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/*-------------------------------------------------------------------------
*
* heapam.c
* heap access method code
*
* Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
*
* IDENTIFICATION
* src/backend/access/heap/heapam.c
*
*
* INTERFACE ROUTINES
* relation_open - open any relation by relation OID
* relation_openrv - open any relation specified by a RangeVar
* relation_close - close any relation
* heap_open - open a heap relation by relation OID
* heap_openrv - open a heap relation specified by a RangeVar
* heap_close - (now just a macro for relation_close)
* heap_beginscan - begin relation scan
* heap_rescan - restart a relation scan
* heap_endscan - end relation scan
* heap_getnext - retrieve next tuple in scan
* heap_fetch - retrieve tuple with given tid
* heap_insert - insert tuple into a relation
* heap_multi_insert - insert multiple tuples into a relation
* heap_delete - delete a tuple from a relation
* heap_update - replace a tuple in a relation with another tuple
* heap_markpos - mark scan position
* heap_restrpos - restore position to marked location
* heap_sync - sync heap, for when no WAL has been written
*
* NOTES
* This file contains the heap_ routines which implement
* the POSTGRES heap access method used for all POSTGRES
* relations.
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/heapam.h"
#include "access/hio.h"
#include "access/multixact.h"
#include "access/relscan.h"
#include "access/sysattr.h"
#include "access/transam.h"
#include "access/tuptoaster.h"
#include "access/valid.h"
#include "access/visibilitymap.h"
#include "access/xact.h"
#include "access/xlogutils.h"
#include "catalog/catalog.h"
#include "catalog/namespace.h"
#include "miscadmin.h"
#include "pgstat.h"
#include "storage/bufmgr.h"
#include "storage/freespace.h"
#include "storage/lmgr.h"
#include "storage/predicate.h"
#include "storage/procarray.h"
#include "storage/smgr.h"
#include "storage/standby.h"
#include "utils/datum.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/relcache.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
#include "utils/tqual.h"
/* GUC variable */
bool synchronize_seqscans = true;
static HeapScanDesc heap_beginscan_internal(Relation relation,
Snapshot snapshot,
int nkeys, ScanKey key,
bool allow_strat, bool allow_sync,
bool is_bitmapscan);
static HeapTuple heap_prepare_insert(Relation relation, HeapTuple tup,
TransactionId xid, CommandId cid, int options);
static XLogRecPtr log_heap_update(Relation reln, Buffer oldbuf,
ItemPointerData from, Buffer newbuf, HeapTuple newtup,
bool all_visible_cleared, bool new_all_visible_cleared);
static bool HeapSatisfiesHOTUpdate(Relation relation, Bitmapset *hot_attrs,
HeapTuple oldtup, HeapTuple newtup);
/* ----------------------------------------------------------------
* heap support routines
* ----------------------------------------------------------------
*/
/* ----------------
* initscan - scan code common to heap_beginscan and heap_rescan
* ----------------
*/
static void
initscan(HeapScanDesc scan, ScanKey key, bool is_rescan)
{
bool allow_strat;
bool allow_sync;
/*
* Determine the number of blocks we have to scan.
*
* It is sufficient to do this once at scan start, since any tuples added
* while the scan is in progress will be invisible to my snapshot anyway.
* (That is not true when using a non-MVCC snapshot. However, we couldn't
* guarantee to return tuples added after scan start anyway, since they
* might go into pages we already scanned. To guarantee consistent
* results for a non-MVCC snapshot, the caller must hold some higher-level
* lock that ensures the interesting tuple(s) won't change.)
*/
scan->rs_nblocks = RelationGetNumberOfBlocks(scan->rs_rd);
/*
* If the table is large relative to NBuffers, use a bulk-read access
* strategy and enable synchronized scanning (see syncscan.c). Although
* the thresholds for these features could be different, we make them the
* same so that there are only two behaviors to tune rather than four.
* (However, some callers need to be able to disable one or both of these
* behaviors, independently of the size of the table; also there is a GUC
* variable that can disable synchronized scanning.)
*
* During a rescan, don't make a new strategy object if we don't have to.
*/
if (!RelationUsesLocalBuffers(scan->rs_rd) &&
scan->rs_nblocks > NBuffers / 4)
{
allow_strat = scan->rs_allow_strat;
allow_sync = scan->rs_allow_sync;
}
else
allow_strat = allow_sync = false;
if (allow_strat)
{
if (scan->rs_strategy == NULL)
scan->rs_strategy = GetAccessStrategy(BAS_BULKREAD);
}
else
{
if (scan->rs_strategy != NULL)
FreeAccessStrategy(scan->rs_strategy);
scan->rs_strategy = NULL;
}
if (is_rescan)
{
/*
* If rescan, keep the previous startblock setting so that rewinding a
* cursor doesn't generate surprising results. Reset the syncscan
* setting, though.
*/
scan->rs_syncscan = (allow_sync && synchronize_seqscans);
}
else if (allow_sync && synchronize_seqscans)
{
scan->rs_syncscan = true;
scan->rs_startblock = ss_get_location(scan->rs_rd, scan->rs_nblocks);
}
else
{
scan->rs_syncscan = false;
scan->rs_startblock = 0;
}
scan->rs_inited = false;
scan->rs_ctup.t_data = NULL;
ItemPointerSetInvalid(&scan->rs_ctup.t_self);
scan->rs_cbuf = InvalidBuffer;
scan->rs_cblock = InvalidBlockNumber;
/* we don't have a marked position... */
ItemPointerSetInvalid(&(scan->rs_mctid));
/* page-at-a-time fields are always invalid when not rs_inited */
/*
* copy the scan key, if appropriate
*/
if (key != NULL)
memcpy(scan->rs_key, key, scan->rs_nkeys * sizeof(ScanKeyData));
/*
* Currently, we don't have a stats counter for bitmap heap scans (but the
* underlying bitmap index scans will be counted).
*/
if (!scan->rs_bitmapscan)
pgstat_count_heap_scan(scan->rs_rd);
}
/*
* heapgetpage - subroutine for heapgettup()
*
* This routine reads and pins the specified page of the relation.
* In page-at-a-time mode it performs additional work, namely determining
* which tuples on the page are visible.
*/
static void
heapgetpage(HeapScanDesc scan, BlockNumber page)
{
Buffer buffer;
Snapshot snapshot;
Page dp;
int lines;
int ntup;
OffsetNumber lineoff;
ItemId lpp;
bool all_visible;
Assert(page < scan->rs_nblocks);
/* release previous scan buffer, if any */
if (BufferIsValid(scan->rs_cbuf))
{
ReleaseBuffer(scan->rs_cbuf);
scan->rs_cbuf = InvalidBuffer;
}
/* read page using selected strategy */
scan->rs_cbuf = ReadBufferExtended(scan->rs_rd, MAIN_FORKNUM, page,
RBM_NORMAL, scan->rs_strategy);
scan->rs_cblock = page;
if (!scan->rs_pageatatime)
return;
buffer = scan->rs_cbuf;
snapshot = scan->rs_snapshot;
/*
* Prune and repair fragmentation for the whole page, if possible.
*/
Assert(TransactionIdIsValid(RecentGlobalXmin));
heap_page_prune_opt(scan->rs_rd, buffer, RecentGlobalXmin);
/*
* We must hold share lock on the buffer content while examining tuple
* visibility. Afterwards, however, the tuples we have found to be
* visible are guaranteed good as long as we hold the buffer pin.
*/
LockBuffer(buffer, BUFFER_LOCK_SHARE);
dp = (Page) BufferGetPage(buffer);
lines = PageGetMaxOffsetNumber(dp);
ntup = 0;
/*
* If the all-visible flag indicates that all tuples on the page are
* visible to everyone, we can skip the per-tuple visibility tests. But
* not in hot standby mode. A tuple that's already visible to all
* transactions in the master might still be invisible to a read-only
* transaction in the standby.
*/
all_visible = PageIsAllVisible(dp) && !snapshot->takenDuringRecovery;
for (lineoff = FirstOffsetNumber, lpp = PageGetItemId(dp, lineoff);
lineoff <= lines;
lineoff++, lpp++)
{
if (ItemIdIsNormal(lpp))
{
HeapTupleData loctup;
bool valid;
loctup.t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp);
loctup.t_len = ItemIdGetLength(lpp);
ItemPointerSet(&(loctup.t_self), page, lineoff);
if (all_visible)
valid = true;
else
valid = HeapTupleSatisfiesVisibility(&loctup, snapshot, buffer);
CheckForSerializableConflictOut(valid, scan->rs_rd, &loctup,
buffer, snapshot);
if (valid)
scan->rs_vistuples[ntup++] = lineoff;
}
}
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
Assert(ntup <= MaxHeapTuplesPerPage);
scan->rs_ntuples = ntup;
}
/* ----------------
* heapgettup - fetch next heap tuple
*
* Initialize the scan if not already done; then advance to the next
* tuple as indicated by "dir"; return the next tuple in scan->rs_ctup,
* or set scan->rs_ctup.t_data = NULL if no more tuples.
*
* dir == NoMovementScanDirection means "re-fetch the tuple indicated
* by scan->rs_ctup".
*
* Note: the reason nkeys/key are passed separately, even though they are
* kept in the scan descriptor, is that the caller may not want us to check
* the scankeys.
*
* Note: when we fall off the end of the scan in either direction, we
* reset rs_inited. This means that a further request with the same
* scan direction will restart the scan, which is a bit odd, but a
* request with the opposite scan direction will start a fresh scan
* in the proper direction. The latter is required behavior for cursors,
* while the former case is generally undefined behavior in Postgres
* so we don't care too much.
* ----------------
*/
static void
heapgettup(HeapScanDesc scan,
ScanDirection dir,
int nkeys,
ScanKey key)
{
HeapTuple tuple = &(scan->rs_ctup);
Snapshot snapshot = scan->rs_snapshot;
bool backward = ScanDirectionIsBackward(dir);
BlockNumber page;
bool finished;
Page dp;
int lines;
OffsetNumber lineoff;
int linesleft;
ItemId lpp;
/*
* calculate next starting lineoff, given scan direction
*/
if (ScanDirectionIsForward(dir))
{
if (!scan->rs_inited)
{
/*
* return null immediately if relation is empty
*/
if (scan->rs_nblocks == 0)
{
Assert(!BufferIsValid(scan->rs_cbuf));
tuple->t_data = NULL;
return;
}
page = scan->rs_startblock; /* first page */
heapgetpage(scan, page);
lineoff = FirstOffsetNumber; /* first offnum */
scan->rs_inited = true;
}
else
{
/* continue from previously returned page/tuple */
page = scan->rs_cblock; /* current page */
lineoff = /* next offnum */
OffsetNumberNext(ItemPointerGetOffsetNumber(&(tuple->t_self)));
}
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
dp = (Page) BufferGetPage(scan->rs_cbuf);
lines = PageGetMaxOffsetNumber(dp);
/* page and lineoff now reference the physically next tid */
linesleft = lines - lineoff + 1;
}
else if (backward)
{
if (!scan->rs_inited)
{
/*
* return null immediately if relation is empty
*/
if (scan->rs_nblocks == 0)
{
Assert(!BufferIsValid(scan->rs_cbuf));
tuple->t_data = NULL;
return;
}
/*
* Disable reporting to syncscan logic in a backwards scan; it's
* not very likely anyone else is doing the same thing at the same
* time, and much more likely that we'll just bollix things for
* forward scanners.
*/
scan->rs_syncscan = false;
/* start from last page of the scan */
if (scan->rs_startblock > 0)
page = scan->rs_startblock - 1;
else
page = scan->rs_nblocks - 1;
heapgetpage(scan, page);
}
else
{
/* continue from previously returned page/tuple */
page = scan->rs_cblock; /* current page */
}
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
dp = (Page) BufferGetPage(scan->rs_cbuf);
lines = PageGetMaxOffsetNumber(dp);
if (!scan->rs_inited)
{
lineoff = lines; /* final offnum */
scan->rs_inited = true;
}
else
{
lineoff = /* previous offnum */
OffsetNumberPrev(ItemPointerGetOffsetNumber(&(tuple->t_self)));
}
/* page and lineoff now reference the physically previous tid */
linesleft = lineoff;
}
else
{
/*
* ``no movement'' scan direction: refetch prior tuple
*/
if (!scan->rs_inited)
{
Assert(!BufferIsValid(scan->rs_cbuf));
tuple->t_data = NULL;
return;
}
page = ItemPointerGetBlockNumber(&(tuple->t_self));
if (page != scan->rs_cblock)
heapgetpage(scan, page);
/* Since the tuple was previously fetched, needn't lock page here */
dp = (Page) BufferGetPage(scan->rs_cbuf);
lineoff = ItemPointerGetOffsetNumber(&(tuple->t_self));
lpp = PageGetItemId(dp, lineoff);
Assert(ItemIdIsNormal(lpp));
tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp);
tuple->t_len = ItemIdGetLength(lpp);
return;
}
/*
* advance the scan until we find a qualifying tuple or run out of stuff
* to scan
*/
lpp = PageGetItemId(dp, lineoff);
for (;;)
{
while (linesleft > 0)
{
if (ItemIdIsNormal(lpp))
{
bool valid;
tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp);
tuple->t_len = ItemIdGetLength(lpp);
ItemPointerSet(&(tuple->t_self), page, lineoff);
/*
* if current tuple qualifies, return it.
*/
valid = HeapTupleSatisfiesVisibility(tuple,
snapshot,
scan->rs_cbuf);
CheckForSerializableConflictOut(valid, scan->rs_rd, tuple,
scan->rs_cbuf, snapshot);
if (valid && key != NULL)
HeapKeyTest(tuple, RelationGetDescr(scan->rs_rd),
nkeys, key, valid);
if (valid)
{
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
return;
}
}
/*
* otherwise move to the next item on the page
*/
--linesleft;
if (backward)
{
--lpp; /* move back in this page's ItemId array */
--lineoff;
}
else
{
++lpp; /* move forward in this page's ItemId array */
++lineoff;
}
}
/*
* if we get here, it means we've exhausted the items on this page and
* it's time to move to the next.
*/
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_UNLOCK);
/*
* advance to next/prior page and detect end of scan
*/
if (backward)
{
finished = (page == scan->rs_startblock);
if (page == 0)
page = scan->rs_nblocks;
page--;
}
else
{
page++;
if (page >= scan->rs_nblocks)
page = 0;
finished = (page == scan->rs_startblock);
/*
* Report our new scan position for synchronization purposes. We
* don't do that when moving backwards, however. That would just
* mess up any other forward-moving scanners.
