t) + lock_rec_get_n_bits(lock) / 8;

	return(static_cast<lock_t*>(mem_heap_dup(heap, lock, size)));
}

/*********************************************************************//**
Gets the previous record lock set on a record.
@return previous lock on the same record, NULL if none exists */
const lock_t*
lock_rec_get_prev(
/*==============*/
	const lock_t*	in_lock,/*!< in: record lock */
	ulint		heap_no)/*!< in: heap number of the record */
{
	lock_t*		lock;
	ulint		space;
	ulint		page_no;
	lock_t*		found_lock	= NULL;
	hash_table_t*	hash;

	ut_ad(lock_mutex_own());
	ut_ad(lock_get_type_low(in_lock) == LOCK_REC);

	space = in_lock->un_member.rec_lock.space;
	page_no = in_lock->un_member.rec_lock.page_no;

	hash = lock_hash_get(in_lock->type_mode);

	for (lock = lock_rec_get_first_on_page_addr(hash, space, page_no);
	     /* No op */;
	     lock = lock_rec_get_next_on_page(lock)) {

		ut_ad(lock);

		if (lock == in_lock) {

			return(found_lock);
		}

		if (lock_rec_get_nth_bit(lock, heap_no)) {

			found_lock = lock;
		}
	}
}

/*============= FUNCTIONS FOR ANALYZING RECORD LOCK QUEUE ================*/

/*********************************************************************//**
Checks if a transaction has a GRANTED explicit lock on rec stronger or equal
to precise_mode.
@return lock or NULL */
UNIV_INLINE
lock_t*
lock_rec_has_expl(
/*==============*/
	ulint			precise_mode,/*!< in: LOCK_S or LOCK_X
					possibly ORed to LOCK_GAP or
					LOCK_REC_NOT_GAP, for a
					supremum record we regard this
					always a gap type request */
	const buf_block_t*	block,	/*!< in: buffer block containing
					the record */
	ulint			heap_no,/*!< in: heap number of the record */
	const trx_t*		trx)	/*!< in: transaction */
{
	lock_t*	lock;

	ut_ad(lock_mutex_own());
	ut_ad((precise_mode & LOCK_MODE_MASK) == LOCK_S
	      || (precise_mode & LOCK_MODE_MASK) == LOCK_X);
	ut_ad(!(precise_mode & LOCK_INSERT_INTENTION));

	for (lock = lock_rec_get_first(lock_sys->rec_hash, block, heap_no);
	     lock != NULL;
	     lock = lock_rec_get_next(heap_no, lock)) {

		if (lock->trx == trx
		    && !lock_rec_get_insert_intention(lock)
		    && lock_mode_stronger_or_eq(
			    lock_get_mode(lock),
			    static_cast<lock_mode>(
				    precise_mode & LOCK_MODE_MASK))
		    && !lock_get_wait(lock)
		    && (!lock_rec_get_rec_not_gap(lock)
			|| (precise_mode & LOCK_REC_NOT_GAP)
			|| heap_no == PAGE_HEAP_NO_SUPREMUM)
		    && (!lock_rec_get_gap(lock)
			|| (precise_mode & LOCK_GAP)
			|| heap_no == PAGE_HEAP_NO_SUPREMUM)) {

			return(lock);
		}
	}

	return(NULL);
}

#ifdef UNIV_DEBUG
/*********************************************************************//**
Checks if some other transaction has a lock request in the queue.
@return lock or NULL */
const lock_t*
lock_rec_other_has_expl_req(
/*========================*/
	lock_mode		mode,	/*!< in: LOCK_S or LOCK_X */
	const buf_block_t*	block,	/*!< in: buffer block containing
					the record */
	bool			wait,	/*!< in: whether also waiting locks
					are taken into account */
	ulint			heap_no,/*!< in: heap number of the record */
	const trx_t*		trx)	/*!< in: transaction, or NULL if
					requests by all transactions
					are taken into account */
{

	ut_ad(lock_mutex_own());
	ut_ad(mode == LOCK_X || mode == LOCK_S);

	/* Only GAP lock can be on SUPREMUM, and we are not looking for
	GAP lock */
	if (heap_no == PAGE_HEAP_NO_SUPREMUM) {
		return(NULL);
	}

	for (const lock_t* lock = lock_rec_get_first(lock_sys->rec_hash,
						     block, heap_no);
	     lock != NULL;
	     lock = lock_rec_get_next_const(heap_no, lock)) {

		if (lock->trx != trx
		    && !lock_rec_get_gap(lock)
		    && (!wait || !lock_get_wait(lock))
		    && lock_mode_stronger_or_eq(lock_get_mode(lock), mode)) {

			return(lock);
		}
	}

	return(NULL);
}
#endif /* UNIV_DEBUG */

/*********************************************************************//**
Checks if some other transaction has a conflicting explicit lock request
in the queue, so that we have to wait.
@return lock or NULL */
static
const lock_t*
lock_rec_other_has_conflicting(
/*===========================*/
	ulint			mode,	/*!< in: LOCK_S or LOCK_X,
					possibly ORed to LOCK_GAP or
					LOC_REC_NOT_GAP,
					LOCK_INSERT_INTENTION */
	const buf_block_t*	block,	/*!< in: buffer block containing
					the record */
	ulint			heap_no,/*!< in: heap number of the record */
	const trx_t*		trx)	/*!< in: our transaction */
{
	const lock_t*		lock;

	ut_ad(lock_mutex_own());

	bool	is_supremum = (heap_no == PAGE_HEAP_NO_SUPREMUM);

	for (lock = lock_rec_get_first(lock_sys->rec_hash, block, heap_no);
	     lock != NULL;
	     lock = lock_rec_get_next_const(heap_no, lock)) {

		if (lock_rec_has_to_wait(trx, mode, lock, is_supremum)) {
			return(lock);
		}
	}

	return(NULL);
}

/*********************************************************************//**
Checks if some transaction has an implicit x-lock on a record in a secondary
index.
@return transaction id of the transaction which has the x-lock, or 0;
NOTE that this function can return false positives but never false
negatives. The caller must confirm all positive results by calling
trx_is_active(). */
static
trx_t*
lock_sec_rec_some_has_impl(
/*=======================*/
	const rec_t*	rec,	/*!< in: user record */
	dict_index_t*	index,	/*!< in: secondary index */
	const ulint*	offsets)/*!< in: rec_get_offsets(rec, index) */
{
	trx_t*		trx;
	trx_id_t	max_trx_id;
	const page_t*	page = page_align(rec);

	ut_ad(!lock_mutex_own());
	ut_ad(!trx_sys_mutex_own());
	ut_ad(!dict_index_is_clust(index));
	ut_ad(page_rec_is_user_rec(rec));
	ut_ad(rec_offs_validate(rec, index, offsets));

	max_trx_id = page_get_max_trx_id(page);

	/* Some transaction may have an implicit x-lock on the record only
	if the max trx id for the page >= min trx id for the trx list, or
	database recovery is running. We do not write the changes of a page
	max trx id to the log, and therefore during recovery, this value
	for a page may be incorrect. */

	if (max_trx_id < trx_rw_min_trx_id() && !recv_recovery_is_on()) {

		trx = 0;

	} else if (!lock_check_trx_id_sanity(max_trx_id, rec, index, offsets)) {

		buf_page_print(page, univ_page_size, 0);

		/* The page is corrupt: try to avoid a crash by returning 0 */
		trx = 0;

	/* In this case it is possible that some transaction has an implicit
	x-lock. We have to look in the clustered index. */

	} else {
		trx = row_vers_impl_x_locked(rec, index, offsets);
	}

	return(trx);
}

#ifdef UNIV_DEBUG
/*********************************************************************//**
Checks if some transaction, other than given trx_id, has an explicit
lock on the given rec, in the given precise_mode.
@return	the transaction, whose id is not equal to trx_id, that has an
explicit lock on the given rec, in the given precise_mode or NULL.*/
static
trx_t*
lock_rec_other_trx_holds_expl(
/*==========================*/
	ulint			precise_mode,	/*!< in: LOCK_S or LOCK_X
						possibly ORed to LOCK_GAP or
						LOCK_REC_NOT_GAP. */
	trx_t*			trx,		/*!< in: trx holding implicit
						lock on rec */
	const rec_t*		rec,		/*!< in: user record */
	const buf_block_t*	block)		/*!< in: buffer block
						containing the record */
{
	trx_t* holds = NULL;

	lock_mutex_enter();

	if (trx_t* impl_trx = trx_rw_is_active(trx->id, NULL, false)) {
		ulint heap_no = page_rec_get_heap_no(rec);
		mutex_enter(&trx_sys->mutex);

		for (trx_t* t = UT_LIST_GET_FIRST(trx_sys->rw_trx_list);
		     t != NULL;
		     t = UT_LIST_GET_NEXT(trx_list, t)) {

			lock_t* expl_lock = lock_rec_has_expl(
				precise_mode, block, heap_no, t);

			if (expl_lock && expl_lock->trx != impl_trx) {
				/* An explicit lock is held by trx other than
				the trx holding the implicit lock. */
				holds = expl_lock->trx;
				break;
			}
		}

		mutex_exit(&trx_sys->mutex);
	}

	lock_mutex_exit();

	return(holds);
}
#endif /* UNIV_DEBUG */

/*********************************************************************//**
Return approximate number or record locks (bits set in the bitmap) for
this transaction. Since delete-marked records may be removed, the
record count will not be precise.
The caller must be holding lock_sys->mutex. */
ulint
lock_number_of_rows_locked(
/*=======================*/
	const trx_lock_t*	trx_lock)	/*!< in: transaction locks */
{
	ut_ad(lock_mutex_own());

	return(trx_lock->n_rec_locks);
}

/*********************************************************************//**
Return the number of table locks for a transaction.
The caller must be holding lock_sys->mutex. */
ulint
lock_number_of_tables_locked(
/*=========================*/
	const trx_lock_t*	trx_lock)	/*!< in: transaction locks */
{
	const lock_t*	lock;
	ulint		n_tables = 0;

	ut_ad(lock_mutex_own());

	for (lock = UT_LIST_GET_FIRST(trx_lock->trx_locks);
	     lock != NULL;
	     lock = UT_LIST_GET_NEXT(trx_locks, lock)) {

		if (lock_get_type_low(lock) == LOCK_TABLE) {
			n_tables++;
		}
	}

	return(n_tables);
}

/*============== RECORD LOCK CREATION AND QUEUE MANAGEMENT =============*/

/**
Check of the lock is on m_rec_id.
@param[in] lock			Lock to compare with
@return true if the record lock is on m_rec_id*/
/**
@param[in] rhs			Lock to compare with
@return true if the record lock equals rhs */
bool
RecLock::is_on_row(const lock_t* lock) const
{
	ut_ad(lock_get_type_low(lock) == LOCK_REC);

	const lock_rec_t&	other = lock->un_member.rec_lock;

	return(other.space == m_rec_id.m_space_id
	       && other.page_no == m_rec_id.m_page_no
	       && lock_rec_get_nth_bit(lock, m_rec_id.m_heap_no));
}

/**
Do some checks and prepare for creating a new record lock */
void
RecLock::prepare() const
{
	ut_ad(lock_mutex_own());
	ut_ad(m_trx == thr_get_trx(m_thr));

	/* Test if there already is some other reason to suspend thread:
	we do not enqueue a lock request if the query thread should be
	stopped anyway */

	if (que_thr_stop(m_thr)) {
		ut_error;
	}

	switch (trx_get_dict_operation(m_trx)) {
	case TRX_DICT_OP_NONE:
		break;
	case TRX_DICT_OP_TABLE:
	case TRX_DICT_OP_INDEX:
		ib::error() << "A record lock wait happens in a dictionary"
			" operation. index " << m_index->name
			<< " of table " << m_index->table->name
			<< ". " << BUG_REPORT_MSG;
		ut_ad(0);
	}

	ut_ad(m_index->table->n_ref_count > 0
	      || !m_index->table->can_be_evicted);
}

/**
Create the lock instance
@param[in, out] trx	The transaction requesting the lock
@param[in, out] index	Index on which record lock is required
@param[in] mode		The lock mode desired
@param[in] rec_id	The record id
@param[in] size		Size of the lock + bitmap requested
@return a record lock instance */
lock_t*
RecLock::lock_alloc(
	trx_t*		trx,
	dict_index_t*	index,
	ulint		mode,
	const RecID&	rec_id,
	ulint		size)
{
	ut_ad(lock_mutex_own());

	lock_t*	lock;

	if (trx->lock.rec_cached >= trx->lock.rec_pool.size()
	    || sizeof(*lock) + size > REC_LOCK_SIZE) {

		ulint		n_bytes = size + sizeof(*lock);
		mem_heap_t*	heap = trx->lock.lock_heap;

		lock = reinterpret_cast<lock_t*>(mem_heap_alloc(heap, n_bytes));
	} else {

		lock = trx->lock.rec_pool[trx->lock.rec_cached];
		++trx->lock.rec_cached;
	}

	lock->trx = trx;

	lock->index = index;

	/* Setup the lock attributes */

	lock->type_mode = LOCK_REC | (mode & ~LOCK_TYPE_MASK);

	lock_rec_t&	rec_lock = lock->un_member.rec_lock;

	/* Predicate lock always on INFIMUM (0) */

	if (is_predicate_lock(mode)) {

		rec_lock.n_bits = 8;

		memset(&lock[1], 0x0, 1);

	} else {
		ut_ad(8 * size < UINT32_MAX);
		rec_lock.n_bits = static_cast<uint32_t>(8 * size);

		memset(&lock[1], 0x0, size);
	}

	rec_lock.space = rec_id.m_space_id;

	rec_lock.page_no = rec_id.m_page_no;

	/* Set the bit corresponding to rec */

	lock_rec_set_nth_bit(lock, rec_id.m_heap_no);

	MONITOR_INC(MONITOR_NUM_RECLOCK);

	MONITOR_INC(MONITOR_RECLOCK_CREATED);

	return(lock);
}

/**
Add the lock to the record lock hash and the transaction's lock list
@param[in,out] lock	Newly created record lock to add to the rec hash
@param[in] add_to_hash	If the lock should be added to the hash table */
void
RecLock::lock_add(lock_t* lock, bool add_to_hash)
{
	ut_ad(lock_mutex_own());
	ut_ad(trx_mutex_own(lock->trx));

	if (add_to_hash) {
		ulint	key = m_rec_id.fold();

		++lock->index->table->n_rec_locks;

		HASH_INSERT(lock_t, hash, lock_hash_get(m_mode), key, lock);
	}

	if (m_mode & LOCK_WAIT) {
		lock_set_lock_and_trx_wait(lock, lock->trx);
	}

	UT_LIST_ADD_LAST(lock->trx->lock.trx_locks, lock);
}

/**
Create a new lock.
@param[in,out] trx		Transaction requesting the lock
@param[in] owns_trx_mutex	true if caller owns the trx_t::mutex
@param[in] prdt			Predicate lock (optional)
@return a new lock instance */
lock_t*
RecLock::create(trx_t* trx, bool owns_trx_mutex, const lock_prdt_t* prdt)
{
	ut_ad(lock_mutex_own());
	ut_ad(owns_trx_mutex == trx_mutex_own(trx));

	/* Create the explicit lock instance and initialise it. */

	lock_t*	lock = lock_alloc(trx, m_index, m_mode, m_rec_id, m_size);

	if (prdt != NULL && (m_mode & LOCK_PREDICATE)) {

		lock_prdt_set_prdt(lock, prdt);
	}

	/* Ensure that another transaction doesn't access the trx
	lock state and lock data structures while we are adding the
	lock and changing the transaction state to LOCK_WAIT */

	if (!owns_trx_mutex) {
		trx_mutex_enter(trx);
	}

	lock_add(lock, true);

	if (!owns_trx_mutex) {
		trx_mutex_exit(trx);
	}

	return(lock);
}

/**
Check the outcome of the deadlock check
@param[in,out] victim_trx	Transaction selected for rollback
@param[in,out] lock		Lock being requested
@return DB_LOCK_WAIT, DB_DEADLOCK or DB_SUCCESS_LOCKED_REC */
dberr_t
RecLock::check_deadlock_result(const trx_t* victim_trx, lock_t* lock)
{
	ut_ad(lock_mutex_own());
	ut_ad(m_trx == lock->trx);
	ut_ad(trx_mutex_own(m_trx));

	if (victim_trx != NULL) {

		ut_ad(victim_trx == m_trx);

		lock_reset_lock_and_trx_wait(lock);

		lock_rec_reset_nth_bit(lock, m_rec_id.m_heap_no);

		return(DB_DEADLOCK);

	} else if (m_trx->lock.wait_lock == NULL) {

		/* If there was a deadlock but we chose another
		transaction as a victim, it is possible that we
		already have the lock now granted! */

		return(DB_SUCCESS_LOCKED_REC);
	}

	return(DB_LOCK_WAIT);
}

/**
Check and resolve any deadlocks
@param[in, out] lock		The lock being acquired
@return DB_LOCK_WAIT, DB_DEADLOCK, or DB_QUE_THR_SUSPENDED, or
	DB_SUCCESS_LOCKED_REC; DB_SUCCESS_LOCKED_REC means that
	there was a deadlock, but another transaction was chosen
	as a victim, and we got the lock immediately: no need to
	wait then */
dberr_t
RecLock::deadlock_check(lock_t* lock)
{
	ut_ad(lock_mutex_own());
	ut_ad(lock->trx == m_trx);
	ut_ad(trx_mutex_own(m_trx));

	/* This is safe, because DeadlockChecker::check_and_resolve()
	is invoked when a lock wait is enqueued for the currently
	running transaction. Because m_trx is a running transaction
	(it is not currently suspended because of a lock wait),
	its state can only be changed by this thread, which is
	currently associated with the transaction. */

	trx_mutex_exit(m_trx);

	const trx_t*	victim_trx;

	victim_trx = DeadlockChecker::check_and_resolve(lock, m_trx);

	trx_mutex_enter(m_trx);

	/* Check the outcome of the deadlock test. It is possible that
	the transaction that blocked our lock was rolled back and we
	were granted our lock. */

	dberr_t	err = check_deadlock_result(victim_trx, lock);

	if (err == DB_LOCK_WAIT) {

		set_wait_state(lock);

		MONITOR_INC(MONITOR_LOCKREC_WAIT);
	}

	return(err);
}

/**
Rollback the transaction that is blocking the requesting transaction
@param[in, out] lock	The blocking lock */
void
RecLock::rollback_blocking_trx(lock_t* lock) const
{
	ut_ad(lock_mutex_own());
	ut_ad(m_trx != lock->trx);
	ut_ad(!trx_mutex_own(m_trx));
	ut_ad(lock->trx->lock.que_state == TRX_QUE_LOCK_WAIT);

	lock->trx->lock.was_chosen_as_deadlock_victim = true;

	/* Remove the blocking transaction from the hit list. */
	m_trx->hit_list.remove(hit_list_t::value_type(lock->trx));

	lock_cancel_waiting_and_release(lock);
}

/**
Collect the transactions that will need to be rolled back asynchronously
@param[in, out] trx	Transaction to be rolled back */
void
RecLock::mark_trx_for_rollback(trx_t* trx)
{
	trx->abort = true;

	ut_ad(!trx->read_only);
	ut_ad(trx_mutex_own(m_trx));
	ut_ad(!(trx->in_innodb & TRX_FORCE_ROLLBACK));
	ut_ad(!(trx->in_innodb & TRX_FORCE_ROLLBACK_ASYNC));
	ut_ad(!(trx->in_innodb & TRX_FORCE_ROLLBACK_DISABLE));

	/* Note that we will attempt an async rollback. The _ASYNC
	flag will be cleared if the transaction is rolled back
	synchronously before we get a chance to do it. */

	trx->in_innodb |= TRX_FORCE_ROLLBACK | TRX_FORCE_ROLLBACK_ASYNC;

	bool		cas;
	os_thread_id_t	thread_id = os_thread_get_curr_id();

	cas = os_compare_and_swap_thread_id(&trx->killed_by, 0, thread_id);

	ut_a(cas);

	m_trx->hit_list.push_back(hit_list_t::value_type(trx));

	THD*	thd = trx->mysql_thd;

	if (thd != NULL) {

		char	buffer[1024];

		ib::info() << "Blocking transaction: ID: " << trx->id << " - "
			<< thd_security_context(thd, buffer, sizeof(buffer),
						512);
	}
}

/**
Add the lock to the head of the record lock {space, page_no} wait queue and
the transaction's lock list. If the transactions holding blocking locks are
already marked for termination then they are not added to the hit list.

@param[in, out] lock		Lock being requested
@param[in, out] wait_for	The blocking lock
@param[in] kill_trx		true if the transaction that m_trx is waiting
				for should be killed */
void
RecLock::jump_queue(lock_t* lock, const lock_t* wait_for, bool kill_trx)
{
	ut_ad(m_trx == lock->trx);
	ut_ad(trx_mutex_own(m_trx));
	ut_ad(wait_for->trx != m_trx);
	ut_ad(trx_is_high_priority(m_trx));
	ut_ad(m_rec_id.m_heap_no != ULINT32_UNDEFINED);

	/* We need to change the hash bucket list pointers only. */

	lock_t*	head = const_cast<lock_t*>(wait_for);

	/* If it is already marked for asynchronous rollback, we don't
	roll it back */

	if (kill_trx && !wait_for->trx->abort) {

		mark_trx_for_rollback(wait_for->trx);
	}

	/* H -> T => H -> Lock -> T */
	lock->hash = head->hash;
	head->hash = lock;

	++lock->index->table->n_rec_locks;

	typedef std::set<trx_t*> Trxs;

	Trxs	trxs;

	/* Locks ahead in the queue need to be rolled back */

	for (lock_t* next = lock->hash; next != NULL; next = next->hash) {

		trx_t*		trx = next->trx;

		if (!is_on_row(next)
		    || (trx->lock.que_state == TRX_QUE_LOCK_WAIT
			&& trx->lock.wait_lock == next)
		    || trx->read_only
		    || trx == lock->trx
		    || trx == wait_for->trx) {

			continue;
		}

		ut_ad(next != lock);
		ut_ad(next != wait_for);

		Trxs::iterator	it;

		/* If the transaction is waiting on some other lock.
		The abort state cannot change while we hold the lock
		sys mutex.

		There is one loose end. We are ignoring transactions
		that are marked for abort by some other transaction.
		We have to be careful that the other transaction must
		kill these (skipped) transactions, ie. it cannot be
		interrupted before it acts on the trx_t::hit_list.

		If the aborted transactions are not killed the worst
		case should be that the high priority transaction
		ends up waiting, it should not affect correctness. */

		trx_mutex_enter(trx);

		if (!trx->abort
		    && (trx->in_innodb & TRX_FORCE_ROLLBACK_DISABLE) == 0
		    && (it = trxs.find(trx)) == trxs.end()) {

			mark_trx_for_rollback(trx);

			trxs.insert(it, trx);
		}

		trx_mutex_exit(trx);
	}
}

/**
Setup the requesting transaction state for lock grant
@param[in,out] lock		Lock for which to change state */
void
RecLock::set_wait_state(lock_t* lock)
{
	ut_ad(lock_mutex_own());
	ut_ad(m_trx == lock->trx);
	ut_ad(trx_mutex_own(m_trx));
	ut_ad(lock_get_wait(lock));

	m_trx->lock.wait_started = ut_time();

	m_trx->lock.que_state = TRX_QUE_LOCK_WAIT;

	m_trx->lock.was_chosen_as_deadlock_victim = false;

	bool	stopped = que_thr_stop(m_thr);
	ut_a(stopped);
}

/**
Enqueue a lock wait for a high priority transaction, jump the record lock
wait queue and if the transaction at the head of the queue is itself waiting
roll it back.
@param[in, out] wait_for	The lock that the the joining transaction is
				waiting for
@return NULL if the lock was granted */
lock_t*
RecLock::enqueue_priority(const lock_t* wait_for, const lock_prdt_t* prdt)
{
	/* Create the explicit lock instance and initialise it. */

	lock_t*	lock = lock_alloc(m_trx, m_index, m_mode, m_rec_id, m_size);

	if (prdt != NULL && (m_mode & LOCK_PREDICATE)) {

		lock_prdt_set_prdt(lock, prdt);
	}

	trx_mutex_enter(wait_for->trx);

#ifdef UNIV_DEBUG
	ulint	version = wait_for->trx->version;
#endif /* UNIV_DEBUG */

	bool	read_only = wait_for->trx->read_only;

	bool	waiting = wait_for->trx->lock.que_state == TRX_QUE_LOCK_WAIT;

	/* If the transaction that is blocking m_trx is itself waiting then
	we kill it in this method, unless it is waiting for the same lock
	that m_trx wants. For the latter case we kill it before doing the
	lock wait.

