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MDEV-16678 Prefer MDL to dict_sys.latch for innodb background tasks 
This is joint work with Thirunarayanan Balathandayuthapani.
The MDL interface between InnoDB and the rest of the server
(in storage/innobase/dict/dict0dict.cc and in include/)
is my work, while most everything else is Thiru's.

The collection of InnoDB persistent statistics and the
defragmentation were not refactored to use MDL. They will
keep relying on lower-level interlocking with
fil_check_pending_operations().

The purge of transaction history and the background operations on
fulltext indexes will use MDL. We will revert
commit 2c4844c
(MDEV-17813) because thanks to MDL, purge cannot conflict
with DDL operations anymore. For a similar reason, we will remove
the MDEV-16222 test case from gcol.innodb_virtual_debug_purge.

Purge is essentially replacing all use of the global dict_sys.latch
with MDL. Purge will skip the undo log records for tables whose names
start with #sql-ib or #sql2. Theoretically, such tables might
be renamed back to visible table names if TRUNCATE fails to
create a new table, or the final rename in ALTER TABLE...ALGORITHM=COPY
fails. In that case, purge could permanently leave some garbage
in the table. Such garbage will be tolerated; the table would not
be considered corrupted.

To avoid repeated MDL releases and acquisitions,
trx_purge_attach_undo_recs() will sort undo log records by table_id,
and purge_node_t will keep the MDL and table handle open for multiple
successive undo log records.

get_purge_table(): A new accessor, used during the purge of
history for indexed virtual columns. This interface should ideally
not exist at all.

thd_mdl_context(): Accessor of THD::mdl_context.
Wrapped in a new thd_mdl_service.

dict_get_db_name_len(): Define inline.

dict_acquire_mdl_shared(): Acquire explicit shared MDL on a table name
if needed.

dict_table_open_on_id(): Return MDL_ticket, if requested.

dict_table_close(): Release MDL ticket, if requested.

dict_fts_index_syncing(), dict_index_t::index_fts_syncing: Remove.
row_drop_table_for_mysql() no longer needs to check these, because
MDL guarantees that a fulltext index sync will not be in progress
while MDL_EXCLUSIVE is protecting a DDL operation.

dict_table_t::parse_name(): Parse the table name for acquiring MDL.

purge_node_t::undo_recs: Change the type to std::list<trx_purge_rec_t*>
(different container, and storing also roll_ptr).

purge_node_t: Add mdl_ticket, last_table_id, purge_thd, mdl_hold_recs
for acquiring MDL and for keeping the table open across multiple
undo log records.

purge_vcol_info_t, row_purge_store_vsec_cur(), row_purge_restore_vsec_cur():
Remove. We will acquire the MDL earlier.

purge_sys_t::heap: Added, for reading undo log records.

fts_sync_during_ddl(): Invoked during ALGORITHM=INPLACE operations
to ensure that fts_sync_table() will not conflict with MDL_EXCLUSIVE.
Uses fts_t::sync_message for bookkeeping.
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dr-m committed Dec 10, 2019
1 parent e47bd00 commit ea37b14
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Showing 29 changed files with 693 additions and 976 deletions.
46 include/mysql/service_thd_mdl.h
View file
@@ -0,0 +1,46 @@
/* Copyright (c) 2019, MariaDB Corporation.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */

#pragma once

/**
@file include/mysql/service_thd_mdl.h
This service provides functions for plugins and storage engines to access
metadata locks.
*/

#ifdef __cplusplus
extern "C" {
#endif


extern struct thd_mdl_service_st {
void *(*thd_mdl_context)(MYSQL_THD);
} *thd_mdl_service;

#ifdef MYSQL_DYNAMIC_PLUGIN
# define thd_mdl_context(_THD) thd_mdl_service->thd_mdl_context(_THD)
#else
/**
MDL_context accessor
@param thd the current session
@return pointer to thd->mdl_context
*/
void *thd_mdl_context(MYSQL_THD thd);
#endif