*
* Note: we do this before checking for end of scan so that the
* final state of the position hint is back at the start of the
* rel. That's not strictly necessary, but otherwise when you run
* the same query multiple times the starting position would shift
* a little bit backwards on every invocation, which is confusing.
* We don't guarantee any specific ordering in general, though.
*/
if (scan->rs_syncscan)
ss_report_location(scan->rs_rd, page);
}
/*
* return NULL if we've exhausted all the pages
*/
if (finished)
{
if (BufferIsValid(scan->rs_cbuf))
ReleaseBuffer(scan->rs_cbuf);
scan->rs_cbuf = InvalidBuffer;
scan->rs_cblock = InvalidBlockNumber;
tuple->t_data = NULL;
scan->rs_inited = false;
return;
}
heapgetpage(scan, page);
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
dp = (Page) BufferGetPage(scan->rs_cbuf);
lines = PageGetMaxOffsetNumber((Page) dp);
linesleft = lines;
if (backward)
{
lineoff = lines;
lpp = PageGetItemId(dp, lines);
}
else
{
lineoff = FirstOffsetNumber;
lpp = PageGetItemId(dp, FirstOffsetNumber);
}
}
}
/* ----------------
* heapgettup_pagemode - fetch next heap tuple in page-at-a-time mode
*
* Same API as heapgettup, but used in page-at-a-time mode
*
* The internal logic is much the same as heapgettup's too, but there are some
* differences: we do not take the buffer content lock (that only needs to
* happen inside heapgetpage), and we iterate through just the tuples listed
* in rs_vistuples[] rather than all tuples on the page. Notice that
* lineindex is 0-based, where the corresponding loop variable lineoff in
* heapgettup is 1-based.
* ----------------
*/
static void
heapgettup_pagemode(HeapScanDesc scan,
ScanDirection dir,
int nkeys,
ScanKey key)
{
HeapTuple tuple = &(scan->rs_ctup);
bool backward = ScanDirectionIsBackward(dir);
BlockNumber page;
bool finished;
Page dp;
int lines;
int lineindex;
OffsetNumber lineoff;
int linesleft;
ItemId lpp;
/*
* calculate next starting lineindex, given scan direction
*/
if (ScanDirectionIsForward(dir))
{
if (!scan->rs_inited)
{
/*
* return null immediately if relation is empty
*/
if (scan->rs_nblocks == 0)
{
Assert(!BufferIsValid(scan->rs_cbuf));
tuple->t_data = NULL;
return;
}
page = scan->rs_startblock; /* first page */
heapgetpage(scan, page);
lineindex = 0;
scan->rs_inited = true;
}
else
{
/* continue from previously returned page/tuple */
page = scan->rs_cblock; /* current page */
lineindex = scan->rs_cindex + 1;
}
dp = (Page) BufferGetPage(scan->rs_cbuf);
lines = scan->rs_ntuples;
/* page and lineindex now reference the next visible tid */
linesleft = lines - lineindex;
}
else if (backward)
{
if (!scan->rs_inited)
{
/*
* return null immediately if relation is empty
*/
if (scan->rs_nblocks == 0)
{
Assert(!BufferIsValid(scan->rs_cbuf));
tuple->t_data = NULL;
return;
}
/*
* Disable reporting to syncscan logic in a backwards scan; it's
* not very likely anyone else is doing the same thing at the same
* time, and much more likely that we'll just bollix things for
* forward scanners.
*/
scan->rs_syncscan = false;
/* start from last page of the scan */
if (scan->rs_startblock > 0)
page = scan->rs_startblock - 1;
else
page = scan->rs_nblocks - 1;
heapgetpage(scan, page);
}
else
{
/* continue from previously returned page/tuple */
page = scan->rs_cblock; /* current page */
}
dp = (Page) BufferGetPage(scan->rs_cbuf);
lines = scan->rs_ntuples;
if (!scan->rs_inited)
{
lineindex = lines - 1;
scan->rs_inited = true;
}
else
{
lineindex = scan->rs_cindex - 1;
}
/* page and lineindex now reference the previous visible tid */
linesleft = lineindex + 1;
}
else
{
/*
* ``no movement'' scan direction: refetch prior tuple
*/
if (!scan->rs_inited)
{
Assert(!BufferIsValid(scan->rs_cbuf));
tuple->t_data = NULL;
return;
}
page = ItemPointerGetBlockNumber(&(tuple->t_self));
if (page != scan->rs_cblock)
heapgetpage(scan, page);
/* Since the tuple was previously fetched, needn't lock page here */
dp = (Page) BufferGetPage(scan->rs_cbuf);
lineoff = ItemPointerGetOffsetNumber(&(tuple->t_self));
lpp = PageGetItemId(dp, lineoff);
Assert(ItemIdIsNormal(lpp));
tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp);
tuple->t_len = ItemIdGetLength(lpp);
/* check that rs_cindex is in sync */
Assert(scan->rs_cindex < scan->rs_ntuples);
Assert(lineoff == scan->rs_vistuples[scan->rs_cindex]);
return;
}
/*
* advance the scan until we find a qualifying tuple or run out of stuff
* to scan
*/
for (;;)
{
while (linesleft > 0)
{
lineoff = scan->rs_vistuples[lineindex];
lpp = PageGetItemId(dp, lineoff);
Assert(ItemIdIsNormal(lpp));
tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp);
tuple->t_len = ItemIdGetLength(lpp);
ItemPointerSet(&(tuple->t_self), page, lineoff);
/*
* if current tuple qualifies, return it.
*/
if (key != NULL)
{
bool valid;
HeapKeyTest(tuple, RelationGetDescr(scan->rs_rd),
nkeys, key, valid);
if (valid)
{
scan->rs_cindex = lineindex;
return;
}
}
else
{
scan->rs_cindex = lineindex;
return;
}
/*
* otherwise move to the next item on the page
*/
--linesleft;
if (backward)
--lineindex;
else
++lineindex;
}
/*
* if we get here, it means we've exhausted the items on this page and
* it's time to move to the next.
*/
if (backward)
{
finished = (page == scan->rs_startblock);
if (page == 0)
page = scan->rs_nblocks;
page--;
}
else
{
page++;
if (page >= scan->rs_nblocks)
page = 0;
finished = (page == scan->rs_startblock);
/*
* Report our new scan position for synchronization purposes. We
* don't do that when moving backwards, however. That would just
* mess up any other forward-moving scanners.
*
* Note: we do this before checking for end of scan so that the
* final state of the position hint is back at the start of the
* rel. That's not strictly necessary, but otherwise when you run
* the same query multiple times the starting position would shift
* a little bit backwards on every invocation, which is confusing.
* We don't guarantee any specific ordering in general, though.
*/
if (scan->rs_syncscan)
ss_report_location(scan->rs_rd, page);
}
/*
* return NULL if we've exhausted all the pages
*/
if (finished)
{
if (BufferIsValid(scan->rs_cbuf))
ReleaseBuffer(scan->rs_cbuf);
scan->rs_cbuf = InvalidBuffer;
scan->rs_cblock = InvalidBlockNumber;
tuple->t_data = NULL;
scan->rs_inited = false;
return;
}
heapgetpage(scan, page);
dp = (Page) BufferGetPage(scan->rs_cbuf);
lines = scan->rs_ntuples;
linesleft = lines;
if (backward)
lineindex = lines - 1;
else
lineindex = 0;
}
}
#if defined(DISABLE_COMPLEX_MACRO)
/*
* This is formatted so oddly so that the correspondence to the macro
* definition in access/htup.h is maintained.
*/
Datum
fastgetattr(HeapTuple tup, int attnum, TupleDesc tupleDesc,
bool *isnull)
{
return (
(attnum) > 0 ?
(
(*(isnull) = false),
HeapTupleNoNulls(tup) ?
(
(tupleDesc)->attrs[(attnum) - 1]->attcacheoff >= 0 ?
(
fetchatt((tupleDesc)->attrs[(attnum) - 1],
(char *) (tup)->t_data + (tup)->t_data->t_hoff +
(tupleDesc)->attrs[(attnum) - 1]->attcacheoff)
)
:
nocachegetattr((tup), (attnum), (tupleDesc))
)
:
(
att_isnull((attnum) - 1, (tup)->t_data->t_bits) ?
(
(*(isnull) = true),
(Datum) NULL
)
:
(
nocachegetattr((tup), (attnum), (tupleDesc))
)
)
)
:
(
(Datum) NULL
)
);
}
#endif /* defined(DISABLE_COMPLEX_MACRO) */
/* ----------------------------------------------------------------
* heap access method interface
* ----------------------------------------------------------------
*/
/* ----------------
* relation_open - open any relation by relation OID
*
* If lockmode is not "NoLock", the specified kind of lock is
* obtained on the relation. (Generally, NoLock should only be
* used if the caller knows it has some appropriate lock on the
* relation already.)
*
* An error is raised if the relation does not exist.
*
* NB: a "relation" is anything with a pg_class entry. The caller is
* expected to check whether the relkind is something it can handle.
* ----------------
*/
Relation
relation_open(Oid relationId, LOCKMODE lockmode)
{
Relation r;
Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
/* Get the lock before trying to open the relcache entry */
if (lockmode != NoLock)
LockRelationOid(relationId, lockmode);
/* The relcache does all the real work... */
r = RelationIdGetRelation(relationId);
if (!RelationIsValid(r))
elog(ERROR, "could not open relation with OID %u", relationId);
/* Make note that we've accessed a temporary relation */
if (RelationUsesLocalBuffers(r))
MyXactAccessedTempRel = true;
pgstat_initstats(r);
return r;
}
/* ----------------
* try_relation_open - open any relation by relation OID
*
* Same as relation_open, except return NULL instead of failing
* if the relation does not exist.
* ----------------
*/
Relation
try_relation_open(Oid relationId, LOCKMODE lockmode)
{
Relation r;
Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
/* Get the lock first */
if (lockmode != NoLock)
LockRelationOid(relationId, lockmode);
/*
* Now that we have the lock, probe to see if the relation really exists
* or not.
*/
if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(relationId)))
{
/* Release useless lock */
if (lockmode != NoLock)
UnlockRelationOid(relationId, lockmode);
return NULL;
}
/* Should be safe to do a relcache load */
r = RelationIdGetRelation(relationId);
if (!RelationIsValid(r))
elog(ERROR, "could not open relation with OID %u", relationId);
/* Make note that we've accessed a temporary relation */
if (RelationUsesLocalBuffers(r))
MyXactAccessedTempRel = true;
pgstat_initstats(r);
return r;
}
/* ----------------
* relation_openrv - open any relation specified by a RangeVar
*
* Same as relation_open, but the relation is specified by a RangeVar.
* ----------------
*/
Relation
relation_openrv(const RangeVar *relation, LOCKMODE lockmode)
{
Oid relOid;
/* Look up and lock the appropriate relation using namespace search */
relOid = RangeVarGetRelid(relation, lockmode, false);
/* Let relation_open do the rest */
return relation_open(relOid, NoLock);
}
/* ----------------
* relation_openrv_extended - open any relation specified by a RangeVar
*
* Same as relation_openrv, but with an additional missing_ok argument
* allowing a NULL return rather than an error if the relation is not
* found. (Note that some other causes, such as permissions problems,
* will still result in an ereport.)
* ----------------
*/
Relation
relation_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
bool missing_ok)
{
Oid relOid;
/* Look up and lock the appropriate relation using namespace search */
relOid = RangeVarGetRelid(relation, lockmode, missing_ok);
/* Return NULL on not-found */
if (!OidIsValid(relOid))
return NULL;
/* Let relation_open do the rest */
return relation_open(relOid, NoLock);
}
/* ----------------
* relation_close - close any relation
*
* If lockmode is not "NoLock", we then release the specified lock.
*
* Note that it is often sensible to hold a lock beyond relation_close;
* in that case, the lock is released automatically at xact end.
* ----------------
*/
void
relation_close(Relation relation, LOCKMODE lockmode)
{
LockRelId relid = relation->rd_lockInfo.lockRelId;
Assert(lockmode >= NoLock && lockmode < MAX_LOCKMODES);
/* The relcache does the real work... */
RelationClose(relation);
if (lockmode != NoLock)
UnlockRelationId(&relid, lockmode);
}
/* ----------------
* heap_open - open a heap relation by relation OID
*
* This is essentially relation_open plus check that the relation
* is not an index nor a composite type. (The caller should also
* check that it's not a view or foreign table before assuming it has
* storage.)
* ----------------
*/
Relation
heap_open(Oid relationId, LOCKMODE lockmode)
{
Relation r;
r = relation_open(relationId, lockmode);
if (r->rd_rel->relkind == RELKIND_INDEX)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("\"%s\" is an index",
RelationGetRelationName(r))));
else if (r->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("\"%s\" is a composite type",
RelationGetRelationName(r))));
return r;
}
/* ----------------
* heap_openrv - open a heap relation specified
* by a RangeVar node
*
* As above, but relation is specified by a RangeVar.
* ----------------
*/
Relation
heap_openrv(const RangeVar *relation, LOCKMODE lockmode)
{
Relation r;
r = relation_openrv(relation, lockmode);
if (r->rd_rel->relkind == RELKIND_INDEX)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("\"%s\" is an index",
RelationGetRelationName(r))));
else if (r->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("\"%s\" is a composite type",
RelationGetRelationName(r))));
return r;
}
/* ----------------
* heap_openrv_extended - open a heap relation specified
* by a RangeVar node
*
* As above, but optionally return NULL instead of failing for
* relation-not-found.
* ----------------
*/
Relation
heap_openrv_extended(const RangeVar *relation, LOCKMODE lockmode,
bool missing_ok)
{
Relation r;
r = relation_openrv_extended(relation, lockmode, missing_ok);
if (r)
{
if (r->rd_rel->relkind == RELKIND_INDEX)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("\"%s\" is an index",
RelationGetRelationName(r))));
else if (r->rd_rel->relkind == RELKIND_COMPOSITE_TYPE)
ereport(ERROR,
(errcode(ERRCODE_WRONG_OBJECT_TYPE),
errmsg("\"%s\" is a composite type",
RelationGetRelationName(r))));
}
return r;
}
/* ----------------
* heap_beginscan - begin relation scan
*
* heap_beginscan_strat offers an extended API that lets the caller control
* whether a nondefault buffer access strategy can be used, and whether
* syncscan can be chosen (possibly resulting in the scan not starting from
* block zero). Both of these default to TRUE with plain heap_beginscan.