	If the transaction is not waiting but is a read-only transaction
	started with START TRANSACTION READ ONLY then we wait for it. */

	bool	kill_trx;

	if (waiting) {

		ut_ad(wait_for->trx->lock.wait_lock != NULL);

		/* Check if "wait_for" trx is waiting for the same lock
		and we can roll it back asynchronously. */

		kill_trx = wait_for->trx->lock.wait_lock != wait_for
			   && !read_only
			   && !(wait_for->trx->in_innodb
				& TRX_FORCE_ROLLBACK_DISABLE);

	} else if (read_only) {

		/* Wait for running read-only transactions */

		kill_trx = false;

	} else {

		/* Rollback any running non-ro blocking transactions */

		kill_trx = !(wait_for->trx->in_innodb
			     & TRX_FORCE_ROLLBACK_DISABLE);
	}

	/* Move the lock being requested to the head of
	the wait queue so that if the transaction that
	we are waiting for is rolled back we get dibs
	on the row. */

	jump_queue(lock, wait_for, kill_trx);


	/* Only if the blocking transaction is itself waiting, but
	waiting on a different lock we do the rollback here. For active
	transactions we do the rollback before we enter lock wait. */

	if (waiting && kill_trx) {

		UT_LIST_ADD_LAST(m_trx->lock.trx_locks, lock);

		set_wait_state(lock);

		lock_set_lock_and_trx_wait(lock, m_trx);

		trx_mutex_exit(m_trx);

		/* Rollback the transaction that is blocking us. It should
		be the one that is at the head of the queue. Note this
		doesn't guarantee that our lock will be granted. We will kill
		other blocking transactions later in trx_kill_blocking(). */

		rollback_blocking_trx(wait_for->trx->lock.wait_lock);

		trx_mutex_exit(wait_for->trx);

		/* This state should not change even if we release the
		wait_for->trx->mutex. These can only change if we release
		the lock_sys_t::mutex.  */

		ut_ad(version == wait_for->trx->version);
		ut_ad(read_only == wait_for->trx->read_only);

		trx_mutex_enter(m_trx);

		/* There is no guaranteed that the lock will have been granted
		even if we were the first in the queue. There could be other
		transactions that hold e.g., a granted S lock but are waiting
		for another lock. They will be rolled back later. */

		return(lock_get_wait(lock) ? lock : NULL);

	} else {

		trx_mutex_exit(wait_for->trx);

		lock_add(lock, false);
	}

	/* This state should not change even if we release the
	wait_for->trx->mutex. These can only change if we release
	the lock_sys_t::mutex.  */

	ut_ad(version == wait_for->trx->version);
	ut_ad(read_only == wait_for->trx->read_only);

	return(lock);
}

/**
Enqueue a lock wait for normal transaction. If it is a high priority transaction
then jump the record lock wait queue and if the transaction at the head of the
queue is itself waiting roll it back, also do a deadlock check and resolve.
@param[in, out] wait_for	The lock that the joining transaction is
				waiting for
@param[in] prdt			Predicate [optional]
@return DB_LOCK_WAIT, DB_DEADLOCK, or DB_QUE_THR_SUSPENDED, or
	DB_SUCCESS_LOCKED_REC; DB_SUCCESS_LOCKED_REC means that
	there was a deadlock, but another transaction was chosen
	as a victim, and we got the lock immediately: no need to
	wait then */
dberr_t
RecLock::add_to_waitq(const lock_t* wait_for, const lock_prdt_t* prdt)
{
	ut_ad(lock_mutex_own());
	ut_ad(m_trx == thr_get_trx(m_thr));
	ut_ad(trx_mutex_own(m_trx));

	DEBUG_SYNC_C("rec_lock_add_to_waitq");

	m_mode |= LOCK_WAIT;

	/* Do the preliminary checks, and set query thread state */

	prepare();

	lock_t*		lock;
	const trx_t*	victim_trx;

	/* We don't rollback internal (basically background statistics
	gathering) transactions. The problem is that we don't currently
	block them using the TrxInInnoDB() mechanism. */

	if (wait_for->trx->mysql_thd == NULL) {

		victim_trx = NULL;

	} else {

		/* Currently, if both are high priority transactions then
		the requesting transaction will be rolled back. */

		victim_trx = trx_arbitrate(m_trx, wait_for->trx);
	}

	if (victim_trx == m_trx || victim_trx == NULL) {

		/* Ensure that the wait flag is not set. */
		lock = create(m_trx, true, prdt);

		/* If a high priority transaction has been selected as
		a victim there is nothing we can do. */

		if (trx_is_high_priority(m_trx) && victim_trx != NULL) {

			lock_reset_lock_and_trx_wait(lock);

			lock_rec_reset_nth_bit(lock, m_rec_id.m_heap_no);

			if (victim_trx->mysql_thd != NULL) {
				char	buffer[1024];
				THD*	thd = victim_trx->mysql_thd;

				ib::info() << "High priority transaction"
					" selected for rollback : "
					<< thd_security_context(
						thd, buffer, sizeof(buffer),
						512);
			}

			return(DB_DEADLOCK);
		}

	} else if ((lock = enqueue_priority(wait_for, prdt)) == NULL) {

		/* Lock was granted */
		return(DB_SUCCESS);
	}

	ut_ad(lock_get_wait(lock));

	dberr_t	err = deadlock_check(lock);

	ut_ad(trx_mutex_own(m_trx));

	return(err);
}

/*********************************************************************//**
Adds a record lock request in the record queue. The request is normally
added as the last in the queue, but if there are no waiting lock requests
on the record, and the request to be added is not a waiting request, we
can reuse a suitable record lock object already existing on the same page,
just setting the appropriate bit in its bitmap. This is a low-level function
which does NOT check for deadlocks or lock compatibility!
@return lock where the bit was set */
static
void
lock_rec_add_to_queue(
/*==================*/
	ulint			type_mode,/*!< in: lock mode, wait, gap
					etc. flags; type is ignored
					and replaced by LOCK_REC */
	const buf_block_t*	block,	/*!< in: buffer block containing
					the record */
	ulint			heap_no,/*!< in: heap number of the record */
	dict_index_t*		index,	/*!< in: index of record */
	trx_t*			trx,	/*!< in/out: transaction */
	bool			caller_owns_trx_mutex)
					/*!< in: TRUE if caller owns the
					transaction mutex */
{
#ifdef UNIV_DEBUG
	ut_ad(lock_mutex_own());
	ut_ad(caller_owns_trx_mutex == trx_mutex_own(trx));
	ut_ad(dict_index_is_clust(index)
	      || dict_index_get_online_status(index) != ONLINE_INDEX_CREATION);
	switch (type_mode & LOCK_MODE_MASK) {
	case LOCK_X:
	case LOCK_S:
		break;
	default:
		ut_error;
	}

	if (!(type_mode & (LOCK_WAIT | LOCK_GAP))) {
		lock_mode	mode = (type_mode & LOCK_MODE_MASK) == LOCK_S
			? LOCK_X
			: LOCK_S;
		const lock_t*	other_lock
			= lock_rec_other_has_expl_req(
				mode, block, false, heap_no, trx);
		ut_a(!other_lock);
	}
#endif /* UNIV_DEBUG */

	type_mode |= LOCK_REC;

	/* If rec is the supremum record, then we can reset the gap bit, as
	all locks on the supremum are automatically of the gap type, and we
	try to avoid unnecessary memory consumption of a new record lock
	struct for a gap type lock */

	if (heap_no == PAGE_HEAP_NO_SUPREMUM) {
		ut_ad(!(type_mode & LOCK_REC_NOT_GAP));

		/* There should never be LOCK_REC_NOT_GAP on a supremum
		record, but let us play safe */

		type_mode &= ~(LOCK_GAP | LOCK_REC_NOT_GAP);
	}

	lock_t*		lock;
	lock_t*		first_lock;
	hash_table_t*	hash = lock_hash_get(type_mode);

	/* Look for a waiting lock request on the same record or on a gap */

	for (first_lock = lock = lock_rec_get_first_on_page(hash, block);
	     lock != NULL;
	     lock = lock_rec_get_next_on_page(lock)) {

		if (lock_get_wait(lock)
		    && lock_rec_get_nth_bit(lock, heap_no)) {

			break;
		}
	}

	if (lock == NULL && !(type_mode & LOCK_WAIT)) {

		/* Look for a similar record lock on the same page:
		if one is found and there are no waiting lock requests,
		we can just set the bit */

		lock = lock_rec_find_similar_on_page(
			type_mode, heap_no, first_lock, trx);

		if (lock != NULL) {

			lock_rec_set_nth_bit(lock, heap_no);

			return;
		}
	}

	RecLock		rec_lock(index, block, heap_no, type_mode);

	rec_lock.create(trx, caller_owns_trx_mutex);
}

/*********************************************************************//**
This is a fast routine for locking a record in the most common cases:
there are no explicit locks on the page, or there is just one lock, owned
by this transaction, and of the right type_mode. This is a low-level function
which does NOT look at implicit locks! Checks lock compatibility within
explicit locks. This function sets a normal next-key lock, or in the case of
a page supremum record, a gap type lock.
@return whether the locking succeeded */
UNIV_INLINE
lock_rec_req_status
lock_rec_lock_fast(
/*===============*/
	bool			impl,	/*!< in: if TRUE, no lock is set
					if no wait is necessary: we
					assume that the caller will
					set an implicit lock */
	ulint			mode,	/*!< in: lock mode: LOCK_X or
					LOCK_S possibly ORed to either
					LOCK_GAP or LOCK_REC_NOT_GAP */
	const buf_block_t*	block,	/*!< in: buffer block containing
					the record */
	ulint			heap_no,/*!< in: heap number of record */
	dict_index_t*		index,	/*!< in: index of record */
	que_thr_t*		thr)	/*!< in: query thread */
{
	ut_ad(lock_mutex_own());
	ut_ad(!srv_read_only_mode);
	ut_ad((LOCK_MODE_MASK & mode) != LOCK_S
	      || lock_table_has(thr_get_trx(thr), index->table, LOCK_IS));
	ut_ad((LOCK_MODE_MASK & mode) != LOCK_X
	      || lock_table_has(thr_get_trx(thr), index->table, LOCK_IX)
	      || srv_read_only_mode);
	ut_ad((LOCK_MODE_MASK & mode) == LOCK_S
	      || (LOCK_MODE_MASK & mode) == LOCK_X);
	ut_ad(mode - (LOCK_MODE_MASK & mode) == LOCK_GAP
	      || mode - (LOCK_MODE_MASK & mode) == 0
	      || mode - (LOCK_MODE_MASK & mode) == LOCK_REC_NOT_GAP);
	ut_ad(dict_index_is_clust(index) || !dict_index_is_online_ddl(index));

	DBUG_EXECUTE_IF("innodb_report_deadlock", return(LOCK_REC_FAIL););

	lock_t*	lock = lock_rec_get_first_on_page(lock_sys->rec_hash, block);

	trx_t*	trx = thr_get_trx(thr);

	lock_rec_req_status	status = LOCK_REC_SUCCESS;

	if (lock == NULL) {

		if (!impl) {
			RecLock	rec_lock(index, block, heap_no, mode);

			/* Note that we don't own the trx mutex. */
			rec_lock.create(trx, false);
		}

		status = LOCK_REC_SUCCESS_CREATED;
	} else {
		trx_mutex_enter(trx);

		if (lock_rec_get_next_on_page(lock)
		     || lock->trx != trx
		     || lock->type_mode != (mode | LOCK_REC)
		     || lock_rec_get_n_bits(lock) <= heap_no) {

			status = LOCK_REC_FAIL;
		} else if (!impl) {
			/* If the nth bit of the record lock is already set
			then we do not set a new lock bit, otherwise we do
			set */
			if (!lock_rec_get_nth_bit(lock, heap_no)) {
				lock_rec_set_nth_bit(lock, heap_no);
				status = LOCK_REC_SUCCESS_CREATED;
			}
		}

		trx_mutex_exit(trx);
	}

	return(status);
}

/*********************************************************************//**
This is the general, and slower, routine for locking a record. This is a
low-level function which does NOT look at implicit locks! Checks lock
compatibility within explicit locks. This function sets a normal next-key
lock, or in the case of a page supremum record, a gap type lock.
@return DB_SUCCESS, DB_SUCCESS_LOCKED_REC, DB_LOCK_WAIT, DB_DEADLOCK,
or DB_QUE_THR_SUSPENDED */
static
dberr_t
lock_rec_lock_slow(
/*===============*/
	ibool			impl,	/*!< in: if TRUE, no lock is set
					if no wait is necessary: we
					assume that the caller will
					set an implicit lock */
	ulint			mode,	/*!< in: lock mode: LOCK_X or
					LOCK_S possibly ORed to either
					LOCK_GAP or LOCK_REC_NOT_GAP */
	const buf_block_t*	block,	/*!< in: buffer block containing
					the record */
	ulint			heap_no,/*!< in: heap number of record */
	dict_index_t*		index,	/*!< in: index of record */
	que_thr_t*		thr)	/*!< in: query thread */
{
	ut_ad(lock_mutex_own());
	ut_ad(!srv_read_only_mode);
	ut_ad((LOCK_MODE_MASK & mode) != LOCK_S
	      || lock_table_has(thr_get_trx(thr), index->table, LOCK_IS));
	ut_ad((LOCK_MODE_MASK & mode) != LOCK_X
	      || lock_table_has(thr_get_trx(thr), index->table, LOCK_IX));
	ut_ad((LOCK_MODE_MASK & mode) == LOCK_S
	      || (LOCK_MODE_MASK & mode) == LOCK_X);
	ut_ad(mode - (LOCK_MODE_MASK & mode) == LOCK_GAP
	      || mode - (LOCK_MODE_MASK & mode) == 0
	      || mode - (LOCK_MODE_MASK & mode) == LOCK_REC_NOT_GAP);
	ut_ad(dict_index_is_clust(index) || !dict_index_is_online_ddl(index));

	DBUG_EXECUTE_IF("innodb_report_deadlock", return(DB_DEADLOCK););

	dberr_t	err;
	trx_t*	trx = thr_get_trx(thr);

	trx_mutex_enter(trx);

	if (lock_rec_has_expl(mode, block, heap_no, trx)) {

		/* The trx already has a strong enough lock on rec: do
		nothing */

		err = DB_SUCCESS;

	} else {

		const lock_t* wait_for = lock_rec_other_has_conflicting(
			mode, block, heap_no, trx);

		if (wait_for != NULL) {

			/* If another transaction has a non-gap conflicting
			request in the queue, as this transaction does not
			have a lock strong enough already granted on the
			record, we may have to wait. */

			RecLock	rec_lock(thr, index, block, heap_no, mode);

			err = rec_lock.add_to_waitq(wait_for);

		} else if (!impl) {

			/* Set the requested lock on the record, note that
			we already own the transaction mutex. */

			lock_rec_add_to_queue(
				LOCK_REC | mode, block, heap_no, index, trx,
				true);

			err = DB_SUCCESS_LOCKED_REC;
		} else {
			err = DB_SUCCESS;
		}
	}

	trx_mutex_exit(trx);

	return(err);
}

/*********************************************************************//**
Tries to lock the specified record in the mode requested. If not immediately
possible, enqueues a waiting lock request. This is a low-level function
which does NOT look at implicit locks! Checks lock compatibility within
explicit locks. This function sets a normal next-key lock, or in the case
of a page supremum record, a gap type lock.
@return DB_SUCCESS, DB_SUCCESS_LOCKED_REC, DB_LOCK_WAIT, DB_DEADLOCK,
or DB_QUE_THR_SUSPENDED */
static
dberr_t
lock_rec_lock(
/*==========*/
	bool			impl,	/*!< in: if true, no lock is set
					if no wait is necessary: we
					assume that the caller will
					set an implicit lock */
	ulint			mode,	/*!< in: lock mode: LOCK_X or
					LOCK_S possibly ORed to either
					LOCK_GAP or LOCK_REC_NOT_GAP */
	const buf_block_t*	block,	/*!< in: buffer block containing
					the record */
	ulint			heap_no,/*!< in: heap number of record */
	dict_index_t*		index,	/*!< in: index of record */
	que_thr_t*		thr)	/*!< in: query thread */
{
	ut_ad(lock_mutex_own());
	ut_ad(!srv_read_only_mode);
	ut_ad((LOCK_MODE_MASK & mode) != LOCK_S
	      || lock_table_has(thr_get_trx(thr), index->table, LOCK_IS));
	ut_ad((LOCK_MODE_MASK & mode) != LOCK_X
	      || lock_table_has(thr_get_trx(thr), index->table, LOCK_IX));
	ut_ad((LOCK_MODE_MASK & mode) == LOCK_S
	      || (LOCK_MODE_MASK & mode) == LOCK_X);
	ut_ad(mode - (LOCK_MODE_MASK & mode) == LOCK_GAP
	      || mode - (LOCK_MODE_MASK & mode) == LOCK_REC_NOT_GAP
	      || mode - (LOCK_MODE_MASK & mode) == 0);
	ut_ad(dict_index_is_clust(index) || !dict_index_is_online_ddl(index));

	/* We try a simplified and faster subroutine for the most
	common cases */
	switch (lock_rec_lock_fast(impl, mode, block, heap_no, index, thr)) {
	case LOCK_REC_SUCCESS:
		return(DB_SUCCESS);
	case LOCK_REC_SUCCESS_CREATED:
		return(DB_SUCCESS_LOCKED_REC);
	case LOCK_REC_FAIL:
		return(lock_rec_lock_slow(impl, mode, block,
					  heap_no, index, thr));
	}

	ut_error;
	return(DB_ERROR);
}

/*********************************************************************//**
Checks if a waiting record lock request still has to wait in a queue.
@return lock that is causing the wait */
static
const lock_t*
lock_rec_has_to_wait_in_queue(
/*==========================*/
	const lock_t*	wait_lock)	/*!< in: waiting record lock */
{
	const lock_t*	lock;
	ulint		space;
	ulint		page_no;
	ulint		heap_no;
	ulint		bit_mask;
	ulint		bit_offset;
	hash_table_t*	hash;

	ut_ad(lock_mutex_own());
	ut_ad(lock_get_wait(wait_lock));
	ut_ad(lock_get_type_low(wait_lock) == LOCK_REC);

	space = wait_lock->un_member.rec_lock.space;
	page_no = wait_lock->un_member.rec_lock.page_no;
	heap_no = lock_rec_find_set_bit(wait_lock);

	bit_offset = heap_no / 8;
	bit_mask = static_cast<ulint>(1 << (heap_no % 8));

	hash = lock_hash_get(wait_lock->type_mode);

	for (lock = lock_rec_get_first_on_page_addr(hash, space, page_no);
	     lock != wait_lock;
	     lock = lock_rec_get_next_on_page_const(lock)) {

		const byte*	p = (const byte*) &lock[1];

		if (heap_no < lock_rec_get_n_bits(lock)
		    && (p[bit_offset] & bit_mask)
		    && lock_has_to_wait(wait_lock, lock)) {

			return(lock);
		}
	}

	return(NULL);
}

/*************************************************************//**
Grants a lock to a waiting lock request and releases the waiting transaction.
The caller must hold lock_sys->mutex but not lock->trx->mutex. */
static
void
lock_grant(
/*=======*/
	lock_t*	lock)	/*!< in/out: waiting lock request */
{
	ut_ad(lock_mutex_own());

	lock_reset_lock_and_trx_wait(lock);

	trx_mutex_enter(lock->trx);

	if (lock_get_mode(lock) == LOCK_AUTO_INC) {
		dict_table_t*	table = lock->un_member.tab_lock.table;

		if (table->autoinc_trx == lock->trx) {
			ib::error() << "Transaction already had an"
				<< " AUTO-INC lock!";
		} else {
			table->autoinc_trx = lock->trx;

			ib_vector_push(lock->trx->autoinc_locks, &lock);
		}
	}

	DBUG_PRINT("ib_lock", ("wait for trx " TRX_ID_FMT " ends",
			       trx_get_id_for_print(lock->trx)));

	/* If we are resolving a deadlock by choosing another transaction
	as a victim, then our original transaction may not be in the
	TRX_QUE_LOCK_WAIT state, and there is no need to end the lock wait
	for it */

	if (lock->trx->lock.que_state == TRX_QUE_LOCK_WAIT) {
		que_thr_t*	thr;

		thr = que_thr_end_lock_wait(lock->trx);

		if (thr != NULL) {
			lock_wait_release_thread_if_suspended(thr);
		}
	}

	trx_mutex_exit(lock->trx);
}

/*************************************************************//**
Cancels a waiting record lock request and releases the waiting transaction
that requested it. NOTE: does NOT check if waiting lock requests behind this
one can now be granted! */
static
void
lock_rec_cancel(
/*============*/
	lock_t*	lock)	/*!< in: waiting record lock request */
{
	que_thr_t*	thr;

	ut_ad(lock_mutex_own());
	ut_ad(lock_get_type_low(lock) == LOCK_REC);

	/* Reset the bit (there can be only one set bit) in the lock bitmap */
	lock_rec_reset_nth_bit(lock, lock_rec_find_set_bit(lock));

	/* Reset the wait flag and the back pointer to lock in trx */

	lock_reset_lock_and_trx_wait(lock);

	/* The following function releases the trx from lock wait */

	trx_mutex_enter(lock->trx);

	thr = que_thr_end_lock_wait(lock->trx);

	if (thr != NULL) {
		lock_wait_release_thread_if_suspended(thr);
	}

	trx_mutex_exit(lock->trx);
}

/*************************************************************//**
Removes a record lock request, waiting or granted, from the queue and
grants locks to other transactions in the queue if they now are entitled
to a lock. NOTE: all record locks contained in in_lock are removed. */
void
lock_rec_dequeue_from_page(
/*=======================*/
	lock_t*		in_lock)	/*!< in: record lock object: all
					record locks which are contained in
					this lock object are removed;
					transactions waiting behind will
					get their lock requests granted,
					if they are now qualified to it */
{
	ulint		space;
	ulint		page_no;
	lock_t*		lock;
	trx_lock_t*	trx_lock;
	hash_table_t*	lock_hash;

	ut_ad(lock_mutex_own());
	ut_ad(lock_get_type_low(in_lock) == LOCK_REC);
	/* We may or may not be holding in_lock->trx->mutex here. */

	trx_lock = &in_lock->trx->lock;

	space = in_lock->un_member.rec_lock.space;
	page_no = in_lock->un_member.rec_lock.page_no;

	ut_ad(in_lock->index->table->n_rec_locks > 0);
	in_lock->index->table->n_rec_locks--;

	lock_hash = lock_hash_get(in_lock->type_mode);

	HASH_DELETE(lock_t, hash, lock_hash,
		    lock_rec_fold(space, page_no), in_lock);

	UT_LIST_REMOVE(trx_lock->trx_locks, in_lock);

	MONITOR_INC(MONITOR_RECLOCK_REMOVED);
	MONITOR_DEC(MONITOR_NUM_RECLOCK);

	/* Check if waiting locks in the queue can now be granted: grant
	locks if there are no conflicting locks ahead. Stop at the first
	X lock that is waiting or has been granted. */

	for (lock = lock_rec_get_first_on_page_addr(lock_hash, space, page_no);
	     lock != NULL;
	     lock = lock_rec_get_next_on_page(lock)) {

		if (lock_get_wait(lock)
		    && !lock_rec_has_to_wait_in_queue(lock)) {

			/* Grant the lock */
			ut_ad(lock->trx != in_lock->trx);
			lock_grant(lock);
		}
	}
}

/*************************************************************//**
Removes a record lock request, waiting or granted, from the queue. */
void
lock_rec_discard(
/*=============*/
	lock_t*		in_lock)	/*!< in: record lock object: all
					record locks which are contained
					in this lock object are removed */
{
	ulint		space;
	ulint		page_no;
	trx_lock_t*	trx_lock;

	ut_ad(lock_mutex_own());
	ut_ad(lock_get_type_low(in_lock) == LOCK_REC);

	trx_lock = &in_lock->trx->lock;

	space = in_lock->un_member.rec_lock.space;
	page_no = in_lock->un_member.rec_lock.page_no;

	ut_ad(in_lock->index->table->n_rec_locks > 0);
	in_lock->index->table->n_rec_locks--;