#ifdef __cplusplus
}
#endif
3 include/service_versions.h
View file
@@ -1,5 +1,5 @@
/* Copyright (c) 2009, 2010, Oracle and/or its affiliates.
Copyright (c) 2012, 2017, MariaDB
Copyright (c) 2012, 2019, MariaDB
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
@@ -43,3 +43,4 @@
#define VERSION_thd_wait 0x0100
#define VERSION_wsrep 0x0202
#define VERSION_json 0x0100
#define VERSION_thd_mdl 0x0100
27 mysql-test/suite/gcol/r/innodb_virtual_debug_purge.result
View file
@@ -204,32 +204,5 @@ connection truncate;
disconnect truncate;
connection default;
DROP TABLE t1, t2;
#
# MDEV-16222 Assertion `0' failed in row_purge_remove_sec_if_poss_leaf
# on table with virtual columns and indexes
#
set @saved_dbug= @@global.debug_dbug;
set global debug_dbug= "+d,ib_purge_virtual_mdev_16222_1,ib_purge_virtual_mdev_16222_2";
create table t1 (
pk serial, vb tinyblob as (b) virtual, b tinyblob,
primary key(pk), index (vb(64)))
engine innodb;
insert ignore into t1 (b) values ('foo');
select * into outfile 'load.data' from t1;
load data infile 'load.data' replace into table t1;
set debug_sync= "now WAIT_FOR latch_released";
set global debug_dbug= "-d,ib_purge_virtual_mdev_16222_1";
drop table t1;
set debug_sync= "now SIGNAL drop_started WAIT_FOR got_no_such_table";
create table t1 (
pk serial, vb tinyblob as (b) virtual, b tinyblob,
primary key(pk), index (vb(64)))
engine innodb;
insert ignore into t1 (b) values ('foo');
select * into outfile 'load.data' from t1;
load data infile 'load.data' replace into table t1;
set debug_sync= "now WAIT_FOR got_no_such_table";
set global debug_dbug= @saved_dbug;
drop table t1;
set debug_sync=reset;
SET GLOBAL innodb_purge_rseg_truncate_frequency = @saved_frequency;
48 mysql-test/suite/gcol/t/innodb_virtual_debug_purge.test
View file
@@ -259,54 +259,6 @@ disconnect truncate;
connection default;
DROP TABLE t1, t2;

--echo #
--echo # MDEV-16222 Assertion `0' failed in row_purge_remove_sec_if_poss_leaf
--echo # on table with virtual columns and indexes
--echo #

--let $datadir= `select @@datadir`
set @saved_dbug= @@global.debug_dbug;
set global debug_dbug= "+d,ib_purge_virtual_mdev_16222_1,ib_purge_virtual_mdev_16222_2";

create table t1 (
pk serial, vb tinyblob as (b) virtual, b tinyblob,
primary key(pk), index (vb(64)))
engine innodb;

insert ignore into t1 (b) values ('foo');

select * into outfile 'load.data' from t1;
load data infile 'load.data' replace into table t1;

set debug_sync= "now WAIT_FOR latch_released";
set global debug_dbug= "-d,ib_purge_virtual_mdev_16222_1";
drop table t1;
--remove_file $datadir/test/load.data

set debug_sync= "now SIGNAL drop_started WAIT_FOR got_no_such_table";

create table t1 (
pk serial, vb tinyblob as (b) virtual, b tinyblob,
primary key(pk), index (vb(64)))
engine innodb;

insert ignore into t1 (b) values ('foo');

select * into outfile 'load.data' from t1;
load data infile 'load.data' replace into table t1;

set debug_sync= "now WAIT_FOR got_no_such_table";

# FIXME: Race condition here:
# 1. purge thread goes into sending got_no_such_table
# 2. test thread finishes debug_sync= "RESET" below
# 3. purge thread sends got_no_such_table
set global debug_dbug= @saved_dbug;

# cleanup
drop table t1;
--remove_file $datadir/test/load.data

--source include/wait_until_count_sessions.inc
set debug_sync=reset;
SET GLOBAL innodb_purge_rseg_truncate_frequency = @saved_frequency;
22 mysql-test/suite/innodb/r/instant_alter_purge.result
View file
@@ -21,26 +21,4 @@ ALTER TABLE t1 DROP extra;
disconnect prevent_purge;
InnoDB 0 transactions not purged
DROP TABLE t1;
#
# MDEV-17813 Crash in instant ALTER TABLE due to purge
# concurrently emptying table
#
CREATE TABLE t1 (f2 INT) ENGINE=InnoDB;
INSERT INTO t1 SET f2=1;
ALTER TABLE t1 ADD COLUMN f1 INT;
connect purge_control,localhost,root;
START TRANSACTION WITH CONSISTENT SNAPSHOT;
connection default;
DELETE FROM t1;
SET DEBUG_SYNC='innodb_commit_inplace_alter_table_enter SIGNAL go WAIT_FOR do';
ALTER TABLE t1 ADD COLUMN f3 INT;
connection purge_control;
SET DEBUG_SYNC='now WAIT_FOR go';
COMMIT;
InnoDB 0 transactions not