*
* heap_beginscan_bm is an alternative entry point for setting up a
* HeapScanDesc for a bitmap heap scan. Although that scan technology is
* really quite unlike a standard seqscan, there is just enough commonality
* to make it worth using the same data structure.
* ----------------
*/
HeapScanDesc
heap_beginscan(Relation relation, Snapshot snapshot,
int nkeys, ScanKey key)
{
return heap_beginscan_internal(relation, snapshot, nkeys, key,
true, true, false);
}
HeapScanDesc
heap_beginscan_strat(Relation relation, Snapshot snapshot,
int nkeys, ScanKey key,
bool allow_strat, bool allow_sync)
{
return heap_beginscan_internal(relation, snapshot, nkeys, key,
allow_strat, allow_sync, false);
}
HeapScanDesc
heap_beginscan_bm(Relation relation, Snapshot snapshot,
int nkeys, ScanKey key)
{
return heap_beginscan_internal(relation, snapshot, nkeys, key,
false, false, true);
}
static HeapScanDesc
heap_beginscan_internal(Relation relation, Snapshot snapshot,
int nkeys, ScanKey key,
bool allow_strat, bool allow_sync,
bool is_bitmapscan)
{
HeapScanDesc scan;
/*
* increment relation ref count while scanning relation
*
* This is just to make really sure the relcache entry won't go away while
* the scan has a pointer to it. Caller should be holding the rel open
* anyway, so this is redundant in all normal scenarios...
*/
RelationIncrementReferenceCount(relation);
/*
* allocate and initialize scan descriptor
*/
scan = (HeapScanDesc) palloc(sizeof(HeapScanDescData));
scan->rs_rd = relation;
scan->rs_snapshot = snapshot;
scan->rs_nkeys = nkeys;
scan->rs_bitmapscan = is_bitmapscan;
scan->rs_strategy = NULL; /* set in initscan */
scan->rs_allow_strat = allow_strat;
scan->rs_allow_sync = allow_sync;
/*
* we can use page-at-a-time mode if it's an MVCC-safe snapshot
*/
scan->rs_pageatatime = IsMVCCSnapshot(snapshot);
/*
* For a seqscan in a serializable transaction, acquire a predicate lock
* on the entire relation. This is required not only to lock all the
* matching tuples, but also to conflict with new insertions into the
* table. In an indexscan, we take page locks on the index pages covering
* the range specified in the scan qual, but in a heap scan there is
* nothing more fine-grained to lock. A bitmap scan is a different story,
* there we have already scanned the index and locked the index pages
* covering the predicate. But in that case we still have to lock any
* matching heap tuples.
*/
if (!is_bitmapscan)
PredicateLockRelation(relation, snapshot);
/* we only need to set this up once */
scan->rs_ctup.t_tableOid = RelationGetRelid(relation);
/*
* we do this here instead of in initscan() because heap_rescan also calls
* initscan() and we don't want to allocate memory again
*/
if (nkeys > 0)
scan->rs_key = (ScanKey) palloc(sizeof(ScanKeyData) * nkeys);
else
scan->rs_key = NULL;
initscan(scan, key, false);
return scan;
}
/* ----------------
* heap_rescan - restart a relation scan
* ----------------
*/
void
heap_rescan(HeapScanDesc scan,
ScanKey key)
{
/*
* unpin scan buffers
*/
if (BufferIsValid(scan->rs_cbuf))
ReleaseBuffer(scan->rs_cbuf);
/*
* reinitialize scan descriptor
*/
initscan(scan, key, true);
}
/* ----------------
* heap_endscan - end relation scan
*
* See how to integrate with index scans.
* Check handling if reldesc caching.
* ----------------
*/
void
heap_endscan(HeapScanDesc scan)
{
/* Note: no locking manipulations needed */
/*
* unpin scan buffers
*/
if (BufferIsValid(scan->rs_cbuf))
ReleaseBuffer(scan->rs_cbuf);
/*
* decrement relation reference count and free scan descriptor storage
*/
RelationDecrementReferenceCount(scan->rs_rd);
if (scan->rs_key)
pfree(scan->rs_key);
if (scan->rs_strategy != NULL)
FreeAccessStrategy(scan->rs_strategy);
pfree(scan);
}
/* ----------------
* heap_getnext - retrieve next tuple in scan
*
* Fix to work with index relations.
* We don't return the buffer anymore, but you can get it from the
* returned HeapTuple.
* ----------------
*/
#ifdef HEAPDEBUGALL
#define HEAPDEBUG_1 \
elog(DEBUG2, "heap_getnext([%s,nkeys=%d],dir=%d) called", \
RelationGetRelationName(scan->rs_rd), scan->rs_nkeys, (int) direction)
#define HEAPDEBUG_2 \
elog(DEBUG2, "heap_getnext returning EOS")
#define HEAPDEBUG_3 \
elog(DEBUG2, "heap_getnext returning tuple")
#else
#define HEAPDEBUG_1
#define HEAPDEBUG_2
#define HEAPDEBUG_3
#endif /* !defined(HEAPDEBUGALL) */
HeapTuple
heap_getnext(HeapScanDesc scan, ScanDirection direction)
{
/* Note: no locking manipulations needed */
HEAPDEBUG_1; /* heap_getnext( info ) */
if (scan->rs_pageatatime)
heapgettup_pagemode(scan, direction,
scan->rs_nkeys, scan->rs_key);
else
heapgettup(scan, direction, scan->rs_nkeys, scan->rs_key);
if (scan->rs_ctup.t_data == NULL)
{
HEAPDEBUG_2; /* heap_getnext returning EOS */
return NULL;
}
/*
* if we get here it means we have a new current scan tuple, so point to
* the proper return buffer and return the tuple.
*/
HEAPDEBUG_3; /* heap_getnext returning tuple */
pgstat_count_heap_getnext(scan->rs_rd);
return &(scan->rs_ctup);
}
/*
* heap_fetch - retrieve tuple with given tid
*
* On entry, tuple->t_self is the TID to fetch. We pin the buffer holding
* the tuple, fill in the remaining fields of *tuple, and check the tuple
* against the specified snapshot.
*
* If successful (tuple found and passes snapshot time qual), then *userbuf
* is set to the buffer holding the tuple and TRUE is returned. The caller
* must unpin the buffer when done with the tuple.
*
* If the tuple is not found (ie, item number references a deleted slot),
* then tuple->t_data is set to NULL and FALSE is returned.
*
* If the tuple is found but fails the time qual check, then FALSE is returned
* but tuple->t_data is left pointing to the tuple.
*
* keep_buf determines what is done with the buffer in the FALSE-result cases.
* When the caller specifies keep_buf = true, we retain the pin on the buffer
* and return it in *userbuf (so the caller must eventually unpin it); when
* keep_buf = false, the pin is released and *userbuf is set to InvalidBuffer.
*
* stats_relation is the relation to charge the heap_fetch operation against
* for statistical purposes. (This could be the heap rel itself, an
* associated index, or NULL to not count the fetch at all.)
*
* heap_fetch does not follow HOT chains: only the exact TID requested will
* be fetched.
*
* It is somewhat inconsistent that we ereport() on invalid block number but
* return false on invalid item number. There are a couple of reasons though.
* One is that the caller can relatively easily check the block number for
* validity, but cannot check the item number without reading the page
* himself. Another is that when we are following a t_ctid link, we can be
* reasonably confident that the page number is valid (since VACUUM shouldn't
* truncate off the destination page without having killed the referencing
* tuple first), but the item number might well not be good.
*/
bool
heap_fetch(Relation relation,
Snapshot snapshot,
HeapTuple tuple,
Buffer *userbuf,
bool keep_buf,
Relation stats_relation)
{
ItemPointer tid = &(tuple->t_self);
ItemId lp;
Buffer buffer;
Page page;
OffsetNumber offnum;
bool valid;
/*
* Fetch and pin the appropriate page of the relation.
*/
buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid));
/*
* Need share lock on buffer to examine tuple commit status.
*/
LockBuffer(buffer, BUFFER_LOCK_SHARE);
page = BufferGetPage(buffer);
/*
* We'd better check for out-of-range offnum in case of VACUUM since the
* TID was obtained.
*/
offnum = ItemPointerGetOffsetNumber(tid);
if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(page))
{
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
if (keep_buf)
*userbuf = buffer;
else
{
ReleaseBuffer(buffer);
*userbuf = InvalidBuffer;
}
tuple->t_data = NULL;
return false;
}
/*
* get the item line pointer corresponding to the requested tid
*/
lp = PageGetItemId(page, offnum);
/*
* Must check for deleted tuple.
*/
if (!ItemIdIsNormal(lp))
{
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
if (keep_buf)
*userbuf = buffer;
else
{
ReleaseBuffer(buffer);
*userbuf = InvalidBuffer;
}
tuple->t_data = NULL;
return false;
}
/*
* fill in *tuple fields
*/
tuple->t_data = (HeapTupleHeader) PageGetItem(page, lp);
tuple->t_len = ItemIdGetLength(lp);
tuple->t_tableOid = RelationGetRelid(relation);
/*
* check time qualification of tuple, then release lock
*/
valid = HeapTupleSatisfiesVisibility(tuple, snapshot, buffer);
if (valid)
PredicateLockTuple(relation, tuple, snapshot);
CheckForSerializableConflictOut(valid, relation, tuple, buffer, snapshot);
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
if (valid)
{
/*
* All checks passed, so return the tuple as valid. Caller is now
* responsible for releasing the buffer.
*/
*userbuf = buffer;
/* Count the successful fetch against appropriate rel, if any */
if (stats_relation != NULL)
pgstat_count_heap_fetch(stats_relation);
return true;
}
/* Tuple failed time qual, but maybe caller wants to see it anyway. */
if (keep_buf)
*userbuf = buffer;
else
{
ReleaseBuffer(buffer);
*userbuf = InvalidBuffer;
}
return false;
}
/*
* heap_hot_search_buffer - search HOT chain for tuple satisfying snapshot
*
* On entry, *tid is the TID of a tuple (either a simple tuple, or the root
* of a HOT chain), and buffer is the buffer holding this tuple. We search
* for the first chain member satisfying the given snapshot. If one is
* found, we update *tid to reference that tuple's offset number, and
* return TRUE. If no match, return FALSE without modifying *tid.
*
* heapTuple is a caller-supplied buffer. When a match is found, we return
* the tuple here, in addition to updating *tid. If no match is found, the
* contents of this buffer on return are undefined.
*
* If all_dead is not NULL, we check non-visible tuples to see if they are
* globally dead; *all_dead is set TRUE if all members of the HOT chain
* are vacuumable, FALSE if not.
*
* Unlike heap_fetch, the caller must already have pin and (at least) share
* lock on the buffer; it is still pinned/locked at exit. Also unlike
* heap_fetch, we do not report any pgstats count; caller may do so if wanted.
*/
bool
heap_hot_search_buffer(ItemPointer tid, Relation relation, Buffer buffer,
Snapshot snapshot, HeapTuple heapTuple,
bool *all_dead, bool first_call)
{
Page dp = (Page) BufferGetPage(buffer);
TransactionId prev_xmax = InvalidTransactionId;
OffsetNumber offnum;
bool at_chain_start;
bool valid;
bool skip;
/* If this is not the first call, previous call returned a (live!) tuple */
if (all_dead)
*all_dead = first_call;
Assert(TransactionIdIsValid(RecentGlobalXmin));
Assert(ItemPointerGetBlockNumber(tid) == BufferGetBlockNumber(buffer));
offnum = ItemPointerGetOffsetNumber(tid);
at_chain_start = first_call;
skip = !first_call;
/* Scan through possible multiple members of HOT-chain */
for (;;)
{
ItemId lp;
/* check for bogus TID */
if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(dp))
break;
lp = PageGetItemId(dp, offnum);
/* check for unused, dead, or redirected items */
if (!ItemIdIsNormal(lp))
{
/* We should only see a redirect at start of chain */
if (ItemIdIsRedirected(lp) && at_chain_start)
{
/* Follow the redirect */
offnum = ItemIdGetRedirect(lp);
at_chain_start = false;
continue;
}
/* else must be end of chain */
break;
}
heapTuple->t_data = (HeapTupleHeader) PageGetItem(dp, lp);
heapTuple->t_len = ItemIdGetLength(lp);
heapTuple->t_tableOid = relation->rd_id;
heapTuple->t_self = *tid;
/*
* Shouldn't see a HEAP_ONLY tuple at chain start.
*/
if (at_chain_start && HeapTupleIsHeapOnly(heapTuple))
break;
/*
* The xmin should match the previous xmax value, else chain is
* broken.
*/
if (TransactionIdIsValid(prev_xmax) &&
!TransactionIdEquals(prev_xmax,
HeapTupleHeaderGetXmin(heapTuple->t_data)))
break;
/*
* When first_call is true (and thus, skip is initially false) we'll
* return the first tuple we find. But on later passes, heapTuple
* will initially be pointing to the tuple we returned last time.
* Returning it again would be incorrect (and would loop forever),
* so we skip it and return the next match we find.
*/
if (!skip)
{
/* If it's visible per the snapshot, we must return it */
valid = HeapTupleSatisfiesVisibility(heapTuple, snapshot, buffer);
CheckForSerializableConflictOut(valid, relation, heapTuple,
buffer, snapshot);
if (valid)
{
ItemPointerSetOffsetNumber(tid, offnum);
PredicateLockTuple(relation, heapTuple, snapshot);
if (all_dead)
*all_dead = false;
return true;
}
}
skip = false;
/*
* If we can't see it, maybe no one else can either. At caller
* request, check whether all chain members are dead to all
* transactions.
*/
if (all_dead && *all_dead &&
HeapTupleSatisfiesVacuum(heapTuple->t_data, RecentGlobalXmin,
buffer) != HEAPTUPLE_DEAD)
*all_dead = false;
/*
* Check to see if HOT chain continues past this tuple; if so fetch
* the next offnum and loop around.