	HASH_DELETE(lock_t, hash, lock_hash_get(in_lock->type_mode),
			    lock_rec_fold(space, page_no), in_lock);

	UT_LIST_REMOVE(trx_lock->trx_locks, in_lock);

	MONITOR_INC(MONITOR_RECLOCK_REMOVED);
	MONITOR_DEC(MONITOR_NUM_RECLOCK);
}

/*************************************************************//**
Removes record lock objects set on an index page which is discarded. This
function does not move locks, or check for waiting locks, therefore the
lock bitmaps must already be reset when this function is called. */
static
void
lock_rec_free_all_from_discard_page_low(
/*====================================*/
	ulint		space,
	ulint		page_no,
	hash_table_t*	lock_hash)
{
	lock_t*	lock;
	lock_t*	next_lock;

	lock = lock_rec_get_first_on_page_addr(lock_hash, space, page_no);

	while (lock != NULL) {
		ut_ad(lock_rec_find_set_bit(lock) == ULINT_UNDEFINED);
		ut_ad(!lock_get_wait(lock));

		next_lock = lock_rec_get_next_on_page(lock);

		lock_rec_discard(lock);

		lock = next_lock;
	}
}

/*************************************************************//**
Removes record lock objects set on an index page which is discarded. This
function does not move locks, or check for waiting locks, therefore the
lock bitmaps must already be reset when this function is called. */
void
lock_rec_free_all_from_discard_page(
/*================================*/
	const buf_block_t*	block)	/*!< in: page to be discarded */
{
	ulint	space;
	ulint	page_no;

	ut_ad(lock_mutex_own());

	space = block->page.id.space();
	page_no = block->page.id.page_no();

	lock_rec_free_all_from_discard_page_low(
		space, page_no, lock_sys->rec_hash);
	lock_rec_free_all_from_discard_page_low(
		space, page_no, lock_sys->prdt_hash);
	lock_rec_free_all_from_discard_page_low(
		space, page_no, lock_sys->prdt_page_hash);
}

/*============= RECORD LOCK MOVING AND INHERITING ===================*/

/*************************************************************//**
Resets the lock bits for a single record. Releases transactions waiting for
lock requests here. */
static
void
lock_rec_reset_and_release_wait_low(
/*================================*/
	hash_table_t*		hash,	/*!< in: hash table */
	const buf_block_t*	block,	/*!< in: buffer block containing
					the record */
	ulint			heap_no)/*!< in: heap number of record */
{
	lock_t*	lock;

	ut_ad(lock_mutex_own());

	for (lock = lock_rec_get_first(hash, block, heap_no);
	     lock != NULL;
	     lock = lock_rec_get_next(heap_no, lock)) {

		if (lock_get_wait(lock)) {
			lock_rec_cancel(lock);
		} else {
			lock_rec_reset_nth_bit(lock, heap_no);
		}
	}
}

/*************************************************************//**
Resets the lock bits for a single record. Releases transactions waiting for
lock requests here. */
static
void
lock_rec_reset_and_release_wait(
/*============================*/
	const buf_block_t*	block,	/*!< in: buffer block containing
					the record */
	ulint			heap_no)/*!< in: heap number of record */
{
	lock_rec_reset_and_release_wait_low(
		lock_sys->rec_hash, block, heap_no);

	lock_rec_reset_and_release_wait_low(
		lock_sys->prdt_hash, block, PAGE_HEAP_NO_INFIMUM);
	lock_rec_reset_and_release_wait_low(
		lock_sys->prdt_page_hash, block, PAGE_HEAP_NO_INFIMUM);
}

/*************************************************************//**
Makes a record to inherit the locks (except LOCK_INSERT_INTENTION type)
of another record as gap type locks, but does not reset the lock bits of
the other record. Also waiting lock requests on rec are inherited as
GRANTED gap locks. */
static
void
lock_rec_inherit_to_gap(
/*====================*/
	const buf_block_t*	heir_block,	/*!< in: block containing the
						record which inherits */
	const buf_block_t*	block,		/*!< in: block containing the
						record from which inherited;
						does NOT reset the locks on
						this record */
	ulint			heir_heap_no,	/*!< in: heap_no of the
						inheriting record */
	ulint			heap_no)	/*!< in: heap_no of the
						donating record */
{
	lock_t*	lock;

	ut_ad(lock_mutex_own());

	/* If srv_locks_unsafe_for_binlog is TRUE or session is using
	READ COMMITTED isolation level, we do not want locks set
	by an UPDATE or a DELETE to be inherited as gap type locks. But we
	DO want S-locks set by a consistency constraint to be inherited also
	then. */

	for (lock = lock_rec_get_first(lock_sys->rec_hash, block, heap_no);
	     lock != NULL;
	     lock = lock_rec_get_next(heap_no, lock)) {

		if (!lock_rec_get_insert_intention(lock)
		    && !((srv_locks_unsafe_for_binlog
			  || lock->trx->isolation_level
			  <= TRX_ISO_READ_COMMITTED)
			 && lock_get_mode(lock) == LOCK_X)) {

			lock_rec_add_to_queue(
				LOCK_REC | LOCK_GAP | lock_get_mode(lock),
				heir_block, heir_heap_no, lock->index,
				lock->trx, FALSE);
		}
	}
}

/*************************************************************//**
Makes a record to inherit the gap locks (except LOCK_INSERT_INTENTION type)
of another record as gap type locks, but does not reset the lock bits of the
other record. Also waiting lock requests are inherited as GRANTED gap locks. */
static
void
lock_rec_inherit_to_gap_if_gap_lock(
/*================================*/
	const buf_block_t*	block,		/*!< in: buffer block */
	ulint			heir_heap_no,	/*!< in: heap_no of
						record which inherits */
	ulint			heap_no)	/*!< in: heap_no of record
						from which inherited;
						does NOT reset the locks
						on this record */
{
	lock_t*	lock;

	lock_mutex_enter();

	for (lock = lock_rec_get_first(lock_sys->rec_hash, block, heap_no);
	     lock != NULL;
	     lock = lock_rec_get_next(heap_no, lock)) {

		if (!lock_rec_get_insert_intention(lock)
		    && (heap_no == PAGE_HEAP_NO_SUPREMUM
			|| !lock_rec_get_rec_not_gap(lock))) {

			lock_rec_add_to_queue(
				LOCK_REC | LOCK_GAP | lock_get_mode(lock),
				block, heir_heap_no, lock->index,
				lock->trx, FALSE);
		}
	}

	lock_mutex_exit();
}

/*************************************************************//**
Moves the locks of a record to another record and resets the lock bits of
the donating record. */
void
lock_rec_move_low(
/*==============*/
	hash_table_t*		lock_hash,	/*!< in: hash table to use */
	const buf_block_t*	receiver,	/*!< in: buffer block containing
						the receiving record */
	const buf_block_t*	donator,	/*!< in: buffer block containing
						the donating record */
	ulint			receiver_heap_no,/*!< in: heap_no of the record
						which gets the locks; there
						must be no lock requests
						on it! */
	ulint			donator_heap_no)/*!< in: heap_no of the record
						which gives the locks */
{
	lock_t*	lock;

	ut_ad(lock_mutex_own());

	/* If the lock is predicate lock, it resides on INFIMUM record */
	ut_ad(lock_rec_get_first(
		lock_hash, receiver, receiver_heap_no) == NULL
	      || lock_hash == lock_sys->prdt_hash
	      || lock_hash == lock_sys->prdt_page_hash);

	for (lock = lock_rec_get_first(lock_hash,
				       donator, donator_heap_no);
	     lock != NULL;
	     lock = lock_rec_get_next(donator_heap_no, lock)) {

		const ulint	type_mode = lock->type_mode;

		lock_rec_reset_nth_bit(lock, donator_heap_no);

		if (type_mode & LOCK_WAIT) {
			lock_reset_lock_and_trx_wait(lock);
		}

		/* Note that we FIRST reset the bit, and then set the lock:
		the function works also if donator == receiver */

		lock_rec_add_to_queue(
			type_mode, receiver, receiver_heap_no,
			lock->index, lock->trx, FALSE);
	}

	ut_ad(lock_rec_get_first(lock_sys->rec_hash,
				 donator, donator_heap_no) == NULL);
}

/*************************************************************//**
Updates the lock table when we have reorganized a page. NOTE: we copy
also the locks set on the infimum of the page; the infimum may carry
locks if an update of a record is occurring on the page, and its locks
were temporarily stored on the infimum. */
void
lock_move_reorganize_page(
/*======================*/
	const buf_block_t*	block,	/*!< in: old index page, now
					reorganized */
	const buf_block_t*	oblock)	/*!< in: copy of the old, not
					reorganized page */
{
	lock_t*		lock;
	UT_LIST_BASE_NODE_T(lock_t)	old_locks;
	mem_heap_t*	heap		= NULL;
	ulint		comp;

	lock_mutex_enter();

	/* FIXME: This needs to deal with predicate lock too */
	lock = lock_rec_get_first_on_page(lock_sys->rec_hash, block);

	if (lock == NULL) {
		lock_mutex_exit();

		return;
	}

	heap = mem_heap_create(256);

	/* Copy first all the locks on the page to heap and reset the
	bitmaps in the original locks; chain the copies of the locks
	using the trx_locks field in them. */

	UT_LIST_INIT(old_locks, &lock_t::trx_locks);

	do {
		/* Make a copy of the lock */
		lock_t*	old_lock = lock_rec_copy(lock, heap);

		UT_LIST_ADD_LAST(old_locks, old_lock);

		/* Reset bitmap of lock */
		lock_rec_bitmap_reset(lock);

		if (lock_get_wait(lock)) {

			lock_reset_lock_and_trx_wait(lock);
		}

		lock = lock_rec_get_next_on_page(lock);
	} while (lock != NULL);

	comp = page_is_comp(block->frame);
	ut_ad(comp == page_is_comp(oblock->frame));

	for (lock = UT_LIST_GET_FIRST(old_locks); lock;
	     lock = UT_LIST_GET_NEXT(trx_locks, lock)) {
		/* NOTE: we copy also the locks set on the infimum and
		supremum of the page; the infimum may carry locks if an
		update of a record is occurring on the page, and its locks
		were temporarily stored on the infimum */
		const rec_t*	rec1 = page_get_infimum_rec(
			buf_block_get_frame(block));
		const rec_t*	rec2 = page_get_infimum_rec(
			buf_block_get_frame(oblock));

		/* Set locks according to old locks */
		for (;;) {
			ulint	old_heap_no;
			ulint	new_heap_no;

			if (comp) {
				old_heap_no = rec_get_heap_no_new(rec2);
				new_heap_no = rec_get_heap_no_new(rec1);

				rec1 = page_rec_get_next_low(rec1, TRUE);
				rec2 = page_rec_get_next_low(rec2, TRUE);
			} else {
				old_heap_no = rec_get_heap_no_old(rec2);
				new_heap_no = rec_get_heap_no_old(rec1);
				ut_ad(!memcmp(rec1, rec2,
					      rec_get_data_size_old(rec2)));

				rec1 = page_rec_get_next_low(rec1, FALSE);
				rec2 = page_rec_get_next_low(rec2, FALSE);
			}

			/* Clear the bit in old_lock. */
			if (old_heap_no < lock->un_member.rec_lock.n_bits
			    && lock_rec_reset_nth_bit(lock, old_heap_no)) {
				/* NOTE that the old lock bitmap could be too
				small for the new heap number! */

				lock_rec_add_to_queue(
					lock->type_mode, block, new_heap_no,
					lock->index, lock->trx, FALSE);
			}

			if (new_heap_no == PAGE_HEAP_NO_SUPREMUM) {
				ut_ad(old_heap_no == PAGE_HEAP_NO_SUPREMUM);
				break;
			}
		}

#ifdef UNIV_DEBUG
		{
			ulint	i = lock_rec_find_set_bit(lock);

			/* Check that all locks were moved. */
			if (i != ULINT_UNDEFINED) {
				ib::fatal() << "lock_move_reorganize_page(): "
					<< i << " not moved in "
					<< (void*) lock;
			}
		}
#endif /* UNIV_DEBUG */
	}

	lock_mutex_exit();

	mem_heap_free(heap);

#ifdef UNIV_DEBUG_LOCK_VALIDATE
	ut_ad(lock_rec_validate_page(block));
#endif
}

/*************************************************************//**
Moves the explicit locks on user records to another page if a record
list end is moved to another page. */
void
lock_move_rec_list_end(
/*===================*/
	const buf_block_t*	new_block,	/*!< in: index page to move to */
	const buf_block_t*	block,		/*!< in: index page */
	const rec_t*		rec)		/*!< in: record on page: this
						is the first record moved */
{
	lock_t*		lock;
	const ulint	comp	= page_rec_is_comp(rec);

	ut_ad(buf_block_get_frame(block) == page_align(rec));
	ut_ad(comp == page_is_comp(buf_block_get_frame(new_block)));

	lock_mutex_enter();

	/* Note: when we move locks from record to record, waiting locks
	and possible granted gap type locks behind them are enqueued in
	the original order, because new elements are inserted to a hash
	table to the end of the hash chain, and lock_rec_add_to_queue
	does not reuse locks if there are waiters in the queue. */

	for (lock = lock_rec_get_first_on_page(lock_sys->rec_hash, block); lock;
	     lock = lock_rec_get_next_on_page(lock)) {
		const rec_t*	rec1	= rec;
		const rec_t*	rec2;
		const ulint	type_mode = lock->type_mode;

		if (comp) {
			if (page_offset(rec1) == PAGE_NEW_INFIMUM) {
				rec1 = page_rec_get_next_low(rec1, TRUE);
			}

			rec2 = page_rec_get_next_low(
				buf_block_get_frame(new_block)
				+ PAGE_NEW_INFIMUM, TRUE);
		} else {
			if (page_offset(rec1) == PAGE_OLD_INFIMUM) {
				rec1 = page_rec_get_next_low(rec1, FALSE);
			}

			rec2 = page_rec_get_next_low(
				buf_block_get_frame(new_block)
				+ PAGE_OLD_INFIMUM, FALSE);
		}

		/* Copy lock requests on user records to new page and
		reset the lock bits on the old */

		for (;;) {
			ulint	rec1_heap_no;
			ulint	rec2_heap_no;

			if (comp) {
				rec1_heap_no = rec_get_heap_no_new(rec1);

				if (rec1_heap_no == PAGE_HEAP_NO_SUPREMUM) {
					break;
				}

				rec2_heap_no = rec_get_heap_no_new(rec2);
				rec1 = page_rec_get_next_low(rec1, TRUE);
				rec2 = page_rec_get_next_low(rec2, TRUE);
			} else {
				rec1_heap_no = rec_get_heap_no_old(rec1);

				if (rec1_heap_no == PAGE_HEAP_NO_SUPREMUM) {
					break;
				}

				rec2_heap_no = rec_get_heap_no_old(rec2);

				ut_ad(!memcmp(rec1, rec2,
					      rec_get_data_size_old(rec2)));

				rec1 = page_rec_get_next_low(rec1, FALSE);
				rec2 = page_rec_get_next_low(rec2, FALSE);
			}

			if (rec1_heap_no < lock->un_member.rec_lock.n_bits
			    && lock_rec_reset_nth_bit(lock, rec1_heap_no)) {
				if (type_mode & LOCK_WAIT) {
					lock_reset_lock_and_trx_wait(lock);
				}

				lock_rec_add_to_queue(
					type_mode, new_block, rec2_heap_no,
					lock->index, lock->trx, FALSE);
			}
		}
	}

	lock_mutex_exit();

#ifdef UNIV_DEBUG_LOCK_VALIDATE
	ut_ad(lock_rec_validate_page(block));
	ut_ad(lock_rec_validate_page(new_block));
#endif
}

/*************************************************************//**
Moves the explicit locks on user records to another page if a record
list start is moved to another page. */
void
lock_move_rec_list_start(
/*=====================*/
	const buf_block_t*	new_block,	/*!< in: index page to
						move to */
	const buf_block_t*	block,		/*!< in: index page */
	const rec_t*		rec,		/*!< in: record on page:
						this is the first
						record NOT copied */
	const rec_t*		old_end)	/*!< in: old
						previous-to-last
						record on new_page
						before the records
						were copied */
{
	lock_t*		lock;
	const ulint	comp	= page_rec_is_comp(rec);

	ut_ad(block->frame == page_align(rec));
	ut_ad(new_block->frame == page_align(old_end));
	ut_ad(comp == page_rec_is_comp(old_end));

	lock_mutex_enter();

	for (lock = lock_rec_get_first_on_page(lock_sys->rec_hash, block); lock;
	     lock = lock_rec_get_next_on_page(lock)) {
		const rec_t*	rec1;
		const rec_t*	rec2;
		const ulint	type_mode = lock->type_mode;

		if (comp) {
			rec1 = page_rec_get_next_low(
				buf_block_get_frame(block)
				+ PAGE_NEW_INFIMUM, TRUE);
			rec2 = page_rec_get_next_low(old_end, TRUE);
		} else {
			rec1 = page_rec_get_next_low(
				buf_block_get_frame(block)
				+ PAGE_OLD_INFIMUM, FALSE);
			rec2 = page_rec_get_next_low(old_end, FALSE);
		}

		/* Copy lock requests on user records to new page and
		reset the lock bits on the old */

		while (rec1 != rec) {
			ulint	rec1_heap_no;
			ulint	rec2_heap_no;

			if (comp) {
				rec1_heap_no = rec_get_heap_no_new(rec1);
				rec2_heap_no = rec_get_heap_no_new(rec2);

				rec1 = page_rec_get_next_low(rec1, TRUE);
				rec2 = page_rec_get_next_low(rec2, TRUE);
			} else {
				rec1_heap_no = rec_get_heap_no_old(rec1);
				rec2_heap_no = rec_get_heap_no_old(rec2);

				ut_ad(!memcmp(rec1, rec2,
					      rec_get_data_size_old(rec2)));

				rec1 = page_rec_get_next_low(rec1, FALSE);
				rec2 = page_rec_get_next_low(rec2, FALSE);
			}

			if (rec1_heap_no < lock->un_member.rec_lock.n_bits
			    && lock_rec_reset_nth_bit(lock, rec1_heap_no)) {
				if (type_mode & LOCK_WAIT) {
					lock_reset_lock_and_trx_wait(lock);
				}

				lock_rec_add_to_queue(
					type_mode, new_block, rec2_heap_no,
					lock->index, lock->trx, FALSE);
			}
		}

#ifdef UNIV_DEBUG
		if (page_rec_is_supremum(rec)) {
			ulint	i;

			for (i = PAGE_HEAP_NO_USER_LOW;
			     i < lock_rec_get_n_bits(lock); i++) {
				if (lock_rec_get_nth_bit(lock, i)) {
					ib::fatal()
						<< "lock_move_rec_list_start():"
						<< i << " not moved in "
						<<  (void*) lock;
				}
			}
		}
#endif /* UNIV_DEBUG */
	}

	lock_mutex_exit();

#ifdef UNIV_DEBUG_LOCK_VALIDATE
	ut_ad(lock_rec_validate_page(block));
#endif
}

/*************************************************************//**
Moves the explicit locks on user records to another page if a record
list start is moved to another page. */
void
lock_rtr_move_rec_list(
/*===================*/
	const buf_block_t*	new_block,	/*!< in: index page to
						move to */
	const buf_block_t*	block,		/*!< in: index page */
	rtr_rec_move_t*		rec_move,       /*!< in: recording records
						moved */
	ulint			num_move)       /*!< in: num of rec to move */
{
	lock_t*		lock;
	ulint		comp;

	if (!num_move) {
		return;
	}

	comp = page_rec_is_comp(rec_move[0].old_rec);

	ut_ad(block->frame == page_align(rec_move[0].old_rec));
	ut_ad(new_block->frame == page_align(rec_move[0].new_rec));
	ut_ad(comp == page_rec_is_comp(rec_move[0].new_rec));

	lock_mutex_enter();

	for (lock = lock_rec_get_first_on_page(lock_sys->rec_hash, block); lock;
	     lock = lock_rec_get_next_on_page(lock)) {
		ulint		moved = 0;
		const rec_t*	rec1;
		const rec_t*	rec2;
		const ulint	type_mode = lock->type_mode;

		/* Copy lock requests on user records to new page and
		reset the lock bits on the old */

		while (moved < num_move) {
			ulint	rec1_heap_no;
			ulint	rec2_heap_no;

			rec1 = rec_move[moved].old_rec;
			rec2 = rec_move[moved].new_rec;

			if (comp) {
				rec1_heap_no = rec_get_heap_no_new(rec1);
				rec2_heap_no = rec_get_heap_no_new(rec2);

			} else {
				rec1_heap_no = rec_get_heap_no_old(rec1);
				rec2_heap_no = rec_get_heap_no_old(rec2);

				ut_ad(!memcmp(rec1, rec2,
					      rec_get_data_size_old(rec2)));
			}

			if (rec1_heap_no < lock->un_member.rec_lock.n_bits
			    && lock_rec_reset_nth_bit(lock, rec1_heap_no)) {
				if (type_mode & LOCK_WAIT) {
					lock_reset_lock_and_trx_wait(lock);
				}

				lock_rec_add_to_queue(
					type_mode, new_block, rec2_heap_no,
					lock->index, lock->trx, FALSE);

				rec_move[moved].moved = true;
			}

			moved++;
		}
	}

	lock_mutex_exit();

#ifdef UNIV_DEBUG_LOCK_VALIDATE
	ut_ad(lock_rec_validate_page(block));
#endif
}
/*************************************************************//**
Updates the lock table when a page is split to the right. */
void
lock_update_split_right(
/*====================*/
	const buf_block_t*	right_block,	/*!< in: right page */
	const buf_block_t*	left_block)	/*!< in: left page */
{
	ulint	heap_no = lock_get_min_heap_no(right_block);

	lock_mutex_enter();

	/* Move the locks on the supremum of the left page to the supremum
	of the right page */

	lock_rec_move(right_block, left_block,
		      PAGE_HEAP_NO_SUPREMUM, PAGE_HEAP_NO_SUPREMUM);

	/* Inherit the locks to the supremum of left page from the successor
	of the infimum on right page */

	lock_rec_inherit_to_gap(left_block, right_block,
				PAGE_HEAP_NO_SUPREMUM, heap_no);

	lock_mutex_exit();
}

/*************************************************************//**
Updates the lock table when a page is merged to the right. */
void
lock_update_merge_right(
/*====================*/
	const buf_block_t*	right_block,	/*!< in: right page to
						which merged */
	const rec_t*		orig_succ,	/*!< in: original
						successor of infimum
						on the right page
						before merge */
	const buf_block_t*	left_block)	/*!< in: merged index
						page which will be
						discarded */
{
	lock_mutex_enter();

	/* Inherit the locks from the supremum of the left page to the
	original successor of infimum on the right page, to which the left
	page was merged */

	lock_rec_inherit_to_gap(right_block, left_block,
				page_rec_get_heap_no(orig_succ),
				PAGE_HEAP_NO_SUPREMUM);

	/* Reset the locks on the supremum of the left page, releasing
	waiting transactions */

	lock_rec_reset_and_release_wait_low(
		lock_sys->rec_hash, left_block, PAGE_HEAP_NO_SUPREMUM);

#ifdef UNIV_DEBUG
	/* there should exist no page lock on the left page,
	otherwise, it will be blocked from merge */
	ulint	space = left_block->page.id.space();
	ulint	page_no = left_block->page.id.page_no();
	ut_ad(lock_rec_get_first_on_page_addr(
			lock_sys->prdt_page_hash, space, page_no) == NULL);
#endif /* UNIV_DEBUG */

	lock_rec_free_all_from_discard_page(left_block);

	lock_mutex_exit();

}

/*************************************************************//**
Updates the lock table when the root page is copied to another in
btr_root_raise_and_insert. Note that we leave lock structs on the
root page, even though they do not make sense on other than leaf
pages: the reason is that in a pessimistic update the infimum record
of the root page will act as a dummy carrier of the locks of the record
to be updated. */
void
lock_update_root_raise(
/*===================*/
	const buf_block_t*	block,	/*!< in: index page to which copied */
	const buf_block_t*	root)	/*!< in: root page */
{
	lock_mutex_enter();

	/* Move the locks on the supremum of the root to the supremum
	of block */

	lock_rec_move(block, root,
		      PAGE_HEAP_NO_SUPREMUM, PAGE_HEAP_NO_SUPREMUM);
	lock_mutex_exit();
}

/*************************************************************//**
Updates the lock table when a page is copied to another and the original page
is removed from the chain of leaf pages, except if page is the root! */
void
lock_update_copy_and_discard(
/*=========================*/
	const buf_block_t*	new_block,	/*!< in: index page to
						which copied */
	const buf_block_t*	block)		/*!< in: index page;
						NOT the root! */
{
	lock_mutex_enter();

	/* Move the locks on the supremum of the old page to the supremum
	of new_page */

	lock_rec_move(new_block, block,
		      PAGE_HEAP_NO_SUPREMUM, PAGE_HEAP_NO_SUPREMUM);
	lock_rec_free_all_from_discard_page(block);

	lock_mutex_exit();
}

/*************************************************************//**
Updates the lock table when a page is split to the left. */
void
lock_update_split_left(
/*===================*/
	const buf_block_t*	right_block,	/*!< in: right page */
	const buf_block_t*	left_block)	/*!< in: left page */
{
	ulint	heap_no = lock_get_min_heap_no(right_block);

	lock_mutex_enter();

	/* Inherit the locks to the supremum of the left page from the
	successor of the infimum on the right page */

	lock_rec_inherit_to_gap(left_block, right_block,
				PAGE_HEAP_NO_SUPREMUM, heap_no);

	lock_mutex_exit();
}

/*************************************************************//**
Updates the lock table when a page is merged to the left. */
void
lock_update_merge_left(
/*===================*/
	const buf_block_t*	left_block,	/*!< in: left page to
						which merged */
	const rec_t*		orig_pred,	/*!< in: original predecessor
						of supremum on the left page
						before merge */
	const buf_block_t*	right_block)	/*!< in: merged index page
						which will be discarded */
{
	const rec_t*	left_next_rec;

	ut_ad(left_block->frame == page_align(orig_pred));

	lock_mutex_enter();

	left_next_rec = page_rec_get_next_const(orig_pred);

	if (!page_rec_is_supremum(left_next_rec)) {

		/* Inherit the locks on the supremum of the left page to the
		first record which was moved from the right page */

		lock_rec_inherit_to_gap(left_block, left_block,
					page_rec_get_heap_no(left_next_rec),
					PAGE_HEAP_NO_SUPREMUM);

		/* Reset the locks on the supremum of the left page,
		releasing waiting transactions */

		lock_rec_reset_and_release_wait_low(
			lock_sys->rec_hash, left_block, PAGE_HEAP_NO_SUPREMUM);
	}

	/* Move the locks from the supremum of right page to the supremum
	of the left page */

	lock_rec_move(left_block, right_block,
		      PAGE_HEAP_NO_SUPREMUM, PAGE_HEAP_NO_SUPREMUM);

#ifdef UNIV_DEBUG
	/* there should exist no page lock on the right page,
	otherwise, it will be blocked from merge */
	ulint	space = right_block->page.id.space();
	ulint	page_no = right_block->page.id.page_no();
	lock_t*	lock_test = lock_rec_get_first_on_page_addr(
		lock_sys->prdt_page_hash, space, page_no);
	ut_ad(!lock_test);
#endif /* UNIV_DEBUG */

	lock_rec_free_all_from_discard_page(right_block);

	lock_mutex_exit();
}

/*************************************************************//**
Resets the original locks on heir and replaces them with gap type locks
inherited from rec. */
void
lock_rec_reset_and_inherit_gap_locks(
/*=================================*/
	const buf_block_t*	heir_block,	/*!< in: block containing the
						record which inherits */
	const buf_block_t*	block,		/*!< in: block containing the
						record from which inherited;
						does NOT reset the locks on
						this record */
	ulint			heir_heap_no,	/*!< in: heap_no of the
						inheriting record */
	ulint			heap_no)	/*!< in: heap_no of the
						donating record */
{
	lock_mutex_enter();

	lock_rec_reset_and_release_wait(heir_block, heir_heap_no);

	lock_rec_inherit_to_gap(heir_block, block, heir_heap_no, heap_no);

	lock_mutex_exit();
}

/*************************************************************//**
Updates the lock table when a page is discarded. */
void
lock_update_discard(
/*================*/
	const buf_block_t*	heir_block,	/*!< in: index page
						which will inherit the locks */
	ulint			heir_heap_no,	/*!< in: heap_no of the record
						which will inherit the locks */
	const buf_block_t*	block)		/*!< in: index page
						which will be discarded */
{
	const rec_t*	rec;
	ulint		heap_no;
	const page_t*	page = block->frame;

	lock_mutex_enter();

	if (!lock_rec_get_first_on_page(lock_sys->rec_hash, block)
	    && (!lock_rec_get_first_on_page(lock_sys->prdt_hash, block))) {
		/* No locks exist on page, nothing to do */

		lock_mutex_exit();

		return;
	}

	/* Inherit all the locks on the page to the record and reset all
	the locks on the page */

	if (page_is_comp(page)) {
		rec = page + PAGE_NEW_INFIMUM;

		do {
			heap_no = rec_get_heap_no_new(rec);

			lock_rec_inherit_to_gap(heir_block, block,
						heir_heap_no, heap_no);

			lock_rec_reset_and_release_wait(block, heap_no);

			rec = page + rec_get_next_offs(rec, TRUE);
		} while (heap_no != PAGE_HEAP_NO_SUPREMUM);
	} else {
		rec = page + PAGE_OLD_INFIMUM;

		do {
			heap_no = rec_get_heap_no_old(rec);

			lock_rec_inherit_to_gap(heir_block, block,
						heir_heap_no, heap_no);

			lock_rec_reset_and_release_wait(block, heap_no);

			rec = page + rec_get_next_offs(rec, FALSE);
		} while (heap_no != PAGE_HEAP_NO_SUPREMUM);
	}

	lock_rec_free_all_from_discard_page(block);

	lock_mutex_exit();
}

/*************************************************************//**
Updates the lock table when a new user record is inserted. */
void
lock_update_insert(
/*===============*/
	const buf_block_t*	block,	/*!< in: buffer block containing rec */
	const rec_t*		rec)	/*!< in: the inserted record */
{
	ulint	receiver_heap_no;
	ulint	donator_heap_no;

	ut_ad(block->frame == page_align(rec));

	/* Inherit the gap-locking locks for rec, in gap mode, from the next
	record */

	if (page_rec_is_comp(rec)) {
		receiver_heap_no = rec_get_heap_no_new(rec);
		donator_heap_no = rec_get_heap_no_new(
			page_rec_get_next_low(rec, TRUE));
	} else {
		receiver_heap_no = rec_get_heap_no_old(rec);
		donator_heap_no = rec_get_heap_no_old(
			page_rec_get_next_low(rec, FALSE));
	}

	lock_rec_inherit_to_gap_if_gap_lock(
		block, receiver_heap_no, donator_heap_no);
}

/*************************************************************//**
Updates the lock table when a record is removed. */
void
lock_update_delete(
/*===============*/
	const buf_block_t*	block,	/*!< in: buffer block containing rec */
	const rec_t*		rec)	/*!< in: the record to be removed */
{
	const page_t*	page = block->frame;
	ulint		heap_no;
	ulint		next_heap_no;

	ut_ad(page == page_align(rec));

	if (page_is_comp(page)) {
		heap_no = rec_get_heap_no_new(rec);
		next_heap_no = rec_get_heap_no_new(page
						   + rec_get_next_offs(rec,
								       TRUE));
	} else {
		heap_no = rec_get_heap_no_old(rec);
		next_heap_no = rec_get_heap_no_old(page
						   + rec_get_next_offs(rec,
								       FALSE));
	}

	lock_mutex_enter();

	/* Let the next record inherit the locks from rec, in gap mode */

	lock_rec_inherit_to_gap(block, block, next_heap_no, heap_no);

	/* Reset the lock bits on rec and release waiting transactions */

	lock_rec_reset_and_release_wait(block, heap_no);

	lock_mutex_exit();
}

/*********************************************************************//**
Stores on the page infimum record the explicit locks of another record.
This function is used to store the lock state of a record when it is
updated and the size of the record changes in the update. The record
is moved in such an update, perhaps to another page. The infimum record
acts as a dummy carrier record, taking care of lock releases while the
actual record is being moved. */
void
lock_rec_store_on_page_infimum(
/*===========================*/
	const buf_block_t*	block,	/*!< in: buffer block containing rec */
	const rec_t*		rec)	/*!< in: record whose lock state
					is stored on the infimum
					record of the same page; lock
					bits are reset on the
					record */
{
	ulint	heap_no = page_rec_get_heap_no(rec);

	ut_ad(block->frame == page_align(rec));

	lock_mutex_enter();

	lock_rec_move(block, block, PAGE_HEAP_NO_INFIMUM, heap_no);

	lock_mutex_exit();
}

/*********************************************************************//**
Restores the state of explicit lock requests on a single record, where the
state was stored on the infimum of the page. */
void
lock_rec_restore_from_page_infimum(
/*===============================*/
	const buf_block_t*	block,	/*!< in: buffer block containing rec */
	const rec_t*		rec,	/*!< in: record whose lock state
					is restored */
	const buf_block_t*	donator)/*!< in: page (rec is not
					necessarily on this page)
					whose infimum stored the lock
					state; lock bits are reset on
					the infimum */
{
	ulint	heap_no = page_rec_get_heap_no(rec);

	lock_mutex_enter();

	lock_rec_move(block, donator, heap_no, PAGE_HEAP_NO_INFIMUM);

	lock_mutex_exit();
}

/*========================= TABLE LOCKS ==============================*/

/** Functor for accessing the embedded node within a table lock. */
struct TableLockGetNode {
	ut_list_node<lock_t>& operator() (lock_t& elem)
	{
		return(elem.un_member.tab_lock.locks);
	}
};

/*********************************************************************//**
Creates a table lock object and adds it as the last in the lock queue
of the table. Does NOT check for deadlocks or lock compatibility.
@return own: new lock object */
UNIV_INLINE
lock_t*
lock_table_create(
/*==============*/
	dict_table_t*	table,	/*!< in/out: database table
				in dictionary cache */
	ulint		type_mode,/*!< in: lock mode possibly ORed with
				LOCK_WAIT */
	trx_t*		trx)	/*!< in: trx */
{
	lock_t*		lock;

	ut_ad(table && trx);
	ut_ad(lock_mutex_own());
	ut_ad(trx_mutex_own(trx));

	check_trx_state(trx);

	if ((type_mode & LOCK_MODE_MASK) == LOCK_AUTO_INC) {
		++table->n_waiting_or_granted_auto_inc_locks;
	}

	/* For AUTOINC locking we reuse the lock instance only if
	there is no wait involved else we allocate the waiting lock
	from the transaction lock heap. */
	if (type_mode == LOCK_AUTO_INC) {

		lock = table->autoinc_lock;

		table->autoinc_trx = trx;

		ib_vector_push(trx->autoinc_locks, &lock);

	} else if (trx->lock.table_cached < trx->lock.table_pool.size()) {
		lock = trx->lock.table_pool[trx->lock.table_cached++];
	} else {

		lock = static_cast<lock_t*>(
			mem_heap_alloc(trx->lock.lock_heap, sizeof(*lock)));

	}

	lock->type_mode = ib_uint32_t(type_mode | LOCK_TABLE);
	lock->trx = trx;

	lock->un_member.tab_lock.table = table;

	ut_ad(table->n_ref_count > 0 || !table->can_be_evicted);

	UT_LIST_ADD_LAST(trx->lock.trx_locks, lock);

	ut_list_append(table->locks, lock, TableLockGetNode());

	if (type_mode & LOCK_WAIT) {

		lock_set_lock_and_trx_wait(lock, trx);
	}

	lock->trx->lock.table_locks.push_back(lock);

	MONITOR_INC(MONITOR_TABLELOCK_CREATED);
	MONITOR_INC(MONITOR_NUM_TABLELOCK);

	return(lock);
}

/*************************************************************//**
Pops autoinc lock requests from the transaction's autoinc_locks. We
handle the case where there are gaps in the array and they need to
be popped off the stack. */
UNIV_INLINE
void
lock_table_pop_autoinc_locks(
/*=========================*/
	trx_t*	trx)	/*!< in/out: transaction that owns the AUTOINC locks */
{
	ut_ad(lock_mutex_own());
	ut_ad(!ib_vector_is_empty(trx->autoinc_locks));

	/* Skip any gaps, gaps are NULL lock entries in the
	trx->autoinc_locks vector. */

	do {
		ib_vector_pop(trx->autoinc_locks);

		if (ib_vector_is_empty(trx->autoinc_locks)) {
			return;
		}

	} while (*(lock_t**) ib_vector_get_last(trx->autoinc_locks) == NULL);
}

/*************************************************************//**
Removes an autoinc lock request from the transaction's autoinc_locks. */
UNIV_INLINE
void
lock_table_remove_autoinc_lock(
/*===========================*/
	lock_t*	lock,	/*!< in: table lock */
	trx_t*	trx)	/*!< in/out: transaction that owns the lock */
{
	lock_t*	autoinc_lock;
	lint	i = ib_vector_size(trx->autoinc_locks) - 1;

	ut_ad(lock_mutex_own());
	ut_ad(lock_get_mode(lock) == LOCK_AUTO_INC);
	ut_ad(lock_get_type_low(lock) & LOCK_TABLE);
	ut_ad(!ib_vector_is_empty(trx->autoinc_locks));

	/* With stored functions and procedures the user may drop
	a table within the same "statement". This special case has
	to be handled by deleting only those AUTOINC locks that were
	held by the table being dropped. */

	autoinc_lock = *static_cast<lock_t**>(
		ib_vector_get(trx->autoinc_locks, i));

	/* This is the default fast case. */

	if (autoinc_lock == lock) {
		lock_table_pop_autoinc_locks(trx);
	} else {
		/* The last element should never be NULL */
		ut_a(autoinc_lock != NULL);

		/* Handle freeing the locks from within the stack. */

		while (--i >= 0) {
			autoinc_lock = *static_cast<lock_t**>(
				ib_vector_get(trx->autoinc_locks, i));

			if (autoinc_lock == lock) {
				void*	null_var = NULL;
				ib_vector_set(trx->autoinc_locks, i, &null_var);
				return;
			}
		}

		/* Must find the autoinc lock. */
		ut_error;
	}
}

/*************************************************************//**
Removes a table lock request from the queue and the trx list of locks;
this is a low-level function which does NOT check if waiting requests
can now be granted. */
UNIV_INLINE
void
lock_table_remove_low(
/*==================*/
	lock_t*	lock)	/*!< in/out: table lock */
{
	trx_t*		trx;
	dict_table_t*	table;

	ut_ad(lock_mutex_own());

	trx = lock->trx;
	table = lock->un_member.tab_lock.table;

	/* Remove the table from the transaction's AUTOINC vector, if
	the lock that is being released is an AUTOINC lock. */
	if (lock_get_mode(lock) == LOCK_AUTO_INC) {

		/* The table's AUTOINC lock can get transferred to
		another transaction before we get here. */
		if (table->autoinc_trx == trx) {
			table->autoinc_trx = NULL;
		}

		/* The locks must be freed in the reverse order from
		the one in which they were acquired. This is to avoid
		traversing the AUTOINC lock vector unnecessarily.

		We only store locks that were granted in the
		trx->autoinc_locks vector (see lock_table_create()
		and lock_grant()). Therefore it can be empty and we
		need to check for that. */

		if (!lock_get_wait(lock)
		    && !ib_vector_is_empty(trx->autoinc_locks)) {

			lock_table_remove_autoinc_lock(lock, trx);
		}

		ut_a(table->n_waiting_or_granted_auto_inc_locks > 0);
		table->n_waiting_or_granted_auto_inc_locks--;
	}

	UT_LIST_REMOVE(trx->lock.trx_locks, lock);
	ut_list_remove(table->locks, lock, TableLockGetNode());

	MONITOR_INC(MONITOR_TABLELOCK_REMOVED);
	MONITOR_DEC(MONITOR_NUM_TABLELOCK);
}

/*********************************************************************//**
Enqueues a waiting request for a table lock which cannot be granted
immediately. Checks for deadlocks.
@return DB_LOCK_WAIT, DB_DEADLOCK, or DB_QUE_THR_SUSPENDED, or
DB_SUCCESS; DB_SUCCESS means that there was a deadlock, but another
transaction was chosen as a victim, and we got the lock immediately:
no need to wait then */
static
dberr_t
lock_table_enqueue_waiting(
/*=======================*/
	ulint		mode,	/*!< in: lock mode this transaction is
				requesting */
	dict_table_t*	table,	/*!< in/out: table */
	que_thr_t*	thr)	/*!< in: query thread */
{
	trx_t*		trx;
	lock_t*		lock;

	ut_ad(lock_mutex_own());
	ut_ad(!srv_read_only_mode);

	trx = thr_get_trx(thr);
	ut_ad(trx_mutex_own(trx));

	/* Test if there already is some other reason to suspend thread:
	we do not enqueue a lock request if the query thread should be
	stopped anyway */

	if (que_thr_stop(thr)) {
		ut_error;

		return(DB_QUE_THR_SUSPENDED);
	}

	switch (trx_get_dict_operation(trx)) {
	case TRX_DICT_OP_NONE:
		break;
	case TRX_DICT_OP_TABLE:
	case TRX_DICT_OP_INDEX:
		ib::error() << "A table lock wait happens in a dictionary"
			" operation. Table " << table->name
			<< ". " << BUG_REPORT_MSG;
		ut_ad(0);
	}

	/* Enqueue the lock request that will wait to be granted */

	lock = lock_table_create(table, mode | LOCK_WAIT, trx);

	/* Release the mutex to obey the latching order.
	This is safe, because DeadlockChecker::check_and_resolve()
	is invoked when a lock wait is enqueued for the currently
	running transaction. Because trx is a running transaction
	(it is not currently suspended because of a lock wait),
	its state can only be changed by this thread, which is
	currently associated with the transaction. */

	trx_mutex_exit(trx);

	const trx_t*	victim_trx;

	victim_trx = DeadlockChecker::check_and_resolve(lock, trx);

	trx_mutex_enter(trx);

	if (victim_trx != 0) {
		ut_ad(victim_trx == trx);

		/* The order here is important, we don't want to
		lose the state of the lock before calling remove. */
		lock_table_remove_low(lock);
		lock_reset_lock_and_trx_wait(lock);

		return(DB_DEADLOCK);

	} else if (trx->lock.wait_lock == NULL) {
		/* Deadlock resolution chose another transaction as a victim,
		and we accidentally got our lock granted! */

		return(DB_SUCCESS);
	}

	trx->lock.que_state = TRX_QUE_LOCK_WAIT;

	trx->lock.wait_started = ut_time();
	trx->lock.was_chosen_as_deadlock_victim = false;

	ut_a(que_thr_stop(thr));

	MONITOR_INC(MONITOR_TABLELOCK_WAIT);

	return(DB_LOCK_WAIT);
}

/*********************************************************************//**
Checks if other transactions have an incompatible mode lock request in
the lock queue.
@return lock or NULL */
UNIV_INLINE
const lock_t*
lock_table_other_has_incompatible(
/*==============================*/
	const trx_t*		trx,	/*!< in: transaction, or NULL if all
					transactions should be included */
	ulint			wait,	/*!< in: LOCK_WAIT if also
					waiting locks are taken into
					account, or 0 if not */
	const dict_table_t*	table,	/*!< in: table */
	lock_mode		mode)	/*!< in: lock mode */
{
	const lock_t*	lock;

	ut_ad(lock_mutex_own());

	for (lock = UT_LIST_GET_LAST(table->locks);
	     lock != NULL;
	     lock = UT_LIST_GET_PREV(un_member.tab_lock.locks, lock)) {

		if (lock->trx != trx
		    && !lock_mode_compatible(lock_get_mode(lock), mode)
		    && (wait || !lock_get_wait(lock))) {

			return(lock);
		}
	}

	return(NULL);
}

/*********************************************************************//**
Locks the specified database table in the mode given. If the lock cannot
be granted immediately, the query thread is put to wait.
@return DB_SUCCESS, DB_LOCK_WAIT, DB_DEADLOCK, or DB_QUE_THR_SUSPENDED */
dberr_t
lock_table(
/*=======*/
	ulint		flags,	/*!< in: if BTR_NO_LOCKING_FLAG bit is set,
				does nothing */
	dict_table_t*	table,	/*!< in/out: database table
				in dictionary cache */
	lock_mode	mode,	/*!< in: lock mode */
	que_thr_t*	thr)	/*!< in: query thread */
{
	trx_t*		trx;
	dberr_t		err;
	const lock_t*	wait_for;

	ut_ad(table && thr);

	/* Given limited visibility of temp-table we can avoid
	locking overhead */
	if ((flags & BTR_NO_LOCKING_FLAG)
	    || srv_read_only_mode
	    || dict_table_is_temporary(table)) {

		return(DB_SUCCESS);
	}

	ut_a(flags == 0);

	trx = thr_get_trx(thr);

	/* Look for equal or stronger locks the same trx already
	has on the table. No need to acquire the lock mutex here
	because only this transacton can add/access table locks
	to/from trx_t::table_locks. */

	if (lock_table_has(trx, table, mode)) {

		return(DB_SUCCESS);
	}

	/* Read only transactions can write to temp tables, we don't want
	to promote them to RW transactions. Their updates cannot be visible
	to other transactions. Therefore we can keep them out
	of the read views. */

	if ((mode == LOCK_IX || mode == LOCK_X)
	    && !trx->read_only
	    && trx->rsegs.m_redo.rseg == 0) {

		trx_set_rw_mode(trx);
	}

	lock_mutex_enter();

	/* We have to check if the new lock is compatible with any locks
	other transactions have in the table lock queue. */

	wait_for = lock_table_other_has_incompatible(
		trx, LOCK_WAIT, table, mode);

	trx_mutex_enter(trx);

	/* Another trx has a request on the table in an incompatible
	mode: this trx may have to wait */

	if (wait_for != NULL) {
		err = lock_table_enqueue_waiting(mode | flags, table, thr);
	} else {
		lock_table_create(table, mode | flags, trx);

		ut_a(!flags || mode == LOCK_S || mode == LOCK_X);

		err = DB_SUCCESS;
	}

	lock_mutex_exit();

	trx_mutex_exit(trx);

	return(err);
}

/*********************************************************************//**
Creates a table IX lock object for a resurrected transaction. */
void
lock_table_ix_resurrect(
/*====================*/
	dict_table_t*	table,	/*!< in/out: table */
	trx_t*		trx)	/*!< in/out: transaction */
{
	ut_ad(trx->is_recovered);

	if (lock_table_has(trx, table, LOCK_IX)) {
		return;
	}

	lock_mutex_enter();

	/* We have to check if the new lock is compatible with any locks
	other transactions have in the table lock queue. */

	ut_ad(!lock_table_other_has_incompatible(
		      trx, LOCK_WAIT, table, LOCK_IX));

	trx_mutex_enter(trx);
	lock_table_create(table, LOCK_IX, trx);
	lock_mutex_exit();
	trx_mutex_exit(trx);
}

/*********************************************************************//**
Checks if a waiting table lock request still has to wait in a queue.
@return TRUE if still has to wait */
static
bool
lock_table_has_to_wait_in_queue(
/*============================*/
	const lock_t*	wait_lock)	/*!< in: waiting table lock */
{
	const dict_table_t*	table;
	const lock_t*		lock;

	ut_ad(lock_mutex_own());
	ut_ad(lock_get_wait(wait_lock));

	table = wait_lock->un_member.tab_lock.table;

	for (lock = UT_LIST_GET_FIRST(table->locks);
	     lock != wait_lock;
	     lock = UT_LIST_GET_NEXT(un_member.tab_lock.locks, lock)) {

		if (lock_has_to_wait(wait_lock, lock)) {

			return(true);
		}
	}

	return(false);
}

/*************************************************************//**
Removes a table lock request, waiting or granted, from the queue and grants
locks to other transactions in the queue, if they now are entitled to a
lock. */
static
void
lock_table_dequeue(
/*===============*/
	lock_t*	in_lock)/*!< in/out: table lock object; transactions waiting
			behind will get their lock requests granted, if
			they are now qualified to it */
{
	ut_ad(lock_mutex_own());
	ut_a(lock_get_type_low(in_lock) == LOCK_TABLE);

	lock_t*	lock = UT_LIST_GET_NEXT(un_member.tab_lock.locks, in_lock);

	lock_table_remove_low(in_lock);