*/
if (HeapTupleIsHotUpdated(heapTuple))
{
Assert(ItemPointerGetBlockNumber(&heapTuple->t_data->t_ctid) ==
ItemPointerGetBlockNumber(tid));
offnum = ItemPointerGetOffsetNumber(&heapTuple->t_data->t_ctid);
at_chain_start = false;
prev_xmax = HeapTupleHeaderGetXmax(heapTuple->t_data);
}
else
break; /* end of chain */
}
return false;
}
/*
* heap_hot_search - search HOT chain for tuple satisfying snapshot
*
* This has the same API as heap_hot_search_buffer, except that the caller
* does not provide the buffer containing the page, rather we access it
* locally.
*/
bool
heap_hot_search(ItemPointer tid, Relation relation, Snapshot snapshot,
bool *all_dead)
{
bool result;
Buffer buffer;
HeapTupleData heapTuple;
buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid));
LockBuffer(buffer, BUFFER_LOCK_SHARE);
result = heap_hot_search_buffer(tid, relation, buffer, snapshot,
&heapTuple, all_dead, true);
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
ReleaseBuffer(buffer);
return result;
}
/*
* heap_get_latest_tid - get the latest tid of a specified tuple
*
* Actually, this gets the latest version that is visible according to
* the passed snapshot. You can pass SnapshotDirty to get the very latest,
* possibly uncommitted version.
*
* *tid is both an input and an output parameter: it is updated to
* show the latest version of the row. Note that it will not be changed
* if no version of the row passes the snapshot test.
*/
void
heap_get_latest_tid(Relation relation,
Snapshot snapshot,
ItemPointer tid)
{
BlockNumber blk;
ItemPointerData ctid;
TransactionId priorXmax;
/* this is to avoid Assert failures on bad input */
if (!ItemPointerIsValid(tid))
return;
/*
* Since this can be called with user-supplied TID, don't trust the input
* too much. (RelationGetNumberOfBlocks is an expensive check, so we
* don't check t_ctid links again this way. Note that it would not do to
* call it just once and save the result, either.)
*/
blk = ItemPointerGetBlockNumber(tid);
if (blk >= RelationGetNumberOfBlocks(relation))
elog(ERROR, "block number %u is out of range for relation \"%s\"",
blk, RelationGetRelationName(relation));
/*
* Loop to chase down t_ctid links. At top of loop, ctid is the tuple we
* need to examine, and *tid is the TID we will return if ctid turns out
* to be bogus.
*
* Note that we will loop until we reach the end of the t_ctid chain.
* Depending on the snapshot passed, there might be at most one visible
* version of the row, but we don't try to optimize for that.
*/
ctid = *tid;
priorXmax = InvalidTransactionId; /* cannot check first XMIN */
for (;;)
{
Buffer buffer;
Page page;
OffsetNumber offnum;
ItemId lp;
HeapTupleData tp;
bool valid;
/*
* Read, pin, and lock the page.
*/
buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(&ctid));
LockBuffer(buffer, BUFFER_LOCK_SHARE);
page = BufferGetPage(buffer);
/*
* Check for bogus item number. This is not treated as an error
* condition because it can happen while following a t_ctid link. We
* just assume that the prior tid is OK and return it unchanged.
*/
offnum = ItemPointerGetOffsetNumber(&ctid);
if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(page))
{
UnlockReleaseBuffer(buffer);
break;
}
lp = PageGetItemId(page, offnum);
if (!ItemIdIsNormal(lp))
{
UnlockReleaseBuffer(buffer);
break;
}
/* OK to access the tuple */
tp.t_self = ctid;
tp.t_data = (HeapTupleHeader) PageGetItem(page, lp);
tp.t_len = ItemIdGetLength(lp);
/*
* After following a t_ctid link, we might arrive at an unrelated
* tuple. Check for XMIN match.
*/
if (TransactionIdIsValid(priorXmax) &&
!TransactionIdEquals(priorXmax, HeapTupleHeaderGetXmin(tp.t_data)))
{
UnlockReleaseBuffer(buffer);
break;
}
/*
* Check time qualification of tuple; if visible, set it as the new
* result candidate.
*/
valid = HeapTupleSatisfiesVisibility(&tp, snapshot, buffer);
CheckForSerializableConflictOut(valid, relation, &tp, buffer, snapshot);
if (valid)
*tid = ctid;
/*
* If there's a valid t_ctid link, follow it, else we're done.
*/
if ((tp.t_data->t_infomask & (HEAP_XMAX_INVALID | HEAP_IS_LOCKED)) ||
ItemPointerEquals(&tp.t_self, &tp.t_data->t_ctid))
{
UnlockReleaseBuffer(buffer);
break;
}
ctid = tp.t_data->t_ctid;
priorXmax = HeapTupleHeaderGetXmax(tp.t_data);
UnlockReleaseBuffer(buffer);
} /* end of loop */
}
/*
* UpdateXmaxHintBits - update tuple hint bits after xmax transaction ends
*
* This is called after we have waited for the XMAX transaction to terminate.
* If the transaction aborted, we guarantee the XMAX_INVALID hint bit will
* be set on exit. If the transaction committed, we set the XMAX_COMMITTED
* hint bit if possible --- but beware that that may not yet be possible,
* if the transaction committed asynchronously. Hence callers should look
* only at XMAX_INVALID.
*/
static void
UpdateXmaxHintBits(HeapTupleHeader tuple, Buffer buffer, TransactionId xid)
{
Assert(TransactionIdEquals(HeapTupleHeaderGetXmax(tuple), xid));
if (!(tuple->t_infomask & (HEAP_XMAX_COMMITTED | HEAP_XMAX_INVALID)))
{
if (TransactionIdDidCommit(xid))
HeapTupleSetHintBits(tuple, buffer, HEAP_XMAX_COMMITTED,
xid);
else
HeapTupleSetHintBits(tuple, buffer, HEAP_XMAX_INVALID,
InvalidTransactionId);
}
}
/*
* GetBulkInsertState - prepare status object for a bulk insert
*/
BulkInsertState
GetBulkInsertState(void)
{
BulkInsertState bistate;
bistate = (BulkInsertState) palloc(sizeof(BulkInsertStateData));
bistate->strategy = GetAccessStrategy(BAS_BULKWRITE);
bistate->current_buf = InvalidBuffer;
return bistate;
}
/*
* FreeBulkInsertState - clean up after finishing a bulk insert
*/
void
FreeBulkInsertState(BulkInsertState bistate)
{
if (bistate->current_buf != InvalidBuffer)
ReleaseBuffer(bistate->current_buf);
FreeAccessStrategy(bistate->strategy);
pfree(bistate);
}
/*
* heap_insert - insert tuple into a heap
*
* The new tuple is stamped with current transaction ID and the specified
* command ID.
*
* If the HEAP_INSERT_SKIP_WAL option is specified, the new tuple is not
* logged in WAL, even for a non-temp relation. Safe usage of this behavior
* requires that we arrange that all new tuples go into new pages not
* containing any tuples from other transactions, and that the relation gets
* fsync'd before commit. (See also heap_sync() comments)
*
* The HEAP_INSERT_SKIP_FSM option is passed directly to
* RelationGetBufferForTuple, which see for more info.
*
* Note that these options will be applied when inserting into the heap's
* TOAST table, too, if the tuple requires any out-of-line data.
*
* The BulkInsertState object (if any; bistate can be NULL for default
* behavior) is also just passed through to RelationGetBufferForTuple.
*
* The return value is the OID assigned to the tuple (either here or by the
* caller), or InvalidOid if no OID. The header fields of *tup are updated
* to match the stored tuple; in particular tup->t_self receives the actual
* TID where the tuple was stored. But note that any toasting of fields
* within the tuple data is NOT reflected into *tup.
*/
Oid
heap_insert(Relation relation, HeapTuple tup, CommandId cid,
int options, BulkInsertState bistate)
{
TransactionId xid = GetCurrentTransactionId();
HeapTuple heaptup;
Buffer buffer;
Buffer vmbuffer = InvalidBuffer;
bool all_visible_cleared = false;
/*
* Fill in tuple header fields, assign an OID, and toast the tuple if
* necessary.
*
* Note: below this point, heaptup is the data we actually intend to store
* into the relation; tup is the caller's original untoasted data.
*/
heaptup = heap_prepare_insert(relation, tup, xid, cid, options);
/*
* We're about to do the actual insert -- but check for conflict first,
* to avoid possibly having to roll back work we've just done.
*
* For a heap insert, we only need to check for table-level SSI locks.
* Our new tuple can't possibly conflict with existing tuple locks, and
* heap page locks are only consolidated versions of tuple locks; they do
* not lock "gaps" as index page locks do. So we don't need to identify
* a buffer before making the call.
*/
CheckForSerializableConflictIn(relation, NULL, InvalidBuffer);
/*
* Find buffer to insert this tuple into. If the page is all visible,
* this will also pin the requisite visibility map page.
*/
buffer = RelationGetBufferForTuple(relation, heaptup->t_len,
InvalidBuffer, options, bistate,
&vmbuffer, NULL);
/* NO EREPORT(ERROR) from here till changes are logged */
START_CRIT_SECTION();
RelationPutHeapTuple(relation, buffer, heaptup);
if (PageIsAllVisible(BufferGetPage(buffer)))
{
all_visible_cleared = true;
PageClearAllVisible(BufferGetPage(buffer));
visibilitymap_clear(relation,
ItemPointerGetBlockNumber(&(heaptup->t_self)),
vmbuffer);
}
/*
* XXX Should we set PageSetPrunable on this page ?
*
* The inserting transaction may eventually abort thus making this tuple
* DEAD and hence available for pruning. Though we don't want to optimize
* for aborts, if no other tuple in this page is UPDATEd/DELETEd, the
* aborted tuple will never be pruned until next vacuum is triggered.
*
* If you do add PageSetPrunable here, add it in heap_xlog_insert too.
*/
MarkBufferDirty(buffer);
/* XLOG stuff */
if (!(options & HEAP_INSERT_SKIP_WAL) && RelationNeedsWAL(relation))
{
xl_heap_insert xlrec;
xl_heap_header xlhdr;
XLogRecPtr recptr;
XLogRecData rdata[3];
Page page = BufferGetPage(buffer);
uint8 info = XLOG_HEAP_INSERT;
xlrec.all_visible_cleared = all_visible_cleared;
xlrec.target.node = relation->rd_node;
xlrec.target.tid = heaptup->t_self;
rdata[0].data = (char *) &xlrec;
rdata[0].len = SizeOfHeapInsert;
rdata[0].buffer = InvalidBuffer;
rdata[0].next = &(rdata[1]);
xlhdr.t_infomask2 = heaptup->t_data->t_infomask2;
xlhdr.t_infomask = heaptup->t_data->t_infomask;
xlhdr.t_hoff = heaptup->t_data->t_hoff;
/*
* note we mark rdata[1] as belonging to buffer; if XLogInsert decides
* to write the whole page to the xlog, we don't need to store
* xl_heap_header in the xlog.
*/
rdata[1].data = (char *) &xlhdr;
rdata[1].len = SizeOfHeapHeader;
rdata[1].buffer = buffer;
rdata[1].buffer_std = true;
rdata[1].next = &(rdata[2]);
/* PG73FORMAT: write bitmap [+ padding] [+ oid] + data */
rdata[2].data = (char *) heaptup->t_data + offsetof(HeapTupleHeaderData, t_bits);
rdata[2].len = heaptup->t_len - offsetof(HeapTupleHeaderData, t_bits);
rdata[2].buffer = buffer;
rdata[2].buffer_std = true;
rdata[2].next = NULL;
/*
* If this is the single and first tuple on page, we can reinit the
* page instead of restoring the whole thing. Set flag, and hide
* buffer references from XLogInsert.
*/
if (ItemPointerGetOffsetNumber(&(heaptup->t_self)) == FirstOffsetNumber &&
PageGetMaxOffsetNumber(page) == FirstOffsetNumber)
{
info |= XLOG_HEAP_INIT_PAGE;
rdata[1].buffer = rdata[2].buffer = InvalidBuffer;
}
recptr = XLogInsert(RM_HEAP_ID, info, rdata);
PageSetLSN(page, recptr);
PageSetTLI(page, ThisTimeLineID);
}
END_CRIT_SECTION();
UnlockReleaseBuffer(buffer);
if (vmbuffer != InvalidBuffer)
ReleaseBuffer(vmbuffer);
/*
* If tuple is cachable, mark it for invalidation from the caches in case
* we abort. Note it is OK to do this after releasing the buffer, because
* the heaptup data structure is all in local memory, not in the shared
* buffer.
*/
CacheInvalidateHeapTuple(relation, heaptup, NULL);
pgstat_count_heap_insert(relation, 1);
/*
* If heaptup is a private copy, release it. Don't forget to copy t_self
* back to the caller's image, too.
*/
if (heaptup != tup)
{
tup->t_self = heaptup->t_self;
heap_freetuple(heaptup);
}
return HeapTupleGetOid(tup);
}
/*
* Subroutine for heap_insert(). Prepares a tuple for insertion. This sets the
* tuple header fields, assigns an OID, and toasts the tuple if necessary.
* Returns a toasted version of the tuple if it was toasted, or the original
* tuple if not. Note that in any case, the header fields are also set in
* the original tuple.
*/
static HeapTuple
heap_prepare_insert(Relation relation, HeapTuple tup, TransactionId xid,
CommandId cid, int options)
{
if (relation->rd_rel->relhasoids)
{
#ifdef NOT_USED
/* this is redundant with an Assert in HeapTupleSetOid */
Assert(tup->t_data->t_infomask & HEAP_HASOID);
#endif
/*
* If the object id of this tuple has already been assigned, trust the
* caller. There are a couple of ways this can happen. At initial db
* creation, the backend program sets oids for tuples. When we define
* an index, we set the oid. Finally, in the future, we may allow
* users to set their own object ids in order to support a persistent
* object store (objects need to contain pointers to one another).
*/
if (!OidIsValid(HeapTupleGetOid(tup)))
HeapTupleSetOid(tup, GetNewOid(relation));
}
else
{
/* check there is not space for an OID */
Assert(!(tup->t_data->t_infomask & HEAP_HASOID));
}
tup->t_data->t_infomask &= ~(HEAP_XACT_MASK);
tup->t_data->t_infomask2 &= ~(HEAP2_XACT_MASK);
tup->t_data->t_infomask |= HEAP_XMAX_INVALID;
HeapTupleHeaderSetXmin(tup->t_data, xid);
HeapTupleHeaderSetCmin(tup->t_data, cid);
HeapTupleHeaderSetXmax(tup->t_data, 0); /* for cleanliness */
tup->t_tableOid = RelationGetRelid(relation);
/*
* If the new tuple is too big for storage or contains already toasted
* out-of-line attributes from some other relation, invoke the toaster.