	/* Check if waiting locks in the queue can now be granted: grant
	locks if there are no conflicting locks ahead. */

	for (/* No op */;
	     lock != NULL;
	     lock = UT_LIST_GET_NEXT(un_member.tab_lock.locks, lock)) {

		if (lock_get_wait(lock)
		    && !lock_table_has_to_wait_in_queue(lock)) {

			/* Grant the lock */
			ut_ad(in_lock->trx != lock->trx);
			lock_grant(lock);
		}
	}
}

/*=========================== LOCK RELEASE ==============================*/

/*************************************************************//**
Removes a granted record lock of a transaction from the queue and grants
locks to other transactions waiting in the queue if they now are entitled
to a lock. */
void
lock_rec_unlock(
/*============*/
	trx_t*			trx,	/*!< in/out: transaction that has
					set a record lock */
	const buf_block_t*	block,	/*!< in: buffer block containing rec */
	const rec_t*		rec,	/*!< in: record */
	lock_mode		lock_mode)/*!< in: LOCK_S or LOCK_X */
{
	lock_t*		first_lock;
	lock_t*		lock;
	ulint		heap_no;
	const char*	stmt;
	size_t		stmt_len;

	ut_ad(trx);
	ut_ad(rec);
	ut_ad(block->frame == page_align(rec));
	ut_ad(!trx->lock.wait_lock);
	ut_ad(trx_state_eq(trx, TRX_STATE_ACTIVE));

	heap_no = page_rec_get_heap_no(rec);

	lock_mutex_enter();
	trx_mutex_enter(trx);

	first_lock = lock_rec_get_first(lock_sys->rec_hash, block, heap_no);

	/* Find the last lock with the same lock_mode and transaction
	on the record. */

	for (lock = first_lock; lock != NULL;
	     lock = lock_rec_get_next(heap_no, lock)) {
		if (lock->trx == trx && lock_get_mode(lock) == lock_mode) {
			goto released;
		}
	}

	lock_mutex_exit();
	trx_mutex_exit(trx);

	stmt = innobase_get_stmt_unsafe(trx->mysql_thd, &stmt_len);

	{
		ib::error	err;
		err << "Unlock row could not find a " << lock_mode
			<< " mode lock on the record. Current statement: ";
		err.write(stmt, stmt_len);
	}

	return;

released:
	ut_a(!lock_get_wait(lock));
	lock_rec_reset_nth_bit(lock, heap_no);

	/* Check if we can now grant waiting lock requests */

	for (lock = first_lock; lock != NULL;
	     lock = lock_rec_get_next(heap_no, lock)) {
		if (lock_get_wait(lock)
		    && !lock_rec_has_to_wait_in_queue(lock)) {

			/* Grant the lock */
			ut_ad(trx != lock->trx);
			lock_grant(lock);
		}
	}

	lock_mutex_exit();
	trx_mutex_exit(trx);
}

#ifdef UNIV_DEBUG
/*********************************************************************//**
Check if a transaction that has X or IX locks has set the dict_op
code correctly. */
static
void
lock_check_dict_lock(
/*==================*/
	const lock_t*	lock)	/*!< in: lock to check */
{
	if (lock_get_type_low(lock) == LOCK_REC) {

		/* Check if the transcation locked a record
		in a system table in X mode. It should have set
		the dict_op code correctly if it did. */
		if (lock->index->table->id < DICT_HDR_FIRST_ID
		    && lock_get_mode(lock) == LOCK_X) {

			ut_ad(lock_get_mode(lock) != LOCK_IX);
			ut_ad(lock->trx->dict_operation != TRX_DICT_OP_NONE);
		}
	} else {
		ut_ad(lock_get_type_low(lock) & LOCK_TABLE);

		const dict_table_t*	table;

		table = lock->un_member.tab_lock.table;

		/* Check if the transcation locked a system table
		in IX mode. It should have set the dict_op code
		correctly if it did. */
		if (table->id < DICT_HDR_FIRST_ID
		    && (lock_get_mode(lock) == LOCK_X
			|| lock_get_mode(lock) == LOCK_IX)) {

			ut_ad(lock->trx->dict_operation != TRX_DICT_OP_NONE);
		}
	}
}
#endif /* UNIV_DEBUG */

/*********************************************************************//**
Releases transaction locks, and releases possible other transactions waiting
because of these locks. */
static
void
lock_release(
/*=========*/
	trx_t*	trx)	/*!< in/out: transaction */
{
	lock_t*		lock;
	ulint		count = 0;
	trx_id_t	max_trx_id = trx_sys_get_max_trx_id();

	ut_ad(lock_mutex_own());
	ut_ad(!trx_mutex_own(trx));
	ut_ad(!trx->is_dd_trx);

	for (lock = UT_LIST_GET_LAST(trx->lock.trx_locks);
	     lock != NULL;
	     lock = UT_LIST_GET_LAST(trx->lock.trx_locks)) {

		ut_d(lock_check_dict_lock(lock));

		if (lock_get_type_low(lock) == LOCK_REC) {

			lock_rec_dequeue_from_page(lock);
		} else {
			dict_table_t*	table;

			table = lock->un_member.tab_lock.table;

			if (lock_get_mode(lock) != LOCK_IS
			    && trx->undo_no != 0) {

				/* The trx may have modified the table. We
				block the use of the MySQL query cache for
				all currently active transactions. */

				table->query_cache_inv_id = max_trx_id;
			}

			lock_table_dequeue(lock);
		}

		if (count == LOCK_RELEASE_INTERVAL) {
			/* Release the mutex for a while, so that we
			do not monopolize it */

			lock_mutex_exit();

			lock_mutex_enter();

			count = 0;
		}

		++count;
	}
}

/* True if a lock mode is S or X */
#define IS_LOCK_S_OR_X(lock) \
	(lock_get_mode(lock) == LOCK_S \
	 || lock_get_mode(lock) == LOCK_X)

/*********************************************************************//**
Removes table locks of the transaction on a table to be dropped. */
static
void
lock_trx_table_locks_remove(
/*========================*/
	const lock_t*	lock_to_remove)		/*!< in: lock to remove */
{
	trx_t*		trx = lock_to_remove->trx;

	ut_ad(lock_mutex_own());

	/* It is safe to read this because we are holding the lock mutex */
	if (!trx->lock.cancel) {
		trx_mutex_enter(trx);
	} else {
		ut_ad(trx_mutex_own(trx));
	}

	typedef lock_pool_t::reverse_iterator iterator;

	iterator	end = trx->lock.table_locks.rend();

	for (iterator it = trx->lock.table_locks.rbegin(); it != end; ++it) {

		const lock_t*	lock = *it;

		if (lock == NULL) {
			continue;
		}

		ut_a(trx == lock->trx);
		ut_a(lock_get_type_low(lock) & LOCK_TABLE);
		ut_a(lock->un_member.tab_lock.table != NULL);

		if (lock == lock_to_remove) {

			*it = NULL;

			if (!trx->lock.cancel) {
				trx_mutex_exit(trx);
			}

			return;
		}
	}

	if (!trx->lock.cancel) {
		trx_mutex_exit(trx);
	}

	/* Lock must exist in the vector. */
	ut_error;
}

/*********************************************************************//**
Removes locks of a transaction on a table to be dropped.
If remove_also_table_sx_locks is TRUE then table-level S and X locks are
also removed in addition to other table-level and record-level locks.
No lock that is going to be removed is allowed to be a wait lock. */
static
void
lock_remove_all_on_table_for_trx(
/*=============================*/
	dict_table_t*	table,			/*!< in: table to be dropped */
	trx_t*		trx,			/*!< in: a transaction */
	ibool		remove_also_table_sx_locks)/*!< in: also removes
						table S and X locks */
{
	lock_t*		lock;
	lock_t*		prev_lock;

	ut_ad(lock_mutex_own());

	for (lock = UT_LIST_GET_LAST(trx->lock.trx_locks);
	     lock != NULL;
	     lock = prev_lock) {

		prev_lock = UT_LIST_GET_PREV(trx_locks, lock);

		if (lock_get_type_low(lock) == LOCK_REC
		    && lock->index->table == table) {
			ut_a(!lock_get_wait(lock));

			lock_rec_discard(lock);
		} else if (lock_get_type_low(lock) & LOCK_TABLE
			   && lock->un_member.tab_lock.table == table
			   && (remove_also_table_sx_locks
			       || !IS_LOCK_S_OR_X(lock))) {

			ut_a(!lock_get_wait(lock));

			lock_trx_table_locks_remove(lock);
			lock_table_remove_low(lock);
		}
	}
}

/*******************************************************************//**
Remove any explicit record locks held by recovering transactions on
the table.
@return number of recovered transactions examined */
static
ulint
lock_remove_recovered_trx_record_locks(
/*===================================*/
	dict_table_t*	table)	/*!< in: check if there are any locks
				held on records in this table or on the
				table itself */
{
	ut_a(table != NULL);
	ut_ad(lock_mutex_own());

	ulint		n_recovered_trx = 0;

	mutex_enter(&trx_sys->mutex);

	for (trx_t* trx = UT_LIST_GET_FIRST(trx_sys->rw_trx_list);
	     trx != NULL;
	     trx = UT_LIST_GET_NEXT(trx_list, trx)) {

		assert_trx_in_rw_list(trx);

		if (!trx->is_recovered) {
			continue;
		}

		/* Because we are holding the lock_sys->mutex,
		implicit locks cannot be converted to explicit ones
		while we are scanning the explicit locks. */

		lock_t*	next_lock;

		for (lock_t* lock = UT_LIST_GET_FIRST(trx->lock.trx_locks);
		     lock != NULL;
		     lock = next_lock) {

			ut_a(lock->trx == trx);

			/* Recovered transactions can't wait on a lock. */

			ut_a(!lock_get_wait(lock));

			next_lock = UT_LIST_GET_NEXT(trx_locks, lock);

			switch (lock_get_type_low(lock)) {
			default:
				ut_error;
			case LOCK_TABLE:
				if (lock->un_member.tab_lock.table == table) {
					lock_trx_table_locks_remove(lock);
					lock_table_remove_low(lock);
				}
				break;
			case LOCK_REC:
				if (lock->index->table == table) {
					lock_rec_discard(lock);
				}
			}
		}

		++n_recovered_trx;
	}

	mutex_exit(&trx_sys->mutex);

	return(n_recovered_trx);
}

/*********************************************************************//**
Removes locks on a table to be dropped or truncated.
If remove_also_table_sx_locks is TRUE then table-level S and X locks are
also removed in addition to other table-level and record-level locks.
No lock, that is going to be removed, is allowed to be a wait lock. */
void
lock_remove_all_on_table(
/*=====================*/
	dict_table_t*	table,			/*!< in: table to be dropped
						or truncated */
	ibool		remove_also_table_sx_locks)/*!< in: also removes
						table S and X locks */
{
	lock_t*		lock;

	lock_mutex_enter();

	for (lock = UT_LIST_GET_FIRST(table->locks);
	     lock != NULL;
	     /* No op */) {

		lock_t*	prev_lock;

		prev_lock = UT_LIST_GET_PREV(un_member.tab_lock.locks, lock);

		/* If we should remove all locks (remove_also_table_sx_locks
		is TRUE), or if the lock is not table-level S or X lock,
		then check we are not going to remove a wait lock. */
		if (remove_also_table_sx_locks
		    || !(lock_get_type(lock) == LOCK_TABLE
			 && IS_LOCK_S_OR_X(lock))) {

			ut_a(!lock_get_wait(lock));
		}

		lock_remove_all_on_table_for_trx(
			table, lock->trx, remove_also_table_sx_locks);

		if (prev_lock == NULL) {
			if (lock == UT_LIST_GET_FIRST(table->locks)) {
				/* lock was not removed, pick its successor */
				lock = UT_LIST_GET_NEXT(
					un_member.tab_lock.locks, lock);
			} else {
				/* lock was removed, pick the first one */
				lock = UT_LIST_GET_FIRST(table->locks);
			}
		} else if (UT_LIST_GET_NEXT(un_member.tab_lock.locks,
					    prev_lock) != lock) {
			/* If lock was removed by
			lock_remove_all_on_table_for_trx() then pick the
			successor of prev_lock ... */
			lock = UT_LIST_GET_NEXT(
				un_member.tab_lock.locks, prev_lock);
		} else {
			/* ... otherwise pick the successor of lock. */
			lock = UT_LIST_GET_NEXT(
				un_member.tab_lock.locks, lock);
		}
	}

	/* Note: Recovered transactions don't have table level IX or IS locks
	but can have implicit record locks that have been converted to explicit
	record locks. Such record locks cannot be freed by traversing the
	transaction lock list in dict_table_t (as above). */

	if (!lock_sys->rollback_complete
	    && lock_remove_recovered_trx_record_locks(table) == 0) {

		lock_sys->rollback_complete = TRUE;
	}

	lock_mutex_exit();
}

/*===================== VALIDATION AND DEBUGGING ====================*/

/*********************************************************************//**
Prints info of a table lock. */
void
lock_table_print(
/*=============*/
	FILE*		file,	/*!< in: file where to print */
	const lock_t*	lock)	/*!< in: table type lock */
{
	ut_ad(lock_mutex_own());
	ut_a(lock_get_type_low(lock) == LOCK_TABLE);

	fputs("TABLE LOCK table ", file);
	ut_print_name(file, lock->trx,
		      lock->un_member.tab_lock.table->name.m_name);
	fprintf(file, " trx id " TRX_ID_FMT, trx_get_id_for_print(lock->trx));

	if (lock_get_mode(lock) == LOCK_S) {
		fputs(" lock mode S", file);
	} else if (lock_get_mode(lock) == LOCK_X) {
		ut_ad(lock->trx->id != 0);
		fputs(" lock mode X", file);
	} else if (lock_get_mode(lock) == LOCK_IS) {
		fputs(" lock mode IS", file);
	} else if (lock_get_mode(lock) == LOCK_IX) {
		ut_ad(lock->trx->id != 0);
		fputs(" lock mode IX", file);
	} else if (lock_get_mode(lock) == LOCK_AUTO_INC) {
		fputs(" lock mode AUTO-INC", file);
	} else {
		fprintf(file, " unknown lock mode %lu",
			(ulong) lock_get_mode(lock));
	}

	if (lock_get_wait(lock)) {
		fputs(" waiting", file);
	}

	putc('\n', file);
}

/*********************************************************************//**
Prints info of a record lock. */
void
lock_rec_print(
/*===========*/
	FILE*		file,	/*!< in: file where to print */
	const lock_t*	lock)	/*!< in: record type lock */
{
	ulint			space;
	ulint			page_no;
	mtr_t			mtr;
	mem_heap_t*		heap		= NULL;
	ulint			offsets_[REC_OFFS_NORMAL_SIZE];
	ulint*			offsets		= offsets_;
	rec_offs_init(offsets_);

	ut_ad(lock_mutex_own());
	ut_a(lock_get_type_low(lock) == LOCK_REC);

	space = lock->un_member.rec_lock.space;
	page_no = lock->un_member.rec_lock.page_no;

	fprintf(file, "RECORD LOCKS space id %lu page no %lu n bits %lu "
		"index %s of table ",
		(ulong) space, (ulong) page_no,
		(ulong) lock_rec_get_n_bits(lock),
		lock->index->name());
	ut_print_name(file, lock->trx, lock->index->table_name);
	fprintf(file, " trx id " TRX_ID_FMT, trx_get_id_for_print(lock->trx));

	if (lock_get_mode(lock) == LOCK_S) {
		fputs(" lock mode S", file);
	} else if (lock_get_mode(lock) == LOCK_X) {
		fputs(" lock_mode X", file);
	} else {
		ut_error;
	}

	if (lock_rec_get_gap(lock)) {
		fputs(" locks gap before rec", file);
	}

	if (lock_rec_get_rec_not_gap(lock)) {
		fputs(" locks rec but not gap", file);
	}

	if (lock_rec_get_insert_intention(lock)) {
		fputs(" insert intention", file);
	}

	if (lock_get_wait(lock)) {
		fputs(" waiting", file);
	}

	mtr_start(&mtr);

	putc('\n', file);

	const buf_block_t*	block;

	block = buf_page_try_get(page_id_t(space, page_no), &mtr);

	for (ulint i = 0; i < lock_rec_get_n_bits(lock); ++i) {

		if (!lock_rec_get_nth_bit(lock, i)) {
			continue;
		}

		fprintf(file, "Record lock, heap no %lu", (ulong) i);

		if (block) {
			const rec_t*	rec;

			rec = page_find_rec_with_heap_no(
				buf_block_get_frame(block), i);

			offsets = rec_get_offsets(
				rec, lock->index, offsets,
				ULINT_UNDEFINED, &heap);

			putc(' ', file);
			rec_print_new(file, rec, offsets);
		}

		putc('\n', file);
	}

	mtr_commit(&mtr);

	if (heap) {
		mem_heap_free(heap);
	}
}

#ifdef UNIV_DEBUG
/* Print the number of lock structs from lock_print_info_summary() only
in non-production builds for performance reasons, see
http://bugs.mysql.com/36942 */
#define PRINT_NUM_OF_LOCK_STRUCTS
#endif /* UNIV_DEBUG */

#ifdef PRINT_NUM_OF_LOCK_STRUCTS
/*********************************************************************//**
Calculates the number of record lock structs in the record lock hash table.
@return number of record locks */
static
ulint
lock_get_n_rec_locks(void)
/*======================*/
{
	ulint	n_locks	= 0;
	ulint	i;

	ut_ad(lock_mutex_own());

	for (i = 0; i < hash_get_n_cells(lock_sys->rec_hash); i++) {
		const lock_t*	lock;

		for (lock = static_cast<const lock_t*>(
				HASH_GET_FIRST(lock_sys->rec_hash, i));
		     lock != 0;
		     lock = static_cast<const lock_t*>(
				HASH_GET_NEXT(hash, lock))) {

			n_locks++;
		}
	}

	return(n_locks);
}
#endif /* PRINT_NUM_OF_LOCK_STRUCTS */

/*********************************************************************//**
Prints info of locks for all transactions.
@return FALSE if not able to obtain lock mutex
and exits without printing info */
ibool
lock_print_info_summary(
/*====================*/
	FILE*	file,	/*!< in: file where to print */
	ibool	nowait)	/*!< in: whether to wait for the lock mutex */
{
	/* if nowait is FALSE, wait on the lock mutex,
	otherwise return immediately if fail to obtain the
	mutex. */
	if (!nowait) {
		lock_mutex_enter();
	} else if (lock_mutex_enter_nowait()) {
		fputs("FAIL TO OBTAIN LOCK MUTEX,"
		      " SKIP LOCK INFO PRINTING\n", file);
		return(FALSE);
	}

	if (lock_deadlock_found) {
		fputs("------------------------\n"
		      "LATEST DETECTED DEADLOCK\n"
		      "------------------------\n", file);

		if (!srv_read_only_mode) {
			ut_copy_file(file, lock_latest_err_file);
		}
	}

	fputs("------------\n"
	      "TRANSACTIONS\n"
	      "------------\n", file);

	fprintf(file, "Trx id counter " TRX_ID_FMT "\n",
		trx_sys_get_max_trx_id());

	fprintf(file,
		"Purge done for trx's n:o < " TRX_ID_FMT
		" undo n:o < " TRX_ID_FMT " state: ",
		purge_sys->iter.trx_no,
		purge_sys->iter.undo_no);

	/* Note: We are reading the state without the latch. One because it
	will violate the latching order and two because we are merely querying
	the state of the variable for display. */

	switch (purge_sys->state){
	case PURGE_STATE_INIT:
		/* Should never be in this state while the system is running. */
		ut_error;

	case PURGE_STATE_EXIT:
		fprintf(file, "exited");
		break;

	case PURGE_STATE_DISABLED:
		fprintf(file, "disabled");
		break;

	case PURGE_STATE_RUN:
		fprintf(file, "running");
		/* Check if it is waiting for more data to arrive. */
		if (!purge_sys->running) {
			fprintf(file, " but idle");
		}
		break;

	case PURGE_STATE_STOP:
		fprintf(file, "stopped");
		break;
	}

	fprintf(file, "\n");

	fprintf(file,
		"History list length %lu\n",
		(ulong) trx_sys->rseg_history_len);

#ifdef PRINT_NUM_OF_LOCK_STRUCTS
	fprintf(file,
		"Total number of lock structs in row lock hash table %lu\n",
		(ulong) lock_get_n_rec_locks());
#endif /* PRINT_NUM_OF_LOCK_STRUCTS */
	return(TRUE);
}

/** Functor to print not-started transaction from the mysql_trx_list. */

struct	PrintNotStarted {

	PrintNotStarted(FILE* file) : m_file(file) { }

	void	operator()(const trx_t* trx)
	{
		ut_ad(trx->in_mysql_trx_list);
		ut_ad(mutex_own(&trx_sys->mutex));

		/* See state transitions and locking rules in trx0trx.h */

		if (trx_state_eq(trx, TRX_STATE_NOT_STARTED)) {

			fputs("---", m_file);
			trx_print_latched(m_file, trx, 600);
		}
	}

	FILE*		m_file;
};

/** Iterate over a transaction's locks. Keeping track of the
iterator using an ordinal value. */

class TrxLockIterator {
public:
	TrxLockIterator() { rewind(); }

	/** Get the m_index(th) lock of a transaction.
	@return current lock or 0 */
	const lock_t* current(const trx_t* trx) const
	{
		lock_t*	lock;
		ulint	i = 0;

		for (lock = UT_LIST_GET_FIRST(trx->lock.trx_locks);
		     lock != NULL && i < m_index;
		     lock = UT_LIST_GET_NEXT(trx_locks, lock), ++i) {

			/* No op */
		}

		return(lock);
	}

	/** Set the ordinal value to 0 */
	void rewind()
	{
		m_index = 0;
	}

	/** Increment the ordinal value.
	@retun the current index value */
	ulint next()
	{
		return(++m_index);
	}

private:
	/** Current iterator position */
	ulint		m_index;
};

/** This iterates over both the RW and RO trx_sys lists. We need to keep
track where the iterator was up to and we do that using an ordinal value. */

class TrxListIterator {
public:
	TrxListIterator() : m_index()
	{
		/* We iterate over the RW trx list first. */

		m_trx_list = &trx_sys->rw_trx_list;
	}

	/** Get the current transaction whose ordinality is m_index.
	@return current transaction or 0 */

	const trx_t* current()
	{
		return(reposition());
	}

	/** Advance the transaction current ordinal value and reset the
	transaction lock ordinal value */

	void next()
	{
		++m_index;
		m_lock_iter.rewind();
	}

	TrxLockIterator& lock_iter()
	{
		return(m_lock_iter);
	}

private:
	/** Reposition the "cursor" on the current transaction. If it
	is the first time then the "cursor" will be positioned on the
	first transaction.

	@return transaction instance or 0 */
	const trx_t* reposition() const
	{
		ulint	i;
		trx_t*	trx;

		/* Make the transaction at the ordinal value of m_index
		the current transaction. ie. reposition/restore */

		for (i = 0, trx = UT_LIST_GET_FIRST(*m_trx_list);
		     trx != NULL && (i < m_index);
		     trx = UT_LIST_GET_NEXT(trx_list, trx), ++i) {

			check_trx_state(trx);
		}

		return(trx);
	}

	/** Ordinal value of the transaction in the current transaction list */
	ulint			m_index;

	/** Current transaction list */
	trx_ut_list_t*		m_trx_list;

	/** For iterating over a transaction's locks */
	TrxLockIterator		m_lock_iter;
};

/** Prints transaction lock wait and MVCC state.
@param[in,out]	file	file where to print
@param[in]	trx	transaction */
void
lock_trx_print_wait_and_mvcc_state(
	FILE*		file,
	const trx_t*	trx)
{
	fprintf(file, "---");

	trx_print_latched(file, trx, 600);

	const ReadView*	read_view = trx_get_read_view(trx);

	if (read_view != NULL) {
		read_view->print_limits(file);
	}

	if (trx->lock.que_state == TRX_QUE_LOCK_WAIT) {

		fprintf(file,
			"------- TRX HAS BEEN WAITING %lu SEC"
			" FOR THIS LOCK TO BE GRANTED:\n",
			(ulong) difftime(ut_time(), trx->lock.wait_started));

		if (lock_get_type_low(trx->lock.wait_lock) == LOCK_REC) {
			lock_rec_print(file, trx->lock.wait_lock);
		} else {
			lock_table_print(file, trx->lock.wait_lock);
		}

		fprintf(file, "------------------\n");
	}
}

/*********************************************************************//**
Prints info of locks for a transaction. This function will release the
lock mutex and the trx_sys_t::mutex if the page was read from disk.
@return true if page was read from the tablespace */
static
bool
lock_rec_fetch_page(
/*================*/
	const lock_t*	lock)	/*!< in: record lock */
{
	ut_ad(lock_get_type_low(lock) == LOCK_REC);

	ulint			space_id = lock->un_member.rec_lock.space;
	fil_space_t*		space;
	bool			found;
	const page_size_t&	page_size = fil_space_get_page_size(space_id,
								    &found);
	ulint			page_no = lock->un_member.rec_lock.page_no;

	/* Check if the .ibd file exists. */
	if (found) {
		mtr_t	mtr;

		lock_mutex_exit();

		mutex_exit(&trx_sys->mutex);

		DEBUG_SYNC_C("innodb_monitor_before_lock_page_read");

		/* Check if the space is exists or not. only
		when the space is valid, try to get the page. */
		space = fil_space_acquire(space_id);
		if (space) {
			mtr_start(&mtr);
			buf_page_get_gen(
				page_id_t(space_id, page_no), page_size,
				RW_NO_LATCH, NULL,
				BUF_GET_POSSIBLY_FREED,
				__FILE__, __LINE__, &mtr);
			mtr_commit(&mtr);
			fil_space_release(space);
		}

		lock_mutex_enter();

		mutex_enter(&trx_sys->mutex);

		return(true);
	}

	return(false);
}

/*********************************************************************//**
Prints info of locks for a transaction.
@return true if all printed, false if latches were released. */
static
bool
lock_trx_print_locks(
/*=================*/
	FILE*		file,		/*!< in/out: File to write */
	const trx_t*	trx,		/*!< in: current transaction */
	TrxLockIterator&iter,		/*!< in: transaction lock iterator */
	bool		load_block)	/*!< in: if true then read block
					from disk */
{
	const lock_t* lock;

	/* Iterate over the transaction's locks. */
	while ((lock = iter.current(trx)) != 0) {

		if (lock_get_type_low(lock) == LOCK_REC) {

			if (load_block) {

				/* Note: lock_rec_fetch_page() will
				release both the lock mutex and the
				trx_sys_t::mutex if it does a read
				from disk. */

				if (lock_rec_fetch_page(lock)) {
					/* We need to resync the
					current transaction. */
					return(false);
				}

				/* It is a single table tablespace
				and the .ibd file is missing
				(TRUNCATE TABLE probably stole the
				locks): just print the lock without
				attempting to load the page in the
				buffer pool. */

				fprintf(file,
					"RECORD LOCKS on non-existing"
					" space %u\n",
					lock->un_member.rec_lock.space);
			}

			/* Print all the record locks on the page from
			the record lock bitmap */

			lock_rec_print(file, lock);

			load_block = true;

		} else {
			ut_ad(lock_get_type_low(lock) & LOCK_TABLE);

			lock_table_print(file, lock);
		}

		if (iter.next() >= 10) {

			fprintf(file,
				"10 LOCKS PRINTED FOR THIS TRX:"
				" SUPPRESSING FURTHER PRINTS\n");

			break;
		}
	}

	return(true);
}

/*********************************************************************//**
Prints info of locks for each transaction. This function assumes that the
caller holds the lock mutex and more importantly it will release the lock
mutex on behalf of the caller. (This should be fixed in the future). */
void
lock_print_info_all_transactions(
/*=============================*/
	FILE*		file)	/*!< in/out: file where to print */
{
	ut_ad(lock_mutex_own());

	fprintf(file, "LIST OF TRANSACTIONS FOR EACH SESSION:\n");

	mutex_enter(&trx_sys->mutex);

	/* First print info on non-active transactions */

	/* NOTE: information of auto-commit non-locking read-only
	transactions will be omitted here. The information will be
	available from INFORMATION_SCHEMA.INNODB_TRX. */

	PrintNotStarted	print_not_started(file);
	ut_list_map(trx_sys->mysql_trx_list, print_not_started);

	const trx_t*	trx;
	TrxListIterator	trx_iter;
	const trx_t*	prev_trx = 0;

	/* Control whether a block should be fetched from the buffer pool. */
	bool		load_block = true;
	bool		monitor = srv_print_innodb_lock_monitor;

	while ((trx = trx_iter.current()) != 0) {

		check_trx_state(trx);

		if (trx != prev_trx) {
			lock_trx_print_wait_and_mvcc_state(file, trx);
			prev_trx = trx;

			/* The transaction that read in the page is no
			longer the one that read the page in. We need to
			force a page read. */
			load_block = true;
		}

		/* If we need to print the locked record contents then we
		need to fetch the containing block from the buffer pool. */
		if (monitor) {

			/* Print the locks owned by the current transaction. */
			TrxLockIterator& lock_iter = trx_iter.lock_iter();

			if (!lock_trx_print_locks(
					file, trx, lock_iter, load_block)) {

				/* Resync trx_iter, the trx_sys->mutex and
				the lock mutex were released. A page was
				successfully read in.  We need to print its
				contents on the next call to
				lock_trx_print_locks(). On the next call to
				lock_trx_print_locks() we should simply print
				the contents of the page just read in.*/
				load_block = false;

				continue;
			}
		}

		load_block = true;

		/* All record lock details were printed without fetching
		a page from disk, or we didn't need to print the detail. */
		trx_iter.next();
	}

	lock_mutex_exit();
	mutex_exit(&trx_sys->mutex);

	ut_ad(lock_validate());
}

#ifdef UNIV_DEBUG
/*********************************************************************//**
Find the the lock in the trx_t::trx_lock_t::table_locks vector.
@return true if found */
static
bool
lock_trx_table_locks_find(
/*======================*/
	trx_t*		trx,		/*!< in: trx to validate */
	const lock_t*	find_lock)	/*!< in: lock to find */
{
	bool		found = false;

	trx_mutex_enter(trx);

	typedef lock_pool_t::const_reverse_iterator iterator;

	iterator	end = trx->lock.table_locks.rend();

	for (iterator it = trx->lock.table_locks.rbegin(); it != end; ++it) {

		const lock_t*	lock = *it;

		if (lock == NULL) {

			continue;

		} else if (lock == find_lock) {

			/* Can't be duplicates. */
			ut_a(!found);
			found = true;
		}

		ut_a(trx == lock->trx);
		ut_a(lock_get_type_low(lock) & LOCK_TABLE);
		ut_a(lock->un_member.tab_lock.table != NULL);
	}

	trx_mutex_exit(trx);

	return(found);
}

/*********************************************************************//**
Validates the lock queue on a table.
@return TRUE if ok */
static
ibool
lock_table_queue_validate(
/*======================*/
	const dict_table_t*	table)	/*!< in: table */
{
	const lock_t*	lock;

	ut_ad(lock_mutex_own());
	ut_ad(trx_sys_mutex_own());

	for (lock = UT_LIST_GET_FIRST(table->locks);
	     lock != NULL;
	     lock = UT_LIST_GET_NEXT(un_member.tab_lock.locks, lock)) {

		/* lock->trx->state cannot change from or to NOT_STARTED
		while we are holding the trx_sys->mutex. It may change
		from ACTIVE to PREPARED, but it may not change to
		COMMITTED, because we are holding the lock_sys->mutex. */
		ut_ad(trx_assert_started(lock->trx));

		if (!lock_get_wait(lock)) {

			ut_a(!lock_table_other_has_incompatible(
				     lock->trx, 0, table,
				     lock_get_mode(lock)));
		} else {

			ut_a(lock_table_has_to_wait_in_queue(lock));
		}

		ut_a(lock_trx_table_locks_find(lock->trx, lock));
	}

	return(TRUE);
}

/*********************************************************************//**
Validates the lock queue on a single record.
@return TRUE if ok */
static
ibool
lock_rec_queue_validate(
/*====================*/
	ibool			locked_lock_trx_sys,
					/*!< in: if the caller holds
					both the lock mutex and
					trx_sys_t->lock. */
	const buf_block_t*	block,	/*!< in: buffer block containing rec */
	const rec_t*		rec,	/*!< in: record to look at */
	const dict_index_t*	index,	/*!< in: index, or NULL if not known */
	const ulint*		offsets)/*!< in: rec_get_offsets(rec, index) */
{
	const trx_t*	impl_trx;
	const lock_t*	lock;
	ulint		heap_no;

	ut_a(rec);
	ut_a(block->frame == page_align(rec));
	ut_ad(rec_offs_validate(rec, index, offsets));
	ut_ad(!page_rec_is_comp(rec) == !rec_offs_comp(offsets));
	ut_ad(lock_mutex_own() == locked_lock_trx_sys);
	ut_ad(!index || dict_index_is_clust(index)
	      || !dict_index_is_online_ddl(index));

	heap_no = page_rec_get_heap_no(rec);

	if (!locked_lock_trx_sys) {
		lock_mutex_enter();
		mutex_enter(&trx_sys->mutex);
	}

	if (!page_rec_is_user_rec(rec)) {

		for (lock = lock_rec_get_first(lock_sys->rec_hash, block, heap_no);
		     lock != NULL;
		     lock = lock_rec_get_next_const(heap_no, lock)) {

			ut_ad(!trx_is_ac_nl_ro(lock->trx));

			if (lock_get_wait(lock)) {
				ut_a(lock_rec_has_to_wait_in_queue(lock));
			}

			if (index) {
				ut_a(lock->index == index);
			}
		}

		goto func_exit;
	}

	if (!index);
	else if (dict_index_is_clust(index)) {
		trx_id_t	trx_id;

		/* Unlike the non-debug code, this invariant can only succeed
		if the check and assertion are covered by the lock mutex. */

		trx_id = lock_clust_rec_some_has_impl(rec, index, offsets);
		impl_trx = trx_rw_is_active_low(trx_id, NULL);

		ut_ad(lock_mutex_own());
		/* impl_trx cannot be committed until lock_mutex_exit()
		because lock_trx_release_locks() acquires lock_sys->mutex */

		if (impl_trx != NULL
		    && lock_rec_other_has_expl_req(
			    LOCK_S, block, false, heap_no, impl_trx)) {

			ut_a(lock_rec_has_expl(LOCK_X | LOCK_REC_NOT_GAP,
					       block, heap_no, impl_trx));
		}
	}

	for (lock = lock_rec_get_first(lock_sys->rec_hash, block, heap_no);
	     lock != NULL;
	     lock = lock_rec_get_next_const(heap_no, lock)) {

		ut_ad(!trx_is_ac_nl_ro(lock->trx));

		if (index) {
			ut_a(lock->index == index);
		}

		if (!lock_rec_get_gap(lock) && !lock_get_wait(lock)) {

			lock_mode	mode;

			if (lock_get_mode(lock) == LOCK_S) {
				mode = LOCK_X;
			} else {
				mode = LOCK_S;
			}
			ut_a(!lock_rec_other_has_expl_req(
				     mode, block, true, heap_no, lock->trx));

		} else if (lock_get_wait(lock) && !lock_rec_get_gap(lock)) {

			ut_a(lock_rec_has_to_wait_in_queue(lock));
		}
	}

func_exit:
	if (!locked_lock_trx_sys) {
		lock_mutex_exit();
		mutex_exit(&trx_sys->mutex);
	}

	return(TRUE);
}

/*********************************************************************//**
Validates the record lock queues on a page.
@return TRUE if ok */
static
ibool
lock_rec_validate_page(
/*===================*/
	const buf_block_t*	block)	/*!< in: buffer block */
{
	const lock_t*	lock;
	const rec_t*	rec;
	ulint		nth_lock	= 0;
	ulint		nth_bit		= 0;
	ulint		i;
	mem_heap_t*	heap		= NULL;
	ulint		offsets_[REC_OFFS_NORMAL_SIZE];
	ulint*		offsets		= offsets_;
	rec_offs_init(offsets_);

	ut_ad(!lock_mutex_own());

	lock_mutex_enter();
	mutex_enter(&trx_sys->mutex);
loop:
	lock = lock_rec_get_first_on_page_addr(
		lock_sys->rec_hash,
		block->page.id.space(), block->page.id.page_no());

	if (!lock) {
		goto function_exit;
	}

#if defined UNIV_DEBUG_FILE_ACCESSES || defined UNIV_DEBUG
	ut_a(!block->page.file_page_was_freed);
#endif

	for (i = 0; i < nth_lock; i++) {

		lock = lock_rec_get_next_on_page_const(lock);

		if (!lock) {
			goto function_exit;
		}
	}

	ut_ad(!trx_is_ac_nl_ro(lock->trx));

# ifdef UNIV_SYNC_DEBUG
	/* Only validate the record queues when this thread is not
	holding a space->latch.  Deadlocks are possible due to
	latching order violation when UNIV_DEBUG is defined while
	UNIV_SYNC_DEBUG is not. */
	if (!sync_check_find(SYNC_FSP))
# endif /* UNIV_SYNC_DEBUG */
	for (i = nth_bit; i < lock_rec_get_n_bits(lock); i++) {

		if (i == 1 || lock_rec_get_nth_bit(lock, i)) {

			rec = page_find_rec_with_heap_no(block->frame, i);
			ut_a(rec);
			offsets = rec_get_offsets(rec, lock->index, offsets,
						  ULINT_UNDEFINED, &heap);

			/* If this thread is holding the file space
			latch (fil_space_t::latch), the following
			check WILL break the latching order and may
			cause a deadlock of threads. */

			lock_rec_queue_validate(
				TRUE, block, rec, lock->index, offsets);

			nth_bit = i + 1;

			goto loop;
		}
	}

	nth_bit = 0;
	nth_lock++;

	goto loop;

function_exit:
	lock_mutex_exit();
	mutex_exit(&trx_sys->mutex);

	if (heap != NULL) {
		mem_heap_free(heap);
	}
	return(TRUE);
}

/*********************************************************************//**
Validates the table locks.
@return TRUE if ok */
static
ibool
lock_validate_table_locks(
/*======================*/
	const trx_ut_list_t*	trx_list)	/*!< in: trx list */
{
	const trx_t*	trx;

	ut_ad(lock_mutex_own());
	ut_ad(trx_sys_mutex_own());

	ut_ad(trx_list == &trx_sys->rw_trx_list);

	for (trx = UT_LIST_GET_FIRST(*trx_list);
	     trx != NULL;
	     trx = UT_LIST_GET_NEXT(trx_list, trx)) {

		const lock_t*	lock;

		check_trx_state(trx);

		for (lock = UT_LIST_GET_FIRST(trx->lock.trx_locks);
		     lock != NULL;
		     lock = UT_LIST_GET_NEXT(trx_locks, lock)) {

			if (lock_get_type_low(lock) & LOCK_TABLE) {

				lock_table_queue_validate(
					lock->un_member.tab_lock.table);
			}
		}
	}

	return(TRUE);
}

/*********************************************************************//**
Validate record locks up to a limit.
@return lock at limit or NULL if no more locks in the hash bucket */
static __attribute__((warn_unused_result))
const lock_t*
lock_rec_validate(
/*==============*/
	ulint		start,		/*!< in: lock_sys->rec_hash
					bucket */
	ib_uint64_t*	limit)		/*!< in/out: upper limit of
					(space, page_no) */
{
	ut_ad(lock_mutex_own());
	ut_ad(trx_sys_mutex_own());

	for (const lock_t* lock = static_cast<const lock_t*>(
			HASH_GET_FIRST(lock_sys->rec_hash, start));
	     lock != NULL;
	     lock = static_cast<const lock_t*>(HASH_GET_NEXT(hash, lock))) {

		ib_uint64_t	current;

		ut_ad(!trx_is_ac_nl_ro(lock->trx));
		ut_ad(lock_get_type(lock) == LOCK_REC);

		current = ut_ull_create(
			lock->un_member.rec_lock.space,
			lock->un_member.rec_lock.page_no);

		if (current > *limit) {
			*limit = current + 1;
			return(lock);
		}
	}

	return(0);
}

/*********************************************************************//**
Validate a record lock's block */
static
void
lock_rec_block_validate(
/*====================*/
	ulint		space_id,
	ulint		page_no)
{
	/* The lock and the block that it is referring to may be freed at
	this point. We pass BUF_GET_POSSIBLY_FREED to skip a debug check.
	If the lock exists in lock_rec_validate_page() we assert
	!block->page.file_page_was_freed. */

	buf_block_t*	block;
	mtr_t		mtr;

	/* Make sure that the tablespace is not deleted while we are
	trying to access the page. */
	if (fil_space_t* space = fil_space_acquire(space_id)) {
		mtr_start(&mtr);

		block = buf_page_get_gen(
			page_id_t(space_id, page_no),
			page_size_t(space->flags),
			RW_X_LATCH, NULL,
			BUF_GET_POSSIBLY_FREED,
			__FILE__, __LINE__, &mtr);

		buf_block_dbg_add_level(block, SYNC_NO_ORDER_CHECK);

		ut_ad(lock_rec_validate_page(block));
		mtr_commit(&mtr);

		fil_space_release(space);
	}
}

/*********************************************************************//**
Validates the lock system.
@return TRUE if ok */
static
bool
lock_validate()
/*===========*/
{
	typedef	std::pair<ulint, ulint>		page_addr_t;
	typedef std::set<
		page_addr_t,
		std::less<page_addr_t>,
		ut_allocator<page_addr_t> >	page_addr_set;

	page_addr_set	pages;

	lock_mutex_enter();
	mutex_enter(&trx_sys->mutex);

	ut_a(lock_validate_table_locks(&trx_sys->rw_trx_list));

	/* Iterate over all the record locks and validate the locks. We
	don't want to hog the lock_sys_t::mutex and the trx_sys_t::mutex.
	Release both mutexes during the validation check. */

	for (ulint i = 0; i < hash_get_n_cells(lock_sys->rec_hash); i++) {
		const lock_t*	lock;
		ib_uint64_t	limit = 0;

		while ((lock = lock_rec_validate(i, &limit)) != 0) {

			ulint	space = lock->un_member.rec_lock.space;
			ulint	page_no = lock->un_member.rec_lock.page_no;

			pages.insert(std::make_pair(space, page_no));
		}
	}

	mutex_exit(&trx_sys->mutex);
	lock_mutex_exit();

	for (page_addr_set::const_iterator it = pages.begin();
	     it != pages.end();
	     ++it) {
		lock_rec_block_validate((*it).first, (*it).second);
	}

	return(true);
}
#endif /* UNIV_DEBUG */
/*============ RECORD LOCK CHECKS FOR ROW OPERATIONS ====================*/

/*********************************************************************//**
Checks if locks of other transactions prevent an immediate insert of
a record. If they do, first tests if the query thread should anyway
be suspended for some reason; if not, then puts the transaction and
the query thread to the lock wait state and inserts a waiting request
for a gap x-lock to the lock queue.
@return DB_SUCCESS, DB_LOCK_WAIT, DB_DEADLOCK, or DB_QUE_THR_SUSPENDED */
dberr_t
lock_rec_insert_check_and_lock(
/*===========================*/
	ulint		flags,	/*!< in: if BTR_NO_LOCKING_FLAG bit is
				set, does nothing */
	const rec_t*	rec,	/*!< in: record after which to insert */
	buf_block_t*	block,	/*!< in/out: buffer block of rec */
	dict_index_t*	index,	/*!< in: index */
	que_thr_t*	thr,	/*!< in: query thread */
	mtr_t*		mtr,	/*!< in/out: mini-transaction */
	ibool*		inherit)/*!< out: set to TRUE if the new
				inserted record maybe should inherit
				LOCK_GAP type locks from the successor
				record */
{
	ut_ad(block->frame == page_align(rec));
	ut_ad(!dict_index_is_online_ddl(index)
	      || dict_index_is_clust(index)
	      || (flags & BTR_CREATE_FLAG));
	ut_ad(mtr->is_named_space(index->space));

	if (flags & BTR_NO_LOCKING_FLAG) {

		return(DB_SUCCESS);
	}

	ut_ad(!dict_table_is_temporary(index->table));

	dberr_t		err;
	lock_t*		lock;
	ibool		inherit_in = *inherit;
	trx_t*		trx = thr_get_trx(thr);
	const rec_t*	next_rec = page_rec_get_next_const(rec);
	ulint		heap_no = page_rec_get_heap_no(next_rec);

	lock_mutex_enter();
	/* Because this code is invoked for a running transaction by
	the thread that is serving the transaction, it is not necessary
	to hold trx->mutex here. */

	/* When inserting a record into an index, the table must be at
	least IX-locked. When we are building an index, we would pass
	BTR_NO_LOCKING_FLAG and skip the locking altogether. */
	ut_ad(lock_table_has(trx, index->table, LOCK_IX));

	lock = lock_rec_get_first(lock_sys->rec_hash, block, heap_no);

	if (lock == NULL) {
		/* We optimize CPU time usage in the simplest case */

		lock_mutex_exit();

		if (inherit_in && !dict_index_is_clust(index)) {
			/* Update the page max trx id field */
			page_update_max_trx_id(block,
					       buf_block_get_page_zip(block),
					       trx->id, mtr);
		}

		*inherit = FALSE;

		return(DB_SUCCESS);
	}

	/* Spatial index does not use GAP lock protection. It uses
	"predicate lock" to protect the "range" */
	if (dict_index_is_spatial(index)) {
		return(DB_SUCCESS);
	}

	*inherit = TRUE;

	/* If another transaction has an explicit lock request which locks
	the gap, waiting or granted, on the successor, the insert has to wait.