*/
if (relation->rd_rel->relkind != RELKIND_RELATION)
{
/* toast table entries should never be recursively toasted */
Assert(!HeapTupleHasExternal(tup));
return tup;
}
else if (HeapTupleHasExternal(tup) || tup->t_len > TOAST_TUPLE_THRESHOLD)
return toast_insert_or_update(relation, tup, NULL, options);
else
return tup;
}
/*
* heap_multi_insert - insert multiple tuple into a heap
*
* This is like heap_insert(), but inserts multiple tuples in one operation.
* That's faster than calling heap_insert() in a loop, because when multiple
* tuples can be inserted on a single page, we can write just a single WAL
* record covering all of them, and only need to lock/unlock the page once.
*
* Note: this leaks memory into the current memory context. You can create a
* temporary context before calling this, if that's a problem.
*/
void
heap_multi_insert(Relation relation, HeapTuple *tuples, int ntuples,
CommandId cid, int options, BulkInsertState bistate)
{
TransactionId xid = GetCurrentTransactionId();
HeapTuple *heaptuples;
int i;
int ndone;
char *scratch = NULL;
Page page;
bool needwal;
Size saveFreeSpace;
needwal = !(options & HEAP_INSERT_SKIP_WAL) && RelationNeedsWAL(relation);
saveFreeSpace = RelationGetTargetPageFreeSpace(relation,
HEAP_DEFAULT_FILLFACTOR);
/* Toast and set header data in all the tuples */
heaptuples = palloc(ntuples * sizeof(HeapTuple));
for (i = 0; i < ntuples; i++)
heaptuples[i] = heap_prepare_insert(relation, tuples[i],
xid, cid, options);
/*
* Allocate some memory to use for constructing the WAL record. Using
* palloc() within a critical section is not safe, so we allocate this
* beforehand.
*/
if (needwal)
scratch = palloc(BLCKSZ);
/*
* We're about to do the actual inserts -- but check for conflict first,
* to avoid possibly having to roll back work we've just done.
*
* For a heap insert, we only need to check for table-level SSI locks.
* Our new tuple can't possibly conflict with existing tuple locks, and
* heap page locks are only consolidated versions of tuple locks; they do
* not lock "gaps" as index page locks do. So we don't need to identify
* a buffer before making the call.
*/
CheckForSerializableConflictIn(relation, NULL, InvalidBuffer);
ndone = 0;
while (ndone < ntuples)
{
Buffer buffer;
Buffer vmbuffer = InvalidBuffer;
bool all_visible_cleared = false;
int nthispage;
/*
* Find buffer where at least the next tuple will fit. If the page
* is all-visible, this will also pin the requisite visibility map
* page.
*/
buffer = RelationGetBufferForTuple(relation, heaptuples[ndone]->t_len,
InvalidBuffer, options, bistate,
&vmbuffer, NULL);
page = BufferGetPage(buffer);
if (PageIsAllVisible(page))
{
all_visible_cleared = true;
PageClearAllVisible(page);
visibilitymap_clear(relation,
BufferGetBlockNumber(buffer),
vmbuffer);
}
/* NO EREPORT(ERROR) from here till changes are logged */
START_CRIT_SECTION();
/* Put as many tuples as fit on this page */
for (nthispage = 0; ndone + nthispage < ntuples; nthispage++)
{
HeapTuple heaptup = heaptuples[ndone + nthispage];
if (PageGetHeapFreeSpace(page) - saveFreeSpace < MAXALIGN(heaptup->t_len))
break;
RelationPutHeapTuple(relation, buffer, heaptup);
}
/*
* XXX Should we set PageSetPrunable on this page ? See heap_insert()
*/
MarkBufferDirty(buffer);
/* XLOG stuff */
if (needwal)
{
XLogRecPtr recptr;
xl_heap_multi_insert *xlrec;
XLogRecData rdata[2];
uint8 info = XLOG_HEAP2_MULTI_INSERT;
char *tupledata;
int totaldatalen;
char *scratchptr = scratch;
bool init;
/*
* If the page was previously empty, we can reinit the page
* instead of restoring the whole thing.
*/
init = (ItemPointerGetOffsetNumber(&(heaptuples[ndone]->t_self)) == FirstOffsetNumber &&
PageGetMaxOffsetNumber(page) == FirstOffsetNumber + nthispage - 1);
/* allocate xl_heap_multi_insert struct from the scratch area */
xlrec = (xl_heap_multi_insert *) scratchptr;
scratchptr += SizeOfHeapMultiInsert;
/*
* Allocate offsets array. Unless we're reinitializing the page,
* in that case the tuples are stored in order starting at
* FirstOffsetNumber and we don't need to store the offsets
* explicitly.
*/
if (!init)
scratchptr += nthispage * sizeof(OffsetNumber);
/* the rest of the scratch space is used for tuple data */
tupledata = scratchptr;
xlrec->all_visible_cleared = all_visible_cleared;
xlrec->node = relation->rd_node;
xlrec->blkno = BufferGetBlockNumber(buffer);
xlrec->ntuples = nthispage;
/*
* Write out an xl_multi_insert_tuple and the tuple data itself
* for each tuple.
*/
for (i = 0; i < nthispage; i++)
{
HeapTuple heaptup = heaptuples[ndone + i];
xl_multi_insert_tuple *tuphdr;
int datalen;
if (!init)
xlrec->offsets[i] = ItemPointerGetOffsetNumber(&heaptup->t_self);
/* xl_multi_insert_tuple needs two-byte alignment. */
tuphdr = (xl_multi_insert_tuple *) SHORTALIGN(scratchptr);
scratchptr = ((char *) tuphdr) + SizeOfMultiInsertTuple;
tuphdr->t_infomask2 = heaptup->t_data->t_infomask2;
tuphdr->t_infomask = heaptup->t_data->t_infomask;
tuphdr->t_hoff = heaptup->t_data->t_hoff;
/* write bitmap [+ padding] [+ oid] + data */
datalen = heaptup->t_len - offsetof(HeapTupleHeaderData, t_bits);
memcpy(scratchptr,
(char *) heaptup->t_data + offsetof(HeapTupleHeaderData, t_bits),
datalen);
tuphdr->datalen = datalen;
scratchptr += datalen;
}
totaldatalen = scratchptr - tupledata;
Assert((scratchptr - scratch) < BLCKSZ);
rdata[0].data = (char *) xlrec;
rdata[0].len = tupledata - scratch;
rdata[0].buffer = InvalidBuffer;
rdata[0].next = &rdata[1];
rdata[1].data = tupledata;
rdata[1].len = totaldatalen;
rdata[1].buffer = buffer;
rdata[1].buffer_std = true;
rdata[1].next = NULL;
/*
* If we're going to reinitialize the whole page using the WAL
* record, hide buffer reference from XLogInsert.
*/
if (init)
{
rdata[1].buffer = InvalidBuffer;
info |= XLOG_HEAP_INIT_PAGE;
}
recptr = XLogInsert(RM_HEAP2_ID, info, rdata);
PageSetLSN(page, recptr);
PageSetTLI(page, ThisTimeLineID);
}
END_CRIT_SECTION();
UnlockReleaseBuffer(buffer);
if (vmbuffer != InvalidBuffer)
ReleaseBuffer(vmbuffer);
ndone += nthispage;
}
/*
* If tuples are cachable, mark them for invalidation from the caches in
* case we abort. Note it is OK to do this after releasing the buffer,
* because the heaptuples data structure is all in local memory, not in
* the shared buffer.
*/
if (IsSystemRelation(relation))
{
for (i = 0; i < ntuples; i++)
CacheInvalidateHeapTuple(relation, heaptuples[i], NULL);
}
/*
* Copy t_self fields back to the caller's original tuples. This does
* nothing for untoasted tuples (tuples[i] == heaptuples[i)], but it's
* probably faster to always copy than check.
*/
for (i = 0; i < ntuples; i++)
tuples[i]->t_self = heaptuples[i]->t_self;
pgstat_count_heap_insert(relation, ntuples);
}
/*
* simple_heap_insert - insert a tuple
*
* Currently, this routine differs from heap_insert only in supplying
* a default command ID and not allowing access to the speedup options.
*
* This should be used rather than using heap_insert directly in most places
* where we are modifying system catalogs.
*/
Oid
simple_heap_insert(Relation relation, HeapTuple tup)
{
return heap_insert(relation, tup, GetCurrentCommandId(true), 0, NULL);
}
/*
* heap_delete - delete a tuple
*
* NB: do not call this directly unless you are prepared to deal with
* concurrent-update conditions. Use simple_heap_delete instead.
*
* relation - table to be modified (caller must hold suitable lock)
* tid - TID of tuple to be deleted
* ctid - output parameter, used only for failure case (see below)
* update_xmax - output parameter, used only for failure case (see below)
* cid - delete command ID (used for visibility test, and stored into
* cmax if successful)
* crosscheck - if not InvalidSnapshot, also check tuple against this
* wait - true if should wait for any conflicting update to commit/abort
*
* Normal, successful return value is HeapTupleMayBeUpdated, which
* actually means we did delete it. Failure return codes are
* HeapTupleSelfUpdated, HeapTupleUpdated, or HeapTupleBeingUpdated
* (the last only possible if wait == false).
*
* In the failure cases, the routine returns the tuple's t_ctid and t_xmax.
* If t_ctid is the same as tid, the tuple was deleted; if different, the
* tuple was updated, and t_ctid is the location of the replacement tuple.
* (t_xmax is needed to verify that the replacement tuple matches.)
*/
HTSU_Result
heap_delete(Relation relation, ItemPointer tid,
ItemPointer ctid, TransactionId *update_xmax,
CommandId cid, Snapshot crosscheck, bool wait)
{
HTSU_Result result;
TransactionId xid = GetCurrentTransactionId();
ItemId lp;
HeapTupleData tp;
Page page;
BlockNumber block;
Buffer buffer;
Buffer vmbuffer = InvalidBuffer;
bool have_tuple_lock = false;
bool iscombo;
bool all_visible_cleared = false;
Assert(ItemPointerIsValid(tid));
block = ItemPointerGetBlockNumber(tid);
buffer = ReadBuffer(relation, block);
page = BufferGetPage(buffer);
/*
* Before locking the buffer, pin the visibility map page if it appears
* to be necessary. Since we haven't got the lock yet, someone else might
* be in the middle of changing this, so we'll need to recheck after
* we have the lock.
*/
if (PageIsAllVisible(page))
visibilitymap_pin(relation, block, &vmbuffer);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
/*
* If we didn't pin the visibility map page and the page has become all
* visible while we were busy locking the buffer, we'll have to unlock and
* re-lock, to avoid holding the buffer lock across an I/O. That's a bit
* unfortunate, but hopefully shouldn't happen often.
*/
if (vmbuffer == InvalidBuffer && PageIsAllVisible(page))
{
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
visibilitymap_pin(relation, block, &vmbuffer);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
}
lp = PageGetItemId(page, ItemPointerGetOffsetNumber(tid));
Assert(ItemIdIsNormal(lp));
tp.t_data = (HeapTupleHeader) PageGetItem(page, lp);
tp.t_len = ItemIdGetLength(lp);
tp.t_self = *tid;
l1:
result = HeapTupleSatisfiesUpdate(tp.t_data, cid, buffer);
if (result == HeapTupleInvisible)
{
UnlockReleaseBuffer(buffer);
elog(ERROR, "attempted to delete invisible tuple");
}
else if (result == HeapTupleBeingUpdated && wait)
{
TransactionId xwait;
uint16 infomask;
/* must copy state data before unlocking buffer */
xwait = HeapTupleHeaderGetXmax(tp.t_data);
infomask = tp.t_data->t_infomask;
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
/*
* Acquire tuple lock to establish our priority for the tuple (see
* heap_lock_tuple). LockTuple will release us when we are
* next-in-line for the tuple.
*
* If we are forced to "start over" below, we keep the tuple lock;
* this arranges that we stay at the head of the line while rechecking
* tuple state.
*/
if (!have_tuple_lock)
{
LockTuple(relation, &(tp.t_self), ExclusiveLock);
have_tuple_lock = true;
}
/*
* Sleep until concurrent transaction ends. Note that we don't care
* if the locker has an exclusive or shared lock, because we need
* exclusive.
*/
if (infomask & HEAP_XMAX_IS_MULTI)
{
/* wait for multixact */
MultiXactIdWait((MultiXactId) xwait);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
/*
* If xwait had just locked the tuple then some other xact could
* update this tuple before we get to this point. Check for xmax
* change, and start over if so.
*/
if (!(tp.t_data->t_infomask & HEAP_XMAX_IS_MULTI) ||
!TransactionIdEquals(HeapTupleHeaderGetXmax(tp.t_data),
xwait))
goto l1;
/*
* You might think the multixact is necessarily done here, but not
* so: it could have surviving members, namely our own xact or
* other subxacts of this backend. It is legal for us to delete
* the tuple in either case, however (the latter case is
* essentially a situation of upgrading our former shared lock to
* exclusive). We don't bother changing the on-disk hint bits
* since we are about to overwrite the xmax altogether.
*/
}
else
{
/* wait for regular transaction to end */
XactLockTableWait(xwait);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
/*
* xwait is done, but if xwait had just locked the tuple then some
* other xact could update this tuple before we get to this point.
* Check for xmax change, and start over if so.
*/
if ((tp.t_data->t_infomask & HEAP_XMAX_IS_MULTI) ||
!TransactionIdEquals(HeapTupleHeaderGetXmax(tp.t_data),
xwait))
goto l1;
/* Otherwise check if it committed or aborted */
UpdateXmaxHintBits(tp.t_data, buffer, xwait);
}
/*
* We may overwrite if previous xmax aborted, or if it committed but
* only locked the tuple without updating it.