	An exception is the case where the lock by the another transaction
	is a gap type lock which it placed to wait for its turn to insert. We
	do not consider that kind of a lock conflicting with our insert. This
	eliminates an unnecessary deadlock which resulted when 2 transactions
	had to wait for their insert. Both had waiting gap type lock requests
	on the successor, which produced an unnecessary deadlock. */

	const ulint	type_mode = LOCK_X | LOCK_GAP | LOCK_INSERT_INTENTION;

	const lock_t*	wait_for = lock_rec_other_has_conflicting(
				type_mode, block, heap_no, trx);

	if (wait_for != NULL) {

		RecLock	rec_lock(thr, index, block, heap_no, type_mode);

		trx_mutex_enter(trx);

		err = rec_lock.add_to_waitq(wait_for);

		trx_mutex_exit(trx);

	} else {
		err = DB_SUCCESS;
	}

	lock_mutex_exit();

	switch (err) {
	case DB_SUCCESS_LOCKED_REC:
		err = DB_SUCCESS;
		/* fall through */
	case DB_SUCCESS:
		if (!inherit_in || dict_index_is_clust(index)) {
			break;
		}

		/* Update the page max trx id field */
		page_update_max_trx_id(
			block, buf_block_get_page_zip(block), trx->id, mtr);
	default:
		/* We only care about the two return values. */
		break;
	}

#ifdef UNIV_DEBUG
	{
		mem_heap_t*	heap		= NULL;
		ulint		offsets_[REC_OFFS_NORMAL_SIZE];
		const ulint*	offsets;
		rec_offs_init(offsets_);

		offsets = rec_get_offsets(next_rec, index, offsets_,
					  ULINT_UNDEFINED, &heap);

		ut_ad(lock_rec_queue_validate(
				FALSE, block, next_rec, index, offsets));

		if (heap != NULL) {
			mem_heap_free(heap);
		}
	}
#endif /* UNIV_DEBUG */

	return(err);
}

/*********************************************************************//**
Creates an explicit record lock for a running transaction that currently only
has an implicit lock on the record. The transaction instance must have a
reference count > 0 so that it can't be committed and freed before this
function has completed. */
static
void
lock_rec_convert_impl_to_expl_for_trx(
/*==================================*/
	const buf_block_t*	block,	/*!< in: buffer block of rec */
	const rec_t*		rec,	/*!< in: user record on page */
	dict_index_t*		index,	/*!< in: index of record */
	const ulint*		offsets,/*!< in: rec_get_offsets(rec, index) */
	trx_t*			trx,	/*!< in/out: active transaction */
	ulint			heap_no)/*!< in: rec heap number to lock */
{
	ut_ad(trx_is_referenced(trx));

	DEBUG_SYNC_C("before_lock_rec_convert_impl_to_expl_for_trx");

	lock_mutex_enter();

	ut_ad(!trx_state_eq(trx, TRX_STATE_NOT_STARTED));

	if (!trx_state_eq(trx, TRX_STATE_COMMITTED_IN_MEMORY)
	    && !lock_rec_has_expl(LOCK_X | LOCK_REC_NOT_GAP,
				  block, heap_no, trx)) {

		ulint	type_mode;

		type_mode = (LOCK_REC | LOCK_X | LOCK_REC_NOT_GAP);

		lock_rec_add_to_queue(
			type_mode, block, heap_no, index, trx, FALSE);
	}

	lock_mutex_exit();

	trx_release_reference(trx);

	DEBUG_SYNC_C("after_lock_rec_convert_impl_to_expl_for_trx");
}

/*********************************************************************//**
If a transaction has an implicit x-lock on a record, but no explicit x-lock
set on the record, sets one for it. */
static
void
lock_rec_convert_impl_to_expl(
/*==========================*/
	const buf_block_t*	block,	/*!< in: buffer block of rec */
	const rec_t*		rec,	/*!< in: user record on page */
	dict_index_t*		index,	/*!< in: index of record */
	const ulint*		offsets)/*!< in: rec_get_offsets(rec, index) */
{
	trx_t*		trx;

	ut_ad(!lock_mutex_own());
	ut_ad(page_rec_is_user_rec(rec));
	ut_ad(rec_offs_validate(rec, index, offsets));
	ut_ad(!page_rec_is_comp(rec) == !rec_offs_comp(offsets));

	if (dict_index_is_clust(index)) {
		trx_id_t	trx_id;

		trx_id = lock_clust_rec_some_has_impl(rec, index, offsets);

		trx = trx_rw_is_active(trx_id, NULL, true);
	} else {
		ut_ad(!dict_index_is_online_ddl(index));

		trx = lock_sec_rec_some_has_impl(rec, index, offsets);

		ut_ad(!trx || !lock_rec_other_trx_holds_expl(
				LOCK_S | LOCK_REC_NOT_GAP, trx, rec, block));
	}

	if (trx != 0) {
		ulint	heap_no = page_rec_get_heap_no(rec);

		ut_ad(trx_is_referenced(trx));

		/* If the transaction is still active and has no
		explicit x-lock set on the record, set one for it.
		trx cannot be committed until the ref count is zero. */

		lock_rec_convert_impl_to_expl_for_trx(
			block, rec, index, offsets, trx, heap_no);
	}
}

/*********************************************************************//**
Checks if locks of other transactions prevent an immediate modify (update,
delete mark, or delete unmark) of a clustered index record. If they do,
first tests if the query thread should anyway be suspended for some
reason; if not, then puts the transaction and the query thread to the
lock wait state and inserts a waiting request for a record x-lock to the
lock queue.
@return DB_SUCCESS, DB_LOCK_WAIT, DB_DEADLOCK, or DB_QUE_THR_SUSPENDED */
dberr_t
lock_clust_rec_modify_check_and_lock(
/*=================================*/
	ulint			flags,	/*!< in: if BTR_NO_LOCKING_FLAG
					bit is set, does nothing */
	const buf_block_t*	block,	/*!< in: buffer block of rec */
	const rec_t*		rec,	/*!< in: record which should be
					modified */
	dict_index_t*		index,	/*!< in: clustered index */
	const ulint*		offsets,/*!< in: rec_get_offsets(rec, index) */
	que_thr_t*		thr)	/*!< in: query thread */
{
	dberr_t	err;
	ulint	heap_no;

	ut_ad(rec_offs_validate(rec, index, offsets));
	ut_ad(dict_index_is_clust(index));
	ut_ad(block->frame == page_align(rec));

	if (flags & BTR_NO_LOCKING_FLAG) {

		return(DB_SUCCESS);
	}
	ut_ad(!dict_table_is_temporary(index->table));

	heap_no = rec_offs_comp(offsets)
		? rec_get_heap_no_new(rec)
		: rec_get_heap_no_old(rec);

	/* If a transaction has no explicit x-lock set on the record, set one
	for it */

	lock_rec_convert_impl_to_expl(block, rec, index, offsets);

	lock_mutex_enter();

	ut_ad(lock_table_has(thr_get_trx(thr), index->table, LOCK_IX));

	err = lock_rec_lock(TRUE, LOCK_X | LOCK_REC_NOT_GAP,
			    block, heap_no, index, thr);

	MONITOR_INC(MONITOR_NUM_RECLOCK_REQ);

	lock_mutex_exit();

	ut_ad(lock_rec_queue_validate(FALSE, block, rec, index, offsets));

	if (err == DB_SUCCESS_LOCKED_REC) {
		err = DB_SUCCESS;
	}

	return(err);
}

/*********************************************************************//**
Checks if locks of other transactions prevent an immediate modify (delete
mark or delete unmark) of a secondary index record.
@return DB_SUCCESS, DB_LOCK_WAIT, DB_DEADLOCK, or DB_QUE_THR_SUSPENDED */
dberr_t
lock_sec_rec_modify_check_and_lock(
/*===============================*/
	ulint		flags,	/*!< in: if BTR_NO_LOCKING_FLAG
				bit is set, does nothing */
	buf_block_t*	block,	/*!< in/out: buffer block of rec */
	const rec_t*	rec,	/*!< in: record which should be
				modified; NOTE: as this is a secondary
				index, we always have to modify the
				clustered index record first: see the
				comment below */
	dict_index_t*	index,	/*!< in: secondary index */
	que_thr_t*	thr,	/*!< in: query thread
				(can be NULL if BTR_NO_LOCKING_FLAG) */
	mtr_t*		mtr)	/*!< in/out: mini-transaction */
{
	dberr_t	err;
	ulint	heap_no;

	ut_ad(!dict_index_is_clust(index));
	ut_ad(!dict_index_is_online_ddl(index) || (flags & BTR_CREATE_FLAG));
	ut_ad(block->frame == page_align(rec));
	ut_ad(mtr->is_named_space(index->space));

	if (flags & BTR_NO_LOCKING_FLAG) {

		return(DB_SUCCESS);
	}
	ut_ad(!dict_table_is_temporary(index->table));

	heap_no = page_rec_get_heap_no(rec);

	/* Another transaction cannot have an implicit lock on the record,
	because when we come here, we already have modified the clustered
	index record, and this would not have been possible if another active
	transaction had modified this secondary index record. */

	lock_mutex_enter();

	ut_ad(lock_table_has(thr_get_trx(thr), index->table, LOCK_IX));

	err = lock_rec_lock(TRUE, LOCK_X | LOCK_REC_NOT_GAP,
			    block, heap_no, index, thr);

	MONITOR_INC(MONITOR_NUM_RECLOCK_REQ);

	lock_mutex_exit();

#ifdef UNIV_DEBUG
	{
		mem_heap_t*	heap		= NULL;
		ulint		offsets_[REC_OFFS_NORMAL_SIZE];
		const ulint*	offsets;
		rec_offs_init(offsets_);

		offsets = rec_get_offsets(rec, index, offsets_,
					  ULINT_UNDEFINED, &heap);

		ut_ad(lock_rec_queue_validate(
			FALSE, block, rec, index, offsets));

		if (heap != NULL) {
			mem_heap_free(heap);
		}
	}
#endif /* UNIV_DEBUG */

	if (err == DB_SUCCESS || err == DB_SUCCESS_LOCKED_REC) {
		/* Update the page max trx id field */
		/* It might not be necessary to do this if
		err == DB_SUCCESS (no new lock created),
		but it should not cost too much performance. */
		page_update_max_trx_id(block,
				       buf_block_get_page_zip(block),
				       thr_get_trx(thr)->id, mtr);
		err = DB_SUCCESS;
	}

	return(err);
}

/*********************************************************************//**
Like lock_clust_rec_read_check_and_lock(), but reads a
secondary index record.
@return DB_SUCCESS, DB_SUCCESS_LOCKED_REC, DB_LOCK_WAIT, DB_DEADLOCK,
or DB_QUE_THR_SUSPENDED */
dberr_t
lock_sec_rec_read_check_and_lock(
/*=============================*/
	ulint			flags,	/*!< in: if BTR_NO_LOCKING_FLAG
					bit is set, does nothing */
	const buf_block_t*	block,	/*!< in: buffer block of rec */
	const rec_t*		rec,	/*!< in: user record or page
					supremum record which should
					be read or passed over by a
					read cursor */
	dict_index_t*		index,	/*!< in: secondary index */
	const ulint*		offsets,/*!< in: rec_get_offsets(rec, index) */
	lock_mode		mode,	/*!< in: mode of the lock which
					the read cursor should set on
					records: LOCK_S or LOCK_X; the
					latter is possible in
					SELECT FOR UPDATE */
	ulint			gap_mode,/*!< in: LOCK_ORDINARY, LOCK_GAP, or
					LOCK_REC_NOT_GAP */
	que_thr_t*		thr)	/*!< in: query thread */
{
	dberr_t	err;
	ulint	heap_no;

	ut_ad(!dict_index_is_clust(index));
	ut_ad(!dict_index_is_online_ddl(index));
	ut_ad(block->frame == page_align(rec));
	ut_ad(page_rec_is_user_rec(rec) || page_rec_is_supremum(rec));
	ut_ad(rec_offs_validate(rec, index, offsets));
	ut_ad(mode == LOCK_X || mode == LOCK_S);

	if ((flags & BTR_NO_LOCKING_FLAG)
	    || srv_read_only_mode
	    || dict_table_is_temporary(index->table)) {

		return(DB_SUCCESS);
	}

	heap_no = page_rec_get_heap_no(rec);

	/* Some transaction may have an implicit x-lock on the record only
	if the max trx id for the page >= min trx id for the trx list or a
	database recovery is running. */

	if ((page_get_max_trx_id(block->frame) >= trx_rw_min_trx_id()
	     || recv_recovery_is_on())
	    && !page_rec_is_supremum(rec)) {

		lock_rec_convert_impl_to_expl(block, rec, index, offsets);
	}

	lock_mutex_enter();

	ut_ad(mode != LOCK_X
	      || lock_table_has(thr_get_trx(thr), index->table, LOCK_IX));
	ut_ad(mode != LOCK_S
	      || lock_table_has(thr_get_trx(thr), index->table, LOCK_IS));

	err = lock_rec_lock(FALSE, mode | gap_mode,
			    block, heap_no, index, thr);

	MONITOR_INC(MONITOR_NUM_RECLOCK_REQ);

	lock_mutex_exit();

	ut_ad(lock_rec_queue_validate(FALSE, block, rec, index, offsets));

	return(err);
}

/*********************************************************************//**
Checks if locks of other transactions prevent an immediate read, or passing
over by a read cursor, of a clustered index record. If they do, first tests
if the query thread should anyway be suspended for some reason; if not, then
puts the transaction and the query thread to the lock wait state and inserts a
waiting request for a record lock to the lock queue. Sets the requested mode
lock on the record.
@return DB_SUCCESS, DB_SUCCESS_LOCKED_REC, DB_LOCK_WAIT, DB_DEADLOCK,
or DB_QUE_THR_SUSPENDED */
dberr_t
lock_clust_rec_read_check_and_lock(
/*===============================*/
	ulint			flags,	/*!< in: if BTR_NO_LOCKING_FLAG
					bit is set, does nothing */
	const buf_block_t*	block,	/*!< in: buffer block of rec */
	const rec_t*		rec,	/*!< in: user record or page
					supremum record which should
					be read or passed over by a
					read cursor */
	dict_index_t*		index,	/*!< in: clustered index */
	const ulint*		offsets,/*!< in: rec_get_offsets(rec, index) */
	lock_mode		mode,	/*!< in: mode of the lock which
					the read cursor should set on
					records: LOCK_S or LOCK_X; the
					latter is possible in
					SELECT FOR UPDATE */
	ulint			gap_mode,/*!< in: LOCK_ORDINARY, LOCK_GAP, or
					LOCK_REC_NOT_GAP */
	que_thr_t*		thr)	/*!< in: query thread */
{
	dberr_t	err;
	ulint	heap_no;

	ut_ad(dict_index_is_clust(index));
	ut_ad(block->frame == page_align(rec));
	ut_ad(page_rec_is_user_rec(rec) || page_rec_is_supremum(rec));
	ut_ad(gap_mode == LOCK_ORDINARY || gap_mode == LOCK_GAP
	      || gap_mode == LOCK_REC_NOT_GAP);
	ut_ad(rec_offs_validate(rec, index, offsets));

	if ((flags & BTR_NO_LOCKING_FLAG)
	    || srv_read_only_mode
	    || dict_table_is_temporary(index->table)) {

		return(DB_SUCCESS);
	}

	heap_no = page_rec_get_heap_no(rec);

	if (heap_no != PAGE_HEAP_NO_SUPREMUM) {

		lock_rec_convert_impl_to_expl(block, rec, index, offsets);
	}

	lock_mutex_enter();

	ut_ad(mode != LOCK_X
	      || lock_table_has(thr_get_trx(thr), index->table, LOCK_IX));
	ut_ad(mode != LOCK_S
	      || lock_table_has(thr_get_trx(thr), index->table, LOCK_IS));

	err = lock_rec_lock(FALSE, mode | gap_mode, block, heap_no, index, thr);

	MONITOR_INC(MONITOR_NUM_RECLOCK_REQ);

	lock_mutex_exit();

	ut_ad(lock_rec_queue_validate(FALSE, block, rec, index, offsets));

	DEBUG_SYNC_C("after_lock_clust_rec_read_check_and_lock");

	return(err);
}
/*********************************************************************//**
Checks if locks of other transactions prevent an immediate read, or passing
over by a read cursor, of a clustered index record. If they do, first tests
if the query thread should anyway be suspended for some reason; if not, then
puts the transaction and the query thread to the lock wait state and inserts a
waiting request for a record lock to the lock queue. Sets the requested mode
lock on the record. This is an alternative version of
lock_clust_rec_read_check_and_lock() that does not require the parameter
"offsets".
@return DB_SUCCESS, DB_LOCK_WAIT, DB_DEADLOCK, or DB_QUE_THR_SUSPENDED */
dberr_t
lock_clust_rec_read_check_and_lock_alt(
/*===================================*/
	ulint			flags,	/*!< in: if BTR_NO_LOCKING_FLAG
					bit is set, does nothing */
	const buf_block_t*	block,	/*!< in: buffer block of rec */
	const rec_t*		rec,	/*!< in: user record or page
					supremum record which should
					be read or passed over by a
					read cursor */
	dict_index_t*		index,	/*!< in: clustered index */
	lock_mode		mode,	/*!< in: mode of the lock which
					the read cursor should set on
					records: LOCK_S or LOCK_X; the
					latter is possible in
					SELECT FOR UPDATE */
	ulint			gap_mode,/*!< in: LOCK_ORDINARY, LOCK_GAP, or
					LOCK_REC_NOT_GAP */
	que_thr_t*		thr)	/*!< in: query thread */
{
	mem_heap_t*	tmp_heap	= NULL;
	ulint		offsets_[REC_OFFS_NORMAL_SIZE];
	ulint*		offsets		= offsets_;
	dberr_t		err;
	rec_offs_init(offsets_);

	offsets = rec_get_offsets(rec, index, offsets,
				  ULINT_UNDEFINED, &tmp_heap);
	err = lock_clust_rec_read_check_and_lock(flags, block, rec, index,
						 offsets, mode, gap_mode, thr);
	if (tmp_heap) {
		mem_heap_free(tmp_heap);
	}

	if (err == DB_SUCCESS_LOCKED_REC) {
		err = DB_SUCCESS;
	}

	return(err);
}

/*******************************************************************//**
Release the last lock from the transaction's autoinc locks. */
UNIV_INLINE
void
lock_release_autoinc_last_lock(
/*===========================*/
	ib_vector_t*	autoinc_locks)	/*!< in/out: vector of AUTOINC locks */
{
	ulint		last;
	lock_t*		lock;

	ut_ad(lock_mutex_own());
	ut_a(!ib_vector_is_empty(autoinc_locks));

	/* The lock to be release must be the last lock acquired. */
	last = ib_vector_size(autoinc_locks) - 1;
	lock = *static_cast<lock_t**>(ib_vector_get(autoinc_locks, last));

	/* Should have only AUTOINC locks in the vector. */
	ut_a(lock_get_mode(lock) == LOCK_AUTO_INC);
	ut_a(lock_get_type(lock) == LOCK_TABLE);

	ut_a(lock->un_member.tab_lock.table != NULL);

	/* This will remove the lock from the trx autoinc_locks too. */
	lock_table_dequeue(lock);

	/* Remove from the table vector too. */
	lock_trx_table_locks_remove(lock);
}

/*******************************************************************//**
Check if a transaction holds any autoinc locks.
@return TRUE if the transaction holds any AUTOINC locks. */
static
ibool
lock_trx_holds_autoinc_locks(
/*=========================*/
	const trx_t*	trx)		/*!< in: transaction */
{
	ut_a(trx->autoinc_locks != NULL);

	return(!ib_vector_is_empty(trx->autoinc_locks));
}

/*******************************************************************//**
Release all the transaction's autoinc locks. */
static
void
lock_release_autoinc_locks(
/*=======================*/
	trx_t*		trx)		/*!< in/out: transaction */
{
	ut_ad(lock_mutex_own());
	/* If this is invoked for a running transaction by the thread
	that is serving the transaction, then it is not necessary to
	hold trx->mutex here. */

	ut_a(trx->autoinc_locks != NULL);

	/* We release the locks in the reverse order. This is to
	avoid searching the vector for the element to delete at
	the lower level. See (lock_table_remove_low()) for details. */
	while (!ib_vector_is_empty(trx->autoinc_locks)) {

		/* lock_table_remove_low() will also remove the lock from
		the transaction's autoinc_locks vector. */
		lock_release_autoinc_last_lock(trx->autoinc_locks);
	}

	/* Should release all locks. */
	ut_a(ib_vector_is_empty(trx->autoinc_locks));
}

/*******************************************************************//**
Gets the type of a lock. Non-inline version for using outside of the
lock module.
@return LOCK_TABLE or LOCK_REC */
ulint
lock_get_type(
/*==========*/
	const lock_t*	lock)	/*!< in: lock */
{
	return(lock_get_type_low(lock));
}

/*******************************************************************//**
Gets the id of the transaction owning a lock.
@return transaction id */
trx_id_t
lock_get_trx_id(
/*============*/
	const lock_t*	lock)	/*!< in: lock */
{
	return(trx_get_id_for_print(lock->trx));
}

/*******************************************************************//**
Gets the mode of a lock in a human readable string.
The string should not be free()'d or modified.
@return lock mode */
const char*
lock_get_mode_str(
/*==============*/
	const lock_t*	lock)	/*!< in: lock */
{
	ibool	is_gap_lock;

	is_gap_lock = lock_get_type_low(lock) == LOCK_REC
		&& lock_rec_get_gap(lock);

	switch (lock_get_mode(lock)) {
	case LOCK_S:
		if (is_gap_lock) {
			return("S,GAP");
		} else {
			return("S");
		}
	case LOCK_X:
		if (is_gap_lock) {
			return("X,GAP");
		} else {
			return("X");
		}
	case LOCK_IS:
		if (is_gap_lock) {
			return("IS,GAP");
		} else {
			return("IS");
		}
	case LOCK_IX:
		if (is_gap_lock) {
			return("IX,GAP");
		} else {
			return("IX");
		}
	case LOCK_AUTO_INC:
		return("AUTO_INC");
	default:
		return("UNKNOWN");
	}
}

/*******************************************************************//**
Gets the type of a lock in a human readable string.
The string should not be free()'d or modified.
@return lock type */
const char*
lock_get_type_str(
/*==============*/
	const lock_t*	lock)	/*!< in: lock */
{
	switch (lock_get_type_low(lock)) {
	case LOCK_REC:
		return("RECORD");
	case LOCK_TABLE:
		return("TABLE");
	default:
		return("UNKNOWN");
	}
}

/*******************************************************************//**
Gets the table on which the lock is.
@return table */
UNIV_INLINE
dict_table_t*
lock_get_table(
/*===========*/
	const lock_t*	lock)	/*!< in: lock */
{
	switch (lock_get_type_low(lock)) {
	case LOCK_REC:
		ut_ad(dict_index_is_clust(lock->index)
		      || !dict_index_is_online_ddl(lock->index));
		return(lock->index->table);
	case LOCK_TABLE:
		return(lock->un_member.tab_lock.table);
	default:
		ut_error;
		return(NULL);
	}
}

/*******************************************************************//**
Gets the id of the table on which the lock is.
@return id of the table */
table_id_t
lock_get_table_id(
/*==============*/
	const lock_t*	lock)	/*!< in: lock */
{
	dict_table_t*	table;

	table = lock_get_table(lock);

	return(table->id);
}

/** Determine which table a lock is associated with.
@param[in]	lock	the lock
@return name of the table */
const table_name_t&
lock_get_table_name(
	const lock_t*	lock)
{
	return(lock_get_table(lock)->name);
}

/*******************************************************************//**
For a record lock, gets the index on which the lock is.
@return index */
const dict_index_t*
lock_rec_get_index(
/*===============*/
	const lock_t*	lock)	/*!< in: lock */
{
	ut_a(lock_get_type_low(lock) == LOCK_REC);
	ut_ad(dict_index_is_clust(lock->index)
	      || !dict_index_is_online_ddl(lock->index));

	return(lock->index);
}

/*******************************************************************//**
For a record lock, gets the name of the index on which the lock is.
The string should not be free()'d or modified.
@return name of the index */
const char*
lock_rec_get_index_name(
/*====================*/
	const lock_t*	lock)	/*!< in: lock */
{
	ut_a(lock_get_type_low(lock) == LOCK_REC);
	ut_ad(dict_index_is_clust(lock->index)
	      || !dict_index_is_online_ddl(lock->index));

	return(lock->index->name);
}

/*******************************************************************//**
For a record lock, gets the tablespace number on which the lock is.
@return tablespace number */
ulint
lock_rec_get_space_id(
/*==================*/
	const lock_t*	lock)	/*!< in: lock */
{
	ut_a(lock_get_type_low(lock) == LOCK_REC);

	return(lock->un_member.rec_lock.space);
}

/*******************************************************************//**
For a record lock, gets the page number on which the lock is.
@return page number */
ulint
lock_rec_get_page_no(
/*=================*/
	const lock_t*	lock)	/*!< in: lock */
{
	ut_a(lock_get_type_low(lock) == LOCK_REC);

	return(lock->un_member.rec_lock.page_no);
}

/*********************************************************************//**
Cancels a waiting lock request and releases possible other transactions
waiting behind it. */
void
lock_cancel_waiting_and_release(
/*============================*/
	lock_t*	lock)	/*!< in/out: waiting lock request */
{
	que_thr_t*	thr;

	ut_ad(lock_mutex_own());
	ut_ad(trx_mutex_own(lock->trx));

	lock->trx->lock.cancel = true;

	if (lock_get_type_low(lock) == LOCK_REC) {

		lock_rec_dequeue_from_page(lock);
	} else {
		ut_ad(lock_get_type_low(lock) & LOCK_TABLE);

		if (lock->trx->autoinc_locks != NULL) {
			/* Release the transaction's AUTOINC locks. */
			lock_release_autoinc_locks(lock->trx);
		}

		lock_table_dequeue(lock);
	}

	/* Reset the wait flag and the back pointer to lock in trx. */

	lock_reset_lock_and_trx_wait(lock);

	/* The following function releases the trx from lock wait. */

	thr = que_thr_end_lock_wait(lock->trx);

	if (thr != NULL) {
		lock_wait_release_thread_if_suspended(thr);
	}

	lock->trx->lock.cancel = false;
}

/*********************************************************************//**
Unlocks AUTO_INC type locks that were possibly reserved by a trx. This
function should be called at the the end of an SQL statement, by the
connection thread that owns the transaction (trx->mysql_thd). */
void
lock_unlock_table_autoinc(
/*======================*/
	trx_t*	trx)	/*!< in/out: transaction */
{
	ut_ad(!lock_mutex_own());
	ut_ad(!trx_mutex_own(trx));
	ut_ad(!trx->lock.wait_lock);

	/* This can be invoked on NOT_STARTED, ACTIVE, PREPARED,
	but not COMMITTED transactions. */

	ut_ad(trx_state_eq(trx, TRX_STATE_NOT_STARTED)
	      || trx_state_eq(trx, TRX_STATE_FORCED_ROLLBACK)
	      || !trx_state_eq(trx, TRX_STATE_COMMITTED_IN_MEMORY));

	/* This function is invoked for a running transaction by the
	thread that is serving the transaction. Therefore it is not
	necessary to hold trx->mutex here. */

	if (lock_trx_holds_autoinc_locks(trx)) {
		lock_mutex_enter();

		lock_release_autoinc_locks(trx);

		lock_mutex_exit();
	}
}

/*********************************************************************//**
Releases a transaction's locks, and releases possible other transactions
waiting because of these locks. Change the state of the transaction to
TRX_STATE_COMMITTED_IN_MEMORY. */
void
lock_trx_release_locks(
/*===================*/
	trx_t*	trx)	/*!< in/out: transaction */
{
	check_trx_state(trx);

	if (trx_state_eq(trx, TRX_STATE_PREPARED)) {

		mutex_enter(&trx_sys->mutex);

		ut_a(trx_sys->n_prepared_trx > 0);
		--trx_sys->n_prepared_trx;

		if (trx->is_recovered) {
			ut_a(trx_sys->n_prepared_recovered_trx > 0);
			trx_sys->n_prepared_recovered_trx--;
		}

		mutex_exit(&trx_sys->mutex);
	} else {
		ut_ad(trx_state_eq(trx, TRX_STATE_ACTIVE));
	}

	/* The transition of trx->state to TRX_STATE_COMMITTED_IN_MEMORY
	is protected by both the lock_sys->mutex and the trx->mutex. */
	lock_mutex_enter();

	trx_mutex_enter(trx);

	/* The following assignment makes the transaction committed in memory
	and makes its changes to data visible to other transactions.
	NOTE that there is a small discrepancy from the strict formal
	visibility rules here: a human user of the database can see
	modifications made by another transaction T even before the necessary
	log segment has been flushed to the disk. If the database happens to
	crash before the flush, the user has seen modifications from T which
	will never be a committed transaction. However, any transaction T2
	which sees the modifications of the committing transaction T, and
	which also itself makes modifications to the database, will get an lsn
	larger than the committing transaction T. In the case where the log
	flush fails, and T never gets committed, also T2 will never get
	committed. */

	/*--------------------------------------*/
	trx->state = TRX_STATE_COMMITTED_IN_MEMORY;
	/*--------------------------------------*/

	if (trx_is_referenced(trx)) {

		lock_mutex_exit();

		while (trx_is_referenced(trx)) {

			trx_mutex_exit(trx);

			DEBUG_SYNC_C("waiting_trx_is_not_referenced");

			/** Doing an implicit to explicit conversion
			should not be expensive. */
			ut_delay(ut_rnd_interval(0, srv_spin_wait_delay));

			trx_mutex_enter(trx);
		}

		trx_mutex_exit(trx);

		lock_mutex_enter();

		trx_mutex_enter(trx);
	}

	ut_ad(!trx_is_referenced(trx));

	/* If the background thread trx_rollback_or_clean_recovered()
	is still active then there is a chance that the rollback
	thread may see this trx as COMMITTED_IN_MEMORY and goes ahead
	to clean it up calling trx_cleanup_at_db_startup(). This can
	happen in the case we are committing a trx here that is left
	in PREPARED state during the crash. Note that commit of the
	rollback of a PREPARED trx happens in the recovery thread
	while the rollback of other transactions happen in the
	background thread. To avoid this race we unconditionally unset
	the is_recovered flag. */

	trx->is_recovered = false;

	trx_mutex_exit(trx);

	lock_release(trx);

	trx->lock.n_rec_locks = 0;

	lock_mutex_exit();

	/* We don't remove the locks one by one from the vector for
	efficiency reasons. We simply reset it because we would have
	released all the locks anyway. */

	trx->lock.table_locks.clear();

	ut_a(UT_LIST_GET_LEN(trx->lock.trx_locks) == 0);
	ut_a(ib_vector_is_empty(trx->autoinc_locks));
	ut_a(trx->lock.table_locks.empty());

	mem_heap_empty(trx->lock.lock_heap);
}

/*********************************************************************//**
Check whether the transaction has already been rolled back because it
was selected as a deadlock victim, or if it has to wait then cancel
the wait lock.
@return DB_DEADLOCK, DB_LOCK_WAIT or DB_SUCCESS */
dberr_t
lock_trx_handle_wait(
/*=================*/
	trx_t*	trx)	/*!< in/out: trx lock state */
{
	dberr_t	err;

	lock_mutex_enter();

	trx_mutex_enter(trx);

	if (trx->lock.was_chosen_as_deadlock_victim) {
		err = DB_DEADLOCK;
	} else if (trx->lock.wait_lock != NULL) {
		lock_cancel_waiting_and_release(trx->lock.wait_lock);
		err = DB_LOCK_WAIT;
	} else {
		/* The lock was probably granted before we got here. */
		err = DB_SUCCESS;
	}

	lock_mutex_exit();

	trx_mutex_exit(trx);

	return(err);
}

/*********************************************************************//**
Get the number of locks on a table.
@return number of locks */
ulint
lock_table_get_n_locks(
/*===================*/
	const dict_table_t*	table)	/*!< in: table */
{
	ulint		n_table_locks;

	lock_mutex_enter();

	n_table_locks = UT_LIST_GET_LEN(table->locks);

	lock_mutex_exit();

	return(n_table_locks);
}

#ifdef UNIV_DEBUG
/*******************************************************************//**
Do an exhaustive check for any locks (table or rec) against the table.
@return lock if found */
static
const lock_t*
lock_table_locks_lookup(
/*====================*/
	const dict_table_t*	table,		/*!< in: check if there are
						any locks held on records in
						this table or on the table
						itself */
	const trx_ut_list_t*	trx_list)	/*!< in: trx list to check */
{
	trx_t*			trx;

	ut_a(table != NULL);
	ut_ad(lock_mutex_own());
	ut_ad(trx_sys_mutex_own());

	for (trx = UT_LIST_GET_FIRST(*trx_list);
	     trx != NULL;
	     trx = UT_LIST_GET_NEXT(trx_list, trx)) {

		const lock_t*	lock;

		check_trx_state(trx);

		for (lock = UT_LIST_GET_FIRST(trx->lock.trx_locks);
		     lock != NULL;
		     lock = UT_LIST_GET_NEXT(trx_locks, lock)) {

			ut_a(lock->trx == trx);

			if (lock_get_type_low(lock) == LOCK_REC) {
				ut_ad(!dict_index_is_online_ddl(lock->index)
				      || dict_index_is_clust(lock->index));
				if (lock->index->table == table) {
					return(lock);
				}
			} else if (lock->un_member.tab_lock.table == table) {
				return(lock);
			}
		}
	}

	return(NULL);
}
#endif /* UNIV_DEBUG */

/*******************************************************************//**
Check if there are any locks (table or rec) against table.
@return true if table has either table or record locks. */
bool
lock_table_has_locks(
/*=================*/
	const dict_table_t*	table)	/*!< in: check if there are any locks
					held on records in this table or on the
					table itself */
{
	ibool			has_locks;

	lock_mutex_enter();

	has_locks = UT_LIST_GET_LEN(table->locks) > 0 || table->n_rec_locks > 0;

#ifdef UNIV_DEBUG
	if (!has_locks) {
		mutex_enter(&trx_sys->mutex);

		ut_ad(!lock_table_locks_lookup(table, &trx_sys->rw_trx_list));

		mutex_exit(&trx_sys->mutex);
	}
#endif /* UNIV_DEBUG */

	lock_mutex_exit();

	return(has_locks);
}

/*******************************************************************//**
Initialise the table lock list. */
void
lock_table_lock_list_init(
/*======================*/
	table_lock_list_t*	lock_list)	/*!< List to initialise */
{
	UT_LIST_INIT(*lock_list, &lock_table_t::locks);
}

/*******************************************************************//**
Initialise the trx lock list. */
void
lock_trx_lock_list_init(
/*====================*/
	trx_lock_list_t*	lock_list)	/*!< List to initialise */
{
	UT_LIST_INIT(*lock_list, &lock_t::trx_locks);
}

/*******************************************************************//**
Set the lock system timeout event. */
void
lock_set_timeout_event()
/*====================*/
{
	os_event_set(lock_sys->timeout_event);
}

#ifdef UNIV_DEBUG
/*******************************************************************//**
Check if the transaction holds any locks on the sys tables
or its records.
@return the strongest lock found on any sys table or 0 for none */
const lock_t*
lock_trx_has_sys_table_locks(
/*=========================*/
	const trx_t*	trx)	/*!< in: transaction to check */
{
	const lock_t*	strongest_lock = 0;
	lock_mode	strongest = LOCK_NONE;

	lock_mutex_enter();

	typedef lock_pool_t::const_reverse_iterator iterator;

	iterator	end = trx->lock.table_locks.rend();
	iterator	it = trx->lock.table_locks.rbegin();

	/* Find a valid mode. Note: ib_vector_size() can be 0. */

	for (/* No op */; it != end; ++it) {
		const lock_t*	lock = *it;

		if (lock != NULL
		    && dict_is_sys_table(lock->un_member.tab_lock.table->id)) {

			strongest = lock_get_mode(lock);
			ut_ad(strongest != LOCK_NONE);
			strongest_lock = lock;
			break;
		}
	}

	if (strongest == LOCK_NONE) {
		lock_mutex_exit();
		return(NULL);
	}

	for (/* No op */; it != end; ++it) {
		const lock_t*	lock = *it;

		if (lock == NULL) {
			continue;
		}

		ut_ad(trx == lock->trx);
		ut_ad(lock_get_type_low(lock) & LOCK_TABLE);
		ut_ad(lock->un_member.tab_lock.table != NULL);

		lock_mode	mode = lock_get_mode(lock);

		if (dict_is_sys_table(lock->un_member.tab_lock.table->id)
		    && lock_mode_stronger_or_eq(mode, strongest)) {

			strongest = mode;
			strongest_lock = lock;
		}
	}

	lock_mutex_exit();

	return(strongest_lock);
}

/*******************************************************************//**
Check if the transaction holds an exclusive lock on a record.
@return whether the locks are held */
bool
lock_trx_has_rec_x_lock(
/*====================*/
	const trx_t*		trx,	/*!< in: transaction to check */
	const dict_table_t*	table,	/*!< in: table to check */
	const buf_block_t*	block,	/*!< in: buffer block of the record */
	ulint			heap_no)/*!< in: record heap number */
{
	ut_ad(heap_no > PAGE_HEAP_NO_SUPREMUM);

	lock_mutex_enter();
	ut_a(lock_table_has(trx, table, LOCK_IX)
	     || dict_table_is_temporary(table));
	ut_a(lock_rec_has_expl(LOCK_X | LOCK_REC_NOT_GAP,
			       block, heap_no, trx)
	     || dict_table_is_temporary(table));
	lock_mutex_exit();
	return(true);
}
#endif /* UNIV_DEBUG */

/** rewind(3) the file used for storing the latest detected deadlock and
print a heading message to stderr if printing of all deadlocks to stderr
is enabled. */
void
DeadlockChecker::start_print()
{
	ut_ad(lock_mutex_own());

	rewind(lock_latest_err_file);
	ut_print_timestamp(lock_latest_err_file);

	if (srv_print_all_deadlocks) {
		ib::info() << "Transactions deadlock detected, dumping"
			<< " detailed information.";
	}
}

/** Print a message to the deadlock file and possibly to stderr.
@param msg message to print */
void
DeadlockChecker::print(const char* msg)
{
	fputs(msg, lock_latest_err_file);

	if (srv_print_all_deadlocks) {
		ib::info() << msg;
	}
}

/** Print transaction data to the deadlock file and possibly to stderr.
@param trx transaction
@param max_query_len max query length to print */
void
DeadlockChecker::print(const trx_t* trx, ulint max_query_len)
{
	ut_ad(lock_mutex_own());

	ulint	n_rec_locks = lock_number_of_rows_locked(&trx->lock);
	ulint	n_trx_locks = UT_LIST_GET_LEN(trx->lock.trx_locks);
	ulint	heap_size = mem_heap_get_size(trx->lock.lock_heap);

	mutex_enter(&trx_sys->mutex);

	trx_print_low(lock_latest_err_file, trx, max_query_len,
		      n_rec_locks, n_trx_locks, heap_size);

	if (srv_print_all_deadlocks) {
		trx_print_low(stderr, trx, max_query_len,
			      n_rec_locks, n_trx_locks, heap_size);
	}

	mutex_exit(&trx_sys->mutex);
}

/** Print lock data to the deadlock file and possibly to stderr.
@param lock record or table type lock */
void
DeadlockChecker::print(const lock_t* lock)
{
	ut_ad(lock_mutex_own());

	if (lock_get_type_low(lock) == LOCK_REC) {
		lock_rec_print(lock_latest_err_file, lock);

		if (srv_print_all_deadlocks) {
			lock_rec_print(stderr, lock);
		}
	} else {
		lock_table_print(lock_latest_err_file, lock);

		if (srv_print_all_deadlocks) {
			lock_table_print(stderr, lock);
		}
	}
}

/** Get the next lock in the queue that is owned by a transaction whose
sub-tree has not already been searched.
Note: "next" here means PREV for table locks.

@param lock Lock in queue
@param heap_no heap_no if lock is a record lock else ULINT_UNDEFINED

@return next lock or NULL if at end of queue */
const lock_t*
DeadlockChecker::get_next_lock(const lock_t* lock, ulint heap_no) const
{
	ut_ad(lock_mutex_own());

	do {
		if (lock_get_type_low(lock) == LOCK_REC) {
			ut_ad(heap_no != ULINT_UNDEFINED);
			lock = lock_rec_get_next_const(heap_no, lock);
		} else {
			ut_ad(heap_no == ULINT_UNDEFINED);
			ut_ad(lock_get_type_low(lock) == LOCK_TABLE);

			lock = UT_LIST_GET_PREV(
				un_member.tab_lock.locks, lock);
		}

	} while (lock != NULL && is_visited(lock));

	ut_ad(lock == NULL
	      || lock_get_type_low(lock) == lock_get_type_low(m_wait_lock));

	return(lock);
}

/** Get the first lock to search. The search starts from the current
wait_lock. What we are really interested in is an edge from the
current wait_lock's owning transaction to another transaction that has
a lock ahead in the queue. We skip locks where the owning transaction's
sub-tree has already been searched.

Note: The record locks are traversed from the oldest lock to the
latest. For table locks we go from latest to oldest.

For record locks, we first position the "iterator" on the first lock on
the page and then reposition on the actual heap_no. This is required
due to the way the record lock has is implemented.

@param[out] heap_no if rec lock, else ULINT_UNDEFINED.
@return first lock or NULL */
const lock_t*
DeadlockChecker::get_first_lock(ulint* heap_no) const
{
	ut_ad(lock_mutex_own());

	const lock_t*	lock = m_wait_lock;

	if (lock_get_type_low(lock) == LOCK_REC) {
		hash_table_t*	lock_hash;

		lock_hash = lock->type_mode & LOCK_PREDICATE
			? lock_sys->prdt_hash
			: lock_sys->rec_hash;

		/* We are only interested in records that match the heap_no. */
		*heap_no = lock_rec_find_set_bit(lock);

		ut_ad(*heap_no <= 0xffff);
		ut_ad(*heap_no != ULINT_UNDEFINED);

		/* Find the locks on the page. */
		lock = lock_rec_get_first_on_page_addr(
			lock_hash,
			lock->un_member.rec_lock.space,
			lock->un_member.rec_lock.page_no);

		/* Position on the first lock on the physical record.*/
		if (!lock_rec_get_nth_bit(lock, *heap_no)) {
			lock = lock_rec_get_next_const(*heap_no, lock);
		}

		ut_a(!lock_get_wait(lock));
	} else {
		/* Table locks don't care about the heap_no. */
		*heap_no = ULINT_UNDEFINED;
		ut_ad(lock_get_type_low(lock) == LOCK_TABLE);
		lock = UT_LIST_GET_PREV(un_member.tab_lock.locks, lock);
	}

	/* Must find at least two locks, otherwise there cannot be a
	waiting lock, secondly the first lock cannot be the wait_lock. */
	ut_a(lock != NULL);
	ut_a(lock != m_wait_lock);

	/* Check that the lock type doesn't change. */
	ut_ad(lock_get_type_low(lock) == lock_get_type_low(m_wait_lock));

	return(lock);
}

/** Notify that a deadlock has been detected and print the conflicting
transaction info.
@param lock lock causing deadlock */
void
DeadlockChecker::notify(const lock_t* lock) const
{
	ut_ad(lock_mutex_own());

	start_print();

	print("\n*** (1) TRANSACTION:\n");

	print(m_wait_lock->trx, 3000);

	print("*** (1) WAITING FOR THIS LOCK TO BE GRANTED:\n");

	print(m_wait_lock);

	print("*** (2) TRANSACTION:\n");

	print(lock->trx, 3000);

	print("*** (2) HOLDS THE LOCK(S):\n");

	print(lock);

	/* It is possible that the joining transaction was granted its
	lock when we rolled back some other waiting transaction. */

	if (m_start->lock.wait_lock != 0) {
		print("*** (2) WAITING FOR THIS LOCK TO BE GRANTED:\n");

		print(m_start->lock.wait_lock);
	}

	DBUG_PRINT("ib_lock", ("deadlock detected"));
}

/** Select the victim transaction that should be rolledback.
@return victim transaction */
const trx_t*
DeadlockChecker::select_victim() const
{
	ut_ad(lock_mutex_own());
	ut_ad(m_start->lock.wait_lock != 0);
	ut_ad(m_wait_lock->trx != m_start);

	if (thd_trx_priority(m_start->mysql_thd) > 0
	    || thd_trx_priority(m_wait_lock->trx->mysql_thd) > 0) {

		const trx_t*	victim;

		victim = trx_arbitrate(m_start, m_wait_lock->trx);

		if (victim != NULL) {

			return(victim);
		}
	}

	if (trx_weight_ge(m_wait_lock->trx, m_start)) {

		/* The joining transaction is 'smaller',
		choose it as the victim and roll it back. */

		return(m_start);
	}

	return(m_wait_lock->trx);
}

/** Looks iteratively for a deadlock. Note: the joining transaction may
have been granted its lock by the deadlock checks.
@return 0 if no deadlock else the victim transaction instance.*/
const trx_t*
DeadlockChecker::search()
{
	ut_ad(lock_mutex_own());
	ut_ad(!trx_mutex_own(m_start));

	ut_ad(m_start != NULL);
	ut_ad(m_wait_lock != NULL);
	check_trx_state(m_wait_lock->trx);
	ut_ad(m_mark_start <= s_lock_mark_counter);

	/* Look at the locks ahead of wait_lock in the lock queue. */
	ulint		heap_no;
	const lock_t*	lock = get_first_lock(&heap_no);

	for (;;) {

		/* We should never visit the same sub-tree more than once. */
		ut_ad(lock == NULL || !is_visited(lock));

		while (m_n_elems > 0 && lock == NULL) {

			/* Restore previous search state. */

			pop(lock, heap_no);

			lock = get_next_lock(lock, heap_no);
		}

		if (lock == NULL) {
			break;
		} else if (lock == m_wait_lock) {

			/* We can mark this subtree as searched */
			ut_ad(lock->trx->lock.deadlock_mark <= m_mark_start);

			lock->trx->lock.deadlock_mark = ++s_lock_mark_counter;

			/* We are not prepared for an overflow. This 64-bit
			counter should never wrap around. At 10^9 increments
			per second, it would take 10^3 years of uptime. */

			ut_ad(s_lock_mark_counter > 0);

			/* Backtrack */
			lock = NULL;

		} else if (!lock_has_to_wait(m_wait_lock, lock)) {

			/* No conflict, next lock */
			lock = get_next_lock(lock, heap_no);

		} else if (lock->trx == m_start) {

			/* Found a cycle. */

			notify(lock);

			return(select_victim());

		} else if (is_too_deep()) {

			const trx_t*	victim_trx;

			/* Search too deep to continue. */

			m_too_deep = true;

			/* Select the transaction to rollback */

			victim_trx = trx_arbitrate(m_start, m_wait_lock->trx);

			if (victim_trx == NULL || victim_trx == m_start) {

				return(m_start);
			}

			return(m_wait_lock->trx);

		} else if (lock->trx->lock.que_state == TRX_QUE_LOCK_WAIT) {

			/* Another trx ahead has requested a lock in an
			incompatible mode, and is itself waiting for a lock. */

			++m_cost;

			if (!push(lock, heap_no)) {
				m_too_deep = true;
				return(m_start);
			}


			m_wait_lock = lock->trx->lock.wait_lock;

			lock = get_first_lock(&heap_no);

			if (is_visited(lock)) {
				lock = get_next_lock(lock, heap_no);
			}

		} else {
			lock = get_next_lock(lock, heap_no);
		}
	}

	ut_a(lock == NULL && m_n_elems == 0);

	/* No deadlock found. */
	return(0);
}

/** Print info about transaction that was rolled back.
@param trx transaction rolled back
@param lock lock trx wants */
void
DeadlockChecker::rollback_print(const trx_t*	trx, const lock_t* lock)
{
	ut_ad(lock_mutex_own());

	/* If the lock search exceeds the max step
	or the max depth, the current trx will be
	the victim. Print its information. */
	start_print();

	print("TOO DEEP OR LONG SEARCH IN THE LOCK TABLE"
	      " WAITS-FOR GRAPH, WE WILL ROLL BACK"
	      " FOLLOWING TRANSACTION \n\n"
	      "*** TRANSACTION:\n");

	print(trx, 3000);

	print("*** WAITING FOR THIS LOCK TO BE GRANTED:\n");

	print(lock);
}

/** Rollback transaction selected as the victim. */
void
DeadlockChecker::trx_rollback()
{
	ut_ad(lock_mutex_own());

	trx_t*	trx = m_wait_lock->trx;

	print("*** WE ROLL BACK TRANSACTION (1)\n");

	trx_mutex_enter(trx);

	trx->lock.was_chosen_as_deadlock_victim = true;

	lock_cancel_waiting_and_release(trx->lock.wait_lock);

	trx_mutex_exit(trx);
}

/** Checks if a joining lock request results in a deadlock. If a deadlock is
found this function will resolve the deadlock by choosing a victim transaction
and rolling it back. It will attempt to resolve all deadlocks. The returned
transaction id will be the joining transaction instance or NULL if some other
transaction was chosen as a victim and rolled back or no deadlock found.

@param lock lock the transaction is requesting
@param trx transaction requesting the lock

@return transaction instanace chosen as victim or 0 */
const trx_t*
DeadlockChecker::check_and_resolve(const lock_t* lock, const trx_t* trx)
{
	ut_ad(lock_mutex_own());
	check_trx_state(trx);
	ut_ad(!srv_read_only_mode);

	const trx_t*	victim_trx;

	/* Try and resolve as many deadlocks as possible. */
	do {
		DeadlockChecker	checker(trx, lock, s_lock_mark_counter);

		victim_trx = checker.search();

		/* Search too deep, we rollback the joining transaction only
		if it is possible to rollback. Otherwise we rollback the
		transaction that is holding the lock that the joining
		transaction wants. */
		if (checker.is_too_deep()) {

			ut_ad(trx == checker.m_start);

			victim_trx = trx_arbitrate(
				trx, checker.m_wait_lock->trx);

			if (victim_trx == NULL) {
				victim_trx = trx;
			}

			rollback_print(victim_trx, lock);

			MONITOR_INC(MONITOR_DEADLOCK);

			break;

		} else if (victim_trx != 0 && victim_trx != trx) {

			ut_ad(victim_trx == checker.m_wait_lock->trx);

			checker.trx_rollback();

			lock_deadlock_found = true;

			MONITOR_INC(MONITOR_DEADLOCK);
		}

	} while (victim_trx != NULL && victim_trx != trx);

	/* If the joining transaction was selected as the victim. */
	if (victim_trx != NULL) {

		print("*** WE ROLL BACK TRANSACTION (2)\n");

		lock_deadlock_found = true;
	}

	return(victim_trx);
}

/**
Allocate cached locks for the transaction.
@param trx		allocate cached record locks for this transaction */
void
lock_trx_alloc_locks(trx_t* trx)
{
	ulint	sz = REC_LOCK_SIZE * REC_LOCK_CACHE;
	byte*	ptr = reinterpret_cast<byte*>(ut_malloc_nokey(sz));

	/* We allocate one big chunk and then distribute it among
	the rest of the elements. The allocated chunk pointer is always
	at index 0. */

	for (ulint i = 0; i < REC_LOCK_CACHE; ++i, ptr += REC_LOCK_SIZE) {
		trx->lock.rec_pool.push_back(
			reinterpret_cast<ib_lock_t*>(ptr));
	}

	sz = TABLE_LOCK_SIZE * TABLE_LOCK_CACHE;
	ptr = reinterpret_cast<byte*>(ut_malloc_nokey(sz));

	for (ulint i = 0; i < TABLE_LOCK_CACHE; ++i, ptr += TABLE_LOCK_SIZE) {
		trx->lock.table_pool.push_back(
			reinterpret_cast<ib_lock_t*>(ptr));
	}

}