*/
if (tp.t_data->t_infomask & (HEAP_XMAX_INVALID |
HEAP_IS_LOCKED))
result = HeapTupleMayBeUpdated;
else
result = HeapTupleUpdated;
}
if (crosscheck != InvalidSnapshot && result == HeapTupleMayBeUpdated)
{
/* Perform additional check for transaction-snapshot mode RI updates */
if (!HeapTupleSatisfiesVisibility(&tp, crosscheck, buffer))
result = HeapTupleUpdated;
}
if (result != HeapTupleMayBeUpdated)
{
Assert(result == HeapTupleSelfUpdated ||
result == HeapTupleUpdated ||
result == HeapTupleBeingUpdated);
Assert(!(tp.t_data->t_infomask & HEAP_XMAX_INVALID));
*ctid = tp.t_data->t_ctid;
*update_xmax = HeapTupleHeaderGetXmax(tp.t_data);
UnlockReleaseBuffer(buffer);
if (have_tuple_lock)
UnlockTuple(relation, &(tp.t_self), ExclusiveLock);
if (vmbuffer != InvalidBuffer)
ReleaseBuffer(vmbuffer);
return result;
}
/*
* We're about to do the actual delete -- check for conflict first, to
* avoid possibly having to roll back work we've just done.
*/
CheckForSerializableConflictIn(relation, &tp, buffer);
/* replace cid with a combo cid if necessary */
HeapTupleHeaderAdjustCmax(tp.t_data, &cid, &iscombo);
START_CRIT_SECTION();
/*
* If this transaction commits, the tuple will become DEAD sooner or
* later. Set flag that this page is a candidate for pruning once our xid
* falls below the OldestXmin horizon. If the transaction finally aborts,
* the subsequent page pruning will be a no-op and the hint will be
* cleared.
*/
PageSetPrunable(page, xid);
if (PageIsAllVisible(page))
{
all_visible_cleared = true;
PageClearAllVisible(page);
visibilitymap_clear(relation, BufferGetBlockNumber(buffer),
vmbuffer);
}
/* store transaction information of xact deleting the tuple */
tp.t_data->t_infomask &= ~(HEAP_XMAX_COMMITTED |
HEAP_XMAX_INVALID |
HEAP_XMAX_IS_MULTI |
HEAP_IS_LOCKED |
HEAP_MOVED);
HeapTupleHeaderClearHotUpdated(tp.t_data);
HeapTupleHeaderSetXmax(tp.t_data, xid);
HeapTupleHeaderSetCmax(tp.t_data, cid, iscombo);
/* Make sure there is no forward chain link in t_ctid */
tp.t_data->t_ctid = tp.t_self;
MarkBufferDirty(buffer);
/* XLOG stuff */
if (RelationNeedsWAL(relation))
{
xl_heap_delete xlrec;
XLogRecPtr recptr;
XLogRecData rdata[2];
xlrec.all_visible_cleared = all_visible_cleared;
xlrec.target.node = relation->rd_node;
xlrec.target.tid = tp.t_self;
rdata[0].data = (char *) &xlrec;
rdata[0].len = SizeOfHeapDelete;
rdata[0].buffer = InvalidBuffer;
rdata[0].next = &(rdata[1]);
rdata[1].data = NULL;
rdata[1].len = 0;
rdata[1].buffer = buffer;
rdata[1].buffer_std = true;
rdata[1].next = NULL;
recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_DELETE, rdata);
PageSetLSN(page, recptr);
PageSetTLI(page, ThisTimeLineID);
}
END_CRIT_SECTION();
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
if (vmbuffer != InvalidBuffer)
ReleaseBuffer(vmbuffer);
/*
* If the tuple has toasted out-of-line attributes, we need to delete
* those items too. We have to do this before releasing the buffer
* because we need to look at the contents of the tuple, but it's OK to
* release the content lock on the buffer first.
*/
if (relation->rd_rel->relkind != RELKIND_RELATION)
{
/* toast table entries should never be recursively toasted */
Assert(!HeapTupleHasExternal(&tp));
}
else if (HeapTupleHasExternal(&tp))
toast_delete(relation, &tp);
/*
* Mark tuple for invalidation from system caches at next command
* boundary. We have to do this before releasing the buffer because we
* need to look at the contents of the tuple.
*/
CacheInvalidateHeapTuple(relation, &tp, NULL);
/* Now we can release the buffer */
ReleaseBuffer(buffer);
/*
* Release the lmgr tuple lock, if we had it.
*/
if (have_tuple_lock)
UnlockTuple(relation, &(tp.t_self), ExclusiveLock);
pgstat_count_heap_delete(relation);
return HeapTupleMayBeUpdated;
}
/*
* simple_heap_delete - delete a tuple
*
* This routine may be used to delete a tuple when concurrent updates of
* the target tuple are not expected (for example, because we have a lock
* on the relation associated with the tuple). Any failure is reported
* via ereport().
*/
void
simple_heap_delete(Relation relation, ItemPointer tid)
{
HTSU_Result result;
ItemPointerData update_ctid;
TransactionId update_xmax;
result = heap_delete(relation, tid,
&update_ctid, &update_xmax,
GetCurrentCommandId(true), InvalidSnapshot,
true /* wait for commit */ );
switch (result)
{
case HeapTupleSelfUpdated:
/* Tuple was already updated in current command? */
elog(ERROR, "tuple already updated by self");
break;
case HeapTupleMayBeUpdated:
/* done successfully */
break;
case HeapTupleUpdated:
elog(ERROR, "tuple concurrently updated");
break;
default:
elog(ERROR, "unrecognized heap_delete status: %u", result);
break;
}
}
/*
* heap_update - replace a tuple
*
* NB: do not call this directly unless you are prepared to deal with
* concurrent-update conditions. Use simple_heap_update instead.
*
* relation - table to be modified (caller must hold suitable lock)
* otid - TID of old tuple to be replaced
* newtup - newly constructed tuple data to store
* ctid - output parameter, used only for failure case (see below)
* update_xmax - output parameter, used only for failure case (see below)
* cid - update command ID (used for visibility test, and stored into
* cmax/cmin if successful)
* crosscheck - if not InvalidSnapshot, also check old tuple against this
* wait - true if should wait for any conflicting update to commit/abort
*
* Normal, successful return value is HeapTupleMayBeUpdated, which
* actually means we *did* update it. Failure return codes are
* HeapTupleSelfUpdated, HeapTupleUpdated, or HeapTupleBeingUpdated
* (the last only possible if wait == false).
*
* On success, the header fields of *newtup are updated to match the new
* stored tuple; in particular, newtup->t_self is set to the TID where the
* new tuple was inserted, and its HEAP_ONLY_TUPLE flag is set iff a HOT
* update was done. However, any TOAST changes in the new tuple's
* data are not reflected into *newtup.
*
* In the failure cases, the routine returns the tuple's t_ctid and t_xmax.
* If t_ctid is the same as otid, the tuple was deleted; if different, the
* tuple was updated, and t_ctid is the location of the replacement tuple.
* (t_xmax is needed to verify that the replacement tuple matches.)
*/
HTSU_Result
heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
ItemPointer ctid, TransactionId *update_xmax,
CommandId cid, Snapshot crosscheck, bool wait)
{
HTSU_Result result;
TransactionId xid = GetCurrentTransactionId();
Bitmapset *hot_attrs;
ItemId lp;
HeapTupleData oldtup;
HeapTuple heaptup;
Page page;
BlockNumber block;
Buffer buffer,
newbuf,
vmbuffer = InvalidBuffer,
vmbuffer_new = InvalidBuffer;
bool need_toast,
already_marked;
Size newtupsize,
pagefree;
bool have_tuple_lock = false;
bool iscombo;
bool use_hot_update = false;
bool all_visible_cleared = false;
bool all_visible_cleared_new = false;
Assert(ItemPointerIsValid(otid));
/*
* Fetch the list of attributes to be checked for HOT update. This is
* wasted effort if we fail to update or have to put the new tuple on a
* different page. But we must compute the list before obtaining buffer
* lock --- in the worst case, if we are doing an update on one of the
* relevant system catalogs, we could deadlock if we try to fetch the list
* later. In any case, the relcache caches the data so this is usually
* pretty cheap.
*
* Note that we get a copy here, so we need not worry about relcache flush
* happening midway through.
*/
hot_attrs = RelationGetIndexAttrBitmap(relation);
block = ItemPointerGetBlockNumber(otid);
buffer = ReadBuffer(relation, block);
page = BufferGetPage(buffer);
/*
* Before locking the buffer, pin the visibility map page if it appears
* to be necessary. Since we haven't got the lock yet, someone else might
* be in the middle of changing this, so we'll need to recheck after
* we have the lock.
*/
if (PageIsAllVisible(page))
visibilitymap_pin(relation, block, &vmbuffer);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
lp = PageGetItemId(page, ItemPointerGetOffsetNumber(otid));
Assert(ItemIdIsNormal(lp));
oldtup.t_data = (HeapTupleHeader) PageGetItem(page, lp);
oldtup.t_len = ItemIdGetLength(lp);
oldtup.t_self = *otid;
/*
* Note: beyond this point, use oldtup not otid to refer to old tuple.
* otid may very well point at newtup->t_self, which we will overwrite
* with the new tuple's location, so there's great risk of confusion if we
* use otid anymore.
*/
l2:
result = HeapTupleSatisfiesUpdate(oldtup.t_data, cid, buffer);
if (result == HeapTupleInvisible)
{
UnlockReleaseBuffer(buffer);
elog(ERROR, "attempted to update invisible tuple");
}
else if (result == HeapTupleBeingUpdated && wait)
{
TransactionId xwait;
uint16 infomask;
/* must copy state data before unlocking buffer */
xwait = HeapTupleHeaderGetXmax(oldtup.t_data);
infomask = oldtup.t_data->t_infomask;
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
/*
* Acquire tuple lock to establish our priority for the tuple (see
* heap_lock_tuple). LockTuple will release us when we are
* next-in-line for the tuple.
*
* If we are forced to "start over" below, we keep the tuple lock;
* this arranges that we stay at the head of the line while rechecking
* tuple state.
*/
if (!have_tuple_lock)
{
LockTuple(relation, &(oldtup.t_self), ExclusiveLock);
have_tuple_lock = true;
}
/*
* Sleep until concurrent transaction ends. Note that we don't care
* if the locker has an exclusive or shared lock, because we need
* exclusive.
*/
if (infomask & HEAP_XMAX_IS_MULTI)
{
/* wait for multixact */
MultiXactIdWait((MultiXactId) xwait);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
/*
* If xwait had just locked the tuple then some other xact could
* update this tuple before we get to this point. Check for xmax
* change, and start over if so.
*/
if (!(oldtup.t_data->t_infomask & HEAP_XMAX_IS_MULTI) ||
!TransactionIdEquals(HeapTupleHeaderGetXmax(oldtup.t_data),
xwait))
goto l2;
/*
* You might think the multixact is necessarily done here, but not
* so: it could have surviving members, namely our own xact or
* other subxacts of this backend. It is legal for us to update
* the tuple in either case, however (the latter case is
* essentially a situation of upgrading our former shared lock to
* exclusive). We don't bother changing the on-disk hint bits
* since we are about to overwrite the xmax altogether.
*/
}
else
{
/* wait for regular transaction to end */
XactLockTableWait(xwait);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
/*
* xwait is done, but if xwait had just locked the tuple then some
* other xact could update this tuple before we get to this point.
* Check for xmax change, and start over if so.
*/
if ((oldtup.t_data->t_infomask & HEAP_XMAX_IS_MULTI) ||
!TransactionIdEquals(HeapTupleHeaderGetXmax(oldtup.t_data),
xwait))
goto l2;
/* Otherwise check if it committed or aborted */
UpdateXmaxHintBits(oldtup.t_data, buffer, xwait);
}
/*
* We may overwrite if previous xmax aborted, or if it committed but
* only locked the tuple without updating it.
*/
if (oldtup.t_data->t_infomask & (HEAP_XMAX_INVALID |
HEAP_IS_LOCKED))
result = HeapTupleMayBeUpdated;
else
result = HeapTupleUpdated;
}
if (crosscheck != InvalidSnapshot && result == HeapTupleMayBeUpdated)
{
/* Perform additional check for transaction-snapshot mode RI updates */
if (!HeapTupleSatisfiesVisibility(&oldtup, crosscheck, buffer))
result = HeapTupleUpdated;
}
if (result != HeapTupleMayBeUpdated)
{
Assert(result == HeapTupleSelfUpdated ||
result == HeapTupleUpdated ||
result == HeapTupleBeingUpdated);
Assert(!(oldtup.t_data->t_infomask & HEAP_XMAX_INVALID));
*ctid = oldtup.t_data->t_ctid;
*update_xmax = HeapTupleHeaderGetXmax(oldtup.t_data);
UnlockReleaseBuffer(buffer);
if (have_tuple_lock)
UnlockTuple(relation, &(oldtup.t_self), ExclusiveLock);
if (vmbuffer != InvalidBuffer)
ReleaseBuffer(vmbuffer);
bms_free(hot_attrs);
return result;
}
/*
* If we didn't pin the visibility map page and the page has become all
* visible while we were busy locking the buffer, or during some subsequent
* window during which we had it unlocked, we'll have to unlock and
* re-lock, to avoid holding the buffer lock across an I/O. That's a bit
* unfortunate, esepecially since we'll now have to recheck whether the
* tuple has been locked or updated under us, but hopefully it won't
* happen very often.
*/
if (vmbuffer == InvalidBuffer && PageIsAllVisible(page))
{
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
visibilitymap_pin(relation, block, &vmbuffer);
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
goto l2;
}
/*
* We're about to do the actual update -- check for conflict first, to
* avoid possibly having to roll back work we've just done.
*/
CheckForSerializableConflictIn(relation, &oldtup, buffer);
/* Fill in OID and transaction status data for newtup */
if (relation->rd_rel->relhasoids)
{
#ifdef NOT_USED
/* this is redundant with an Assert in HeapTupleSetOid */
Assert(newtup->t_data->t_infomask & HEAP_HASOID);
#endif
HeapTupleSetOid(newtup, HeapTupleGetOid(&oldtup));
}
else
{
/* check there is not space for an OID */
Assert(!(newtup->t_data->t_infomask & HEAP_HASOID));
}
newtup->t_data->t_infomask &= ~(HEAP_XACT_MASK);
newtup->t_data->t_infomask2 &= ~(HEAP2_XACT_MASK);
newtup->t_data->t_infomask |= (HEAP_XMAX_INVALID | HEAP_UPDATED);
HeapTupleHeaderSetXmin(newtup->t_data, xid);
HeapTupleHeaderSetCmin(newtup->t_data, cid);
HeapTupleHeaderSetXmax(newtup->t_data, 0); /* for cleanliness */
newtup->t_tableOid = RelationGetRelid(relation);
/*
* Replace cid with a combo cid if necessary. Note that we already put
* the plain cid into the new tuple.
*/
HeapTupleHeaderAdjustCmax(oldtup.t_data, &cid, &iscombo);
/*
* If the toaster needs to be activated, OR if the new tuple will not fit
* on the same page as the old, then we need to release the content lock
* (but not the pin!) on the old tuple's buffer while we are off doing
* TOAST and/or table-file-extension work. We must mark the old tuple to
* show that it's already being updated, else other processes may try to
* update it themselves.
*
* We need to invoke the toaster if there are already any out-of-line
* toasted values present, or if the new tuple is over-threshold.
*/
if (relation->rd_rel->relkind != RELKIND_RELATION)
{
/* toast table entries should never be recursively toasted */
Assert(!HeapTupleHasExternal(&oldtup));
Assert(!HeapTupleHasExternal(newtup));
need_toast = false;
}
else
need_toast = (HeapTupleHasExternal(&oldtup) ||
HeapTupleHasExternal(newtup) ||
newtup->t_len > TOAST_TUPLE_THRESHOLD);
pagefree = PageGetHeapFreeSpace(page);
newtupsize = MAXALIGN(newtup->t_len);
if (need_toast || newtupsize > pagefree)
{
/* Clear obsolete visibility flags ... */
oldtup.t_data->t_infomask &= ~(HEAP_XMAX_COMMITTED |
HEAP_XMAX_INVALID |
HEAP_XMAX_IS_MULTI |
HEAP_IS_LOCKED |
HEAP_MOVED);
HeapTupleClearHotUpdated(&oldtup);
/* ... and store info about transaction updating this tuple */
HeapTupleHeaderSetXmax(oldtup.t_data, xid);
HeapTupleHeaderSetCmax(oldtup.t_data, cid, iscombo);
/* temporarily make it look not-updated */
oldtup.t_data->t_ctid = oldtup.t_self;
already_marked = true;
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
/*
* Let the toaster do its thing, if needed.
*
* Note: below this point, heaptup is the data we actually intend to
* store into the relation; newtup is the caller's original untoasted
* data.
*/
if (need_toast)
{
/* Note we always use WAL and FSM during updates */
heaptup = toast_insert_or_update(relation, newtup, &oldtup, 0);
newtupsize = MAXALIGN(heaptup->t_len);
}
else
heaptup = newtup;
/*
* Now, do we need a new page for the tuple, or not? This is a bit
* tricky since someone else could have added tuples to the page while
* we weren't looking. We have to recheck the available space after
* reacquiring the buffer lock. But don't bother to do that if the
* former amount of free space is still not enough; it's unlikely
* there's more free now than before.
*
* What's more, if we need to get a new page, we will need to acquire
* buffer locks on both old and new pages. To avoid deadlock against
* some other backend trying to get the same two locks in the other
* order, we must be consistent about the order we get the locks in.
* We use the rule "lock the lower-numbered page of the relation
* first". To implement this, we must do RelationGetBufferForTuple
* while not holding the lock on the old page, and we must rely on it
* to get the locks on both pages in the correct order.
*/
if (newtupsize > pagefree)
{
/* Assume there's no chance to put heaptup on same page. */
newbuf = RelationGetBufferForTuple(relation, heaptup->t_len,
buffer, 0, NULL,
&vmbuffer_new, &vmbuffer);
}
else
{
/* Re-acquire the lock on the old tuple's page. */
LockBuffer(buffer, BUFFER_LOCK_EXCLUSIVE);
/* Re-check using the up-to-date free space */
pagefree = PageGetHeapFreeSpace(page);
if (newtupsize > pagefree)
{
/*
* Rats, it doesn't fit anymore. We must now unlock and
* relock to avoid deadlock. Fortunately, this path should
* seldom be taken.
*/
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
newbuf = RelationGetBufferForTuple(relation, heaptup->t_len,
buffer, 0, NULL,
&vmbuffer_new, &vmbuffer);
}
else
{
/* OK, it fits here, so we're done. */
newbuf = buffer;
}
}
}
else
{
/* No TOAST work needed, and it'll fit on same page */
already_marked = false;
newbuf = buffer;
heaptup = newtup;
}
/*
* We're about to create the new tuple -- check for conflict first, to
* avoid possibly having to roll back work we've just done.
*
* NOTE: For a tuple insert, we only need to check for table locks, since
* predicate locking at the index level will cover ranges for anything
* except a table scan. Therefore, only provide the relation.
*/
CheckForSerializableConflictIn(relation, NULL, InvalidBuffer);
/*
* At this point newbuf and buffer are both pinned and locked, and newbuf
* has enough space for the new tuple. If they are the same buffer, only
* one pin is held.
*/
if (newbuf == buffer)
{
/*
* Since the new tuple is going into the same page, we might be able
* to do a HOT update. Check if any of the index columns have been
* changed. If not, then HOT update is possible.
*/
if (HeapSatisfiesHOTUpdate(relation, hot_attrs, &oldtup, heaptup))
use_hot_update = true;
}
else
{
/* Set a hint that the old page could use prune/defrag */
PageSetFull(page);
}
/* NO EREPORT(ERROR) from here till changes are logged */
START_CRIT_SECTION();
/*
* If this transaction commits, the old tuple will become DEAD sooner or
* later. Set flag that this page is a candidate for pruning once our xid
* falls below the OldestXmin horizon. If the transaction finally aborts,
* the subsequent page pruning will be a no-op and the hint will be
* cleared.
*
* XXX Should we set hint on newbuf as well? If the transaction aborts,
* there would be a prunable tuple in the newbuf; but for now we choose
* not to optimize for aborts. Note that heap_xlog_update must be kept in
* sync if this decision changes.
*/
PageSetPrunable(page, xid);
if (use_hot_update)
{
/* Mark the old tuple as HOT-updated */
HeapTupleSetHotUpdated(&oldtup);
/* And mark the new tuple as heap-only */
HeapTupleSetHeapOnly(heaptup);
/* Mark the caller's copy too, in case different from heaptup */
HeapTupleSetHeapOnly(newtup);
}
else
{
/* Make sure tuples are correctly marked as not-HOT */
HeapTupleClearHotUpdated(&oldtup);
HeapTupleClearHeapOnly(heaptup);
HeapTupleClearHeapOnly(newtup);
}
RelationPutHeapTuple(relation, newbuf, heaptup); /* insert new tuple */
if (!already_marked)
{
/* Clear obsolete visibility flags ... */
oldtup.t_data->t_infomask &= ~(HEAP_XMAX_COMMITTED |
HEAP_XMAX_INVALID |
HEAP_XMAX_IS_MULTI |
HEAP_IS_LOCKED |
HEAP_MOVED);
/* ... and store info about transaction updating this tuple */
HeapTupleHeaderSetXmax(oldtup.t_data, xid);
HeapTupleHeaderSetCmax(oldtup.t_data, cid, iscombo);
}
/* record address of new tuple in t_ctid of old one */
oldtup.t_data->t_ctid = heaptup->t_self;
/* clear PD_ALL_VISIBLE flags */
if (PageIsAllVisible(BufferGetPage(buffer)))
{
all_visible_cleared = true;
PageClearAllVisible(BufferGetPage(buffer));
visibilitymap_clear(relation, BufferGetBlockNumber(buffer),
vmbuffer);
}
if (newbuf != buffer && PageIsAllVisible(BufferGetPage(newbuf)))
{
all_visible_cleared_new = true;
PageClearAllVisible(BufferGetPage(newbuf));
visibilitymap_clear(relation, BufferGetBlockNumber(newbuf),
vmbuffer_new);
}
if (newbuf != buffer)
MarkBufferDirty(newbuf);
MarkBufferDirty(buffer);
/* XLOG stuff */
if (RelationNeedsWAL(relation))
{
XLogRecPtr recptr = log_heap_update(relation, buffer, oldtup.t_self,
newbuf, heaptup,
all_visible_cleared,
all_visible_cleared_new);
if (newbuf != buffer)
{
PageSetLSN(BufferGetPage(newbuf), recptr);
PageSetTLI(BufferGetPage(newbuf), ThisTimeLineID);
}
PageSetLSN(BufferGetPage(buffer), recptr);
PageSetTLI(BufferGetPage(buffer), ThisTimeLineID);
}
END_CRIT_SECTION();
if (newbuf != buffer)
LockBuffer(newbuf, BUFFER_LOCK_UNLOCK);
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
/*
* Mark old tuple for invalidation from system caches at next command
* boundary, and mark the new tuple for invalidation in case we abort.
* We have to do this before releasing the buffer because oldtup is in
* the buffer. (heaptup is all in local memory, but it's necessary to
* process both tuple versions in one call to inval.c so we can avoid
* redundant sinval messages.)
*/
CacheInvalidateHeapTuple(relation, &oldtup, heaptup);
/* Now we can release the buffer(s) */
if (newbuf != buffer)
ReleaseBuffer(newbuf);
ReleaseBuffer(buffer);
if (BufferIsValid(vmbuffer_new))
ReleaseBuffer(vmbuffer_new);
if (BufferIsValid(vmbuffer))
ReleaseBuffer(vmbuffer);
/*
* Release the lmgr tuple lock, if we had it.
*/
if (have_tuple_lock)
UnlockTuple(relation, &(oldtup.t_self), ExclusiveLock);
pgstat_count_heap_update(relation, use_hot_update);
/*
* If heaptup is a private copy, release it. Don't forget to copy t_self
* back to the caller's image, too.
*/
if (heaptup != newtup)
{
newtup->t_self = heaptup->t_self;
heap_freetuple(heaptup);
}
bms_free(hot_attrs);
return HeapTupleMayBeUpdated;
}
/*
* Check if the specified attribute's value is same in both given tuples.
* Subroutine for HeapSatisfiesHOTUpdate.
*/
static bool
heap_tuple_attr_equals(TupleDesc tupdesc, int attrnum,
HeapTuple tup1, HeapTuple tup2)
{
Datum value1,
value2;
bool isnull1,
isnull2;
Form_pg_attribute att;
/*
* If it's a whole-tuple reference, say "not equal". It's not really
* worth supporting this case, since it could only succeed after a no-op
* update, which is hardly a case worth optimizing for.
*/
if (attrnum == 0)
return false;
/*
* Likewise, automatically say "not equal" for any system attribute other
* than OID and tableOID; we cannot expect these to be consistent in a HOT
* chain, or even to be set correctly yet in the new tuple.
*/
if (attrnum < 0)
{
if (attrnum != ObjectIdAttributeNumber &&
attrnum != TableOidAttributeNumber)
return false;
}
/*
* Extract the corresponding values. XXX this is pretty inefficient if
* there are many indexed columns. Should HeapSatisfiesHOTUpdate do a
* single heap_deform_tuple call on each tuple, instead? But that doesn't
* work for system columns ...
*/
value1 = heap_getattr(tup1, attrnum, tupdesc, &isnull1);
value2 = heap_getattr(tup2, attrnum, tupdesc, &isnull2);
/*
* If one value is NULL and other is not, then they are certainly not
* equal
*/
if (isnull1 != isnull2)
return false;
/*
* If both are NULL, they can be considered equal.
*/
if (isnull1)
return true;
/*
* We do simple binary comparison of the two datums. This may be overly
* strict because there can be multiple binary representations for the
* same logical value. But we should be OK as long as there are no false
* positives. Using a type-specific equality operator is messy because
* there could be multiple notions of equality in different operator
* classes; furthermore, we cannot safely invoke user-defined functions
* while holding exclusive buffer lock.
*/
if (attrnum <= 0)
{
/* The only allowed system columns are OIDs, so do this */
return (DatumGetObjectId(value1) == DatumGetObjectId(value2));
}
else
{
Assert(attrnum <= tupdesc->natts);
att = tupdesc->attrs[attrnum - 1];
return datumIsEqual(value1, value2, att->attbyval, att->attlen);
}
}
/*
* Check if the old and new tuples represent a HOT-safe update. To be able
* to do a HOT update, we must not have changed any columns used in index
* definitions.
*
* The set of attributes to be checked is passed in (we dare not try to
* compute it while holding exclusive buffer lock...) NOTE that hot_attrs
* is destructively modified! That is OK since this is invoked at most once
* by heap_update().
*
* Returns true if safe to do HOT update.
*/
static bool
HeapSatisfiesHOTUpdate(Relation relation, Bitmapset *hot_attrs,
HeapTuple oldtup, HeapTuple newtup)
{
int attrnum;
while ((attrnum = bms_first_member(hot_attrs)) >= 0)
{
/* Adjust for system attributes */
attrnum += FirstLowInvalidHeapAttributeNumber;
/* If the attribute value has changed, we can't do HOT update */
if (!heap_tuple_attr_equals(RelationGetDescr(relation), attrnum,
oldtup, newtup))
return false;
}
return true;
}
/*
* simple_heap_update - replace a tuple
*
* This routine may be used to update a tuple when concurrent updates of
* the target tuple are not expected (for example, because we have a lock
* on the relation associated with the tuple). Any failure is reported
* via ereport().
*/
void
simple_heap_update(Relation relation, ItemPointer otid, HeapTuple tup)
{
HTSU_Result result;
ItemPointerData update_ctid;
TransactionId update_xmax;
result = heap_update(relation, otid, tup,
&update_ctid, &update_xmax,
GetCurrentCommandId(true), InvalidSnapshot,
true /* wait for commit */ );
switch (result)
{
case HeapTupleSelfUpdated:
/* Tuple was already updated in current command? */
elog(ERROR, "tuple already updated by self");
break;
case HeapTupleMayBeUpdated:
/* done successfully */
break;
case HeapTupleUpdated:
elog(ERROR, "tuple concurrently updated");
break;
default:
elog(ERROR, "unrecognized heap_update status: %u", result);
break;
}
}
/*
* heap_lock_tuple - lock a tuple in shared or exclusive mode
*
* Note that this acquires a buffer pin, which the caller must release.
*
* Input parameters:
* relation: relation containing tuple (caller must hold suitable lock)
* tuple->t_self: TID of tuple to lock (rest of struct need not be valid)
* cid: current command ID (used for visibility test, and stored into
* tuple's cmax if lock is successful)
* mode: indicates if shared or exclusive tuple lock is desired
* nowait: if true, ereport rather than blocking if lock not available
*
* Output parameters:
* *tuple: all fields filled in
* *buffer: set to buffer holding tuple (pinned but not locked at exit)
* *ctid: set to tuple's t_ctid, but only in failure cases
* *update_xmax: set to tuple's xmax, but only in failure cases
*
* Function result may be:
* HeapTupleMayBeUpdated: lock was successfully acquired
* HeapTupleSelfUpdated: lock failed because tuple updated by self
* HeapTupleUpdated: lock failed because tuple updated by other xact
*
* In the failure cases, the routine returns the tuple's t_ctid and t_xmax.
* If t_ctid is the same as t_self, the tuple was deleted; if different, the
* tuple was updated, and t_ctid is the location of the replacement tuple.
* (t_xmax is needed to verify that the replacement tuple matches.)
*
*
* NOTES: because the shared-memory lock table is of finite size, but users
* could reasonably want to lock large numbers of tuples, we do not rely on
* the standard lock manager to store tuple-level locks over the long term.
* Instead, a tuple is marked as locked by setting the current transaction's
* XID as its XMAX, and setting additional infomask bits to distinguish this
* usage from the more normal case of having deleted the tuple. When
* multiple transactions concurrently share-lock a tuple, the first locker's
* XID is replaced in XMAX with a MultiTransactionId representing the set of
* XIDs currently holding share-locks.
*
* When it is necessary to wait for a tuple-level lock to be released, the
* basic delay is provided by XactLockTableWait or MultiXactIdWait on the
* contents of the tuple's XMAX. However, that mechanism will release all
* waiters concurrently, so there would be a race condition as to which
* waiter gets the tuple, potentially leading to indefinite starvation of
* some waiters. The possibility of share-locking makes the problem much
* worse --- a steady stream of share-lockers can easily block an exclusive
* locker forever. To provide more reliable semantics about who gets a
* tuple-level lock first, we use the standard lock manager. The protocol
* for waiting for a tuple-level lock is really
* LockTuple()
* XactLockTableWait()
* mark tuple as locked by me
* UnlockTuple()
* When there are multiple waiters, arbitration of who is to get the lock next
* is provided by LockTuple(). However, at most one tuple-level lock will
* be held or awaited per backend at any time, so we don't risk overflow
* of the lock table. Note that incoming share-lockers are required to
* do LockTuple as well, if there is any conflict, to ensure that they don't
* starve out waiting exclusive-lockers. However, if there is not any active
* conflict for a tuple, we don't incur any extra overhead.
*/
HTSU_Result
heap_lock_tuple(Relation relation, HeapTuple tuple, Buffer *buffer,
ItemPointer ctid, TransactionId *update_xmax,
CommandId cid, LockTupleMode mode, bool nowait)
{
HTSU_Result result;
ItemPointer tid = &(tuple->t_self);
ItemId lp;
Page page;
TransactionId xid;
TransactionId xmax;
uint16 old_infomask;
uint16 new_infomask;
LOCKMODE tuple_lock_type;
bool have_tuple_lock = false;
tuple_lock_type = (mode == LockTupleShared) ? ShareLock : ExclusiveLock;
*buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid));
LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
page = BufferGetPage(*buffer);
lp = PageGetItemId(page, ItemPointerGetOffsetNumber(tid));
Assert(ItemIdIsNormal(lp));
tuple->t_data = (HeapTupleHeader) PageGetItem(page, lp);
tuple->t_len = ItemIdGetLength(lp);
tuple->t_tableOid = RelationGetRelid(relation);
l3:
result = HeapTupleSatisfiesUpdate(tuple->t_data, cid, *buffer);
if (result == HeapTupleInvisible)
{
UnlockReleaseBuffer(*buffer);
elog(ERROR, "attempted to lock invisible tuple");
}
else if (result == HeapTupleBeingUpdated)
{
TransactionId xwait;
uint16 infomask;
/* must copy state data before unlocking buffer */
xwait = HeapTupleHeaderGetXmax(tuple->t_data);
infomask = tuple->t_data->t_infomask;
LockBuffer(*buffer, BUFFER_LOCK_UNLOCK);
/*
* If we wish to acquire share lock, and the tuple is already
* share-locked by a multixact that includes any subtransaction of the
* current top transaction, then we effectively hold the desired lock
* already. We *must* succeed without trying to take the tuple lock,
* else we will deadlock against anyone waiting to acquire exclusive
* lock. We don't need to make any state changes in this case.
*/
if (mode == LockTupleShared &&
(infomask & HEAP_XMAX_IS_MULTI) &&
MultiXactIdIsCurrent((MultiXactId) xwait))
{
Assert(infomask & HEAP_XMAX_SHARED_LOCK);
/* Probably can't hold tuple lock here, but may as well check */
if (have_tuple_lock)
UnlockTuple(relation, tid, tuple_lock_type);
return HeapTupleMayBeUpdated;
}
/*
* Acquire tuple lock to establish our priority for the tuple.
* LockTuple will release us when we are next-in-line for the tuple.
* We must do this even if we are share-locking.
*
* If we are forced to "start over" below, we keep the tuple lock;
* this arranges that we stay at the head of the line while rechecking
* tuple state.
*/
if (!have_tuple_lock)
{
if (nowait)
{
if (!ConditionalLockTuple(relation, tid, tuple_lock_type))
ereport(ERROR,
(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
errmsg("could not obtain lock on row in relation \"%s\"",
RelationGetRelationName(relation))));
}
else
LockTuple(relation, tid, tuple_lock_type);
have_tuple_lock = true;
}
if (mode == LockTupleShared && (infomask & HEAP_XMAX_SHARED_LOCK))
{
/*
* Acquiring sharelock when there's at least one sharelocker
* already. We need not wait for him/them to complete.
*/
LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
/*
* Make sure it's still a shared lock, else start over. (It's OK
* if the ownership of the shared lock has changed, though.)
*/
if (!(tuple->t_data->t_infomask & HEAP_XMAX_SHARED_LOCK))
goto l3;
}
else if (infomask & HEAP_XMAX_IS_MULTI)
{
/* wait for multixact to end */
if (nowait)
{
if (!ConditionalMultiXactIdWait((MultiXactId) xwait))
ereport(ERROR,
(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
errmsg("could not obtain lock on row in relation \"%s\"",
RelationGetRelationName(relation))));
}
else
MultiXactIdWait((MultiXactId) xwait);
LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
/*
* If xwait had just locked the tuple then some other xact could
* update this tuple before we get to this point. Check for xmax
* change, and start over if so.
*/
if (!(tuple->t_data->t_infomask & HEAP_XMAX_IS_MULTI) ||
!TransactionIdEquals(HeapTupleHeaderGetXmax(tuple->t_data),
xwait))
goto l3;
/*
* You might think the multixact is necessarily done here, but not
* so: it could have surviving members, namely our own xact or
* other subxacts of this backend. It is legal for us to lock the
* tuple in either case, however. We don't bother changing the
* on-disk hint bits since we are about to overwrite the xmax
* altogether.
*/
}
else
{
/* wait for regular transaction to end */
if (nowait)
{
if (!ConditionalXactLockTableWait(xwait))
ereport(ERROR,
(errcode(ERRCODE_LOCK_NOT_AVAILABLE),
errmsg("could not obtain lock on row in relation \"%s\"",
RelationGetRelationName(relation))));
}
else
XactLockTableWait(xwait);
LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
/*
* xwait is done, but if xwait had just locked the tuple then some
* other xact could update this tuple before we get to this point.
* Check for xmax change, and start over if so.
*/
if ((tuple->t_data->t_infomask & HEAP_XMAX_IS_MULTI) ||
!TransactionIdEquals(HeapTupleHeaderGetXmax(tuple->t_data),
xwait))
goto l3;
/* Otherwise check if it committed or aborted */
UpdateXmaxHintBits(tuple->t_data, *buffer, xwait);
}
/*
* We may lock if previous xmax aborted, or if it committed but only
* locked the tuple without updating it. The case where we didn't
* wait because we are joining an existing shared lock is correctly
* handled, too.
*/
if (tuple->t_data->t_infomask & (HEAP_XMAX_INVALID |
HEAP_IS_LOCKED))
result = HeapTupleMayBeUpdated;
else
result = HeapTupleUpdated;
}
if (result != HeapTupleMayBeUpdated)
{
Assert(result == HeapTupleSelfUpdated || result == HeapTupleUpdated);
Assert(!(tuple->t_data->t_infomask & HEAP_XMAX_INVALID));
*ctid = tuple->t_data->t_ctid;
*update_xmax = HeapTupleHeaderGetXmax(tuple->t_data);
LockBuffer(*buffer, BUFFER_LOCK_UNLOCK);
if (have_tuple_lock)
UnlockTuple(relation, tid, tuple_lock_type);
return result;
}
/*
* We might already hold the desired lock (or stronger), possibly under a
* different subtransaction of the current top transaction. If so, there
* is no need to change state or issue a WAL record. We already handled
* the case where this is true for xmax being a MultiXactId, so now check
* for cases where it is a plain TransactionId.
*
* Note in particular that this covers the case where we already hold
* exclusive lock on the tuple and the caller only wants shared lock. It
* would certainly not do to give up the exclusive lock.
*/
xmax = HeapTupleHeaderGetXmax(tuple->t_data);
old_infomask = tuple->t_data->t_infomask;
if (!(old_infomask & (HEAP_XMAX_INVALID |
HEAP_XMAX_COMMITTED |
HEAP_XMAX_IS_MULTI)) &&
(mode == LockTupleShared ?
(old_infomask & HEAP_IS_LOCKED) :
(old_infomask & HEAP_XMAX_EXCL_LOCK)) &&
TransactionIdIsCurrentTransactionId(xmax))
{
LockBuffer(*buffer, BUFFER_LOCK_UNLOCK);
/* Probably can't hold tuple lock here, but may as well check */
if (have_tuple_lock)
UnlockTuple(relation, tid, tuple_lock_type);
return HeapTupleMayBeUpdated;
}
/*
* Compute the new xmax and infomask to store into the tuple. Note we do
* not modify the tuple just yet, because that would leave it in the wrong
* state if multixact.c elogs.
*/
xid = GetCurrentTransactionId();
new_infomask = old_infomask & ~(HEAP_XMAX_COMMITTED |
HEAP_XMAX_INVALID |
HEAP_XMAX_IS_MULTI |
HEAP_IS_LOCKED |
HEAP_MOVED);
if (mode == LockTupleShared)
{
/*
* If this is the first acquisition of a shared lock in the current
* transaction, set my per-backend OldestMemberMXactId setting. We can
* be certain that the transaction will never become a member of any
* older MultiXactIds than that. (We have to do this even if we end
* up just using our own TransactionId below, since some other backend
* could incorporate our XID into a MultiXact immediately afterwards.)
*/
MultiXactIdSetOldestMember();
new_infomask |= HEAP_XMAX_SHARED_LOCK;
/*
* Check to see if we need a MultiXactId because there are multiple
* lockers.
*
* HeapTupleSatisfiesUpdate will have set the HEAP_XMAX_INVALID bit if
* the xmax was a MultiXactId but it was not running anymore. There is
* a race condition, which is that the MultiXactId may have finished
* since then, but that uncommon case is handled within
* MultiXactIdExpand.
*
* There is a similar race condition possible when the old xmax was a
* regular TransactionId. We test TransactionIdIsInProgress again
* just to narrow the window, but it's still possible to end up
* creating an unnecessary MultiXactId. Fortunately this is harmless.
*/
if (!(old_infomask & (HEAP_XMAX_INVALID | HEAP_XMAX_COMMITTED)))
{
if (old_infomask & HEAP_XMAX_IS_MULTI)
{
/*
* If the XMAX is already a MultiXactId, then we need to
* expand it to include our own TransactionId.
*/
xid = MultiXactIdExpand((MultiXactId) xmax, xid);
new_infomask |= HEAP_XMAX_IS_MULTI;
}
else if (TransactionIdIsInProgress(xmax))
{
/*
* If the XMAX is a valid TransactionId, then we need to
* create a new MultiXactId that includes both the old locker
* and our own TransactionId.
*/
xid = MultiXactIdCreate(xmax, xid);
new_infomask |= HEAP_XMAX_IS_MULTI;
}
else
{
/*
* Can get here iff HeapTupleSatisfiesUpdate saw the old xmax
* as running, but it finished before
* TransactionIdIsInProgress() got to run. Treat it like
* there's no locker in the tuple.
*/
}
}
else
{
/*
* There was no previous locker, so just insert our own
* TransactionId.
*/
}
}
else
{
/* We want an exclusive lock on the tuple */
new_infomask |= HEAP_XMAX_EXCL_LOCK;
}
START_CRIT_SECTION();
/*
* Store transaction information of xact locking the tuple.
*
* Note: Cmax is meaningless in this context, so don't set it; this avoids
* possibly generating a useless combo CID.
*/
tuple->t_data->t_infomask = new_infomask;
HeapTupleHeaderClearHotUpdated(tuple->t_data);
HeapTupleHeaderSetXmax(tuple->t_data, xid);
/* Make sure there is no forward chain link in t_ctid */
tuple->t_data->t_ctid = *tid;
MarkBufferDirty(*buffer);
/*
* XLOG stuff. You might think that we don't need an XLOG record because
* there is no state change worth restoring after a crash. You would be
* wrong however: we have just written either a TransactionId or a
* MultiXactId that may never have been seen on disk before, and we need
* to make sure that there are XLOG entries covering those ID numbers.
* Else the same IDs might be re-used after a crash, which would be
* disastrous if this page made it to disk before the crash. Essentially
* we have to enforce the WAL log-before-data rule even in this case.
* (Also, in a PITR log-shipping or 2PC environment, we have to have XLOG
* entries for everything anyway.)
*/
if (RelationNeedsWAL(relation))
{
xl_heap_lock xlrec;
XLogRecPtr recptr;
XLogRecData rdata[2];
xlrec.target.node = relation->rd_node;
xlrec.target.tid = tuple->t_self;
xlrec.locking_xid = xid;
xlrec.xid_is_mxact = ((new_infomask & HEAP_XMAX_IS_MULTI) != 0);
xlrec.shared_lock = (mode == LockTupleShared);
rdata[0].data = (char *) &xlrec;
rdata[0].len = SizeOfHeapLock;
rdata[0].buffer = InvalidBuffer;
rdata[0].next = &(rdata[1]);
rdata[1].data = NULL;
rdata[1].len = 0;
rdata[1].buffer = *buffer;
rdata[1].buffer_std = true;
rdata[1].next = NULL;
recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_LOCK, rdata);
PageSetLSN(page, recptr);
PageSetTLI(page, ThisTimeLineID);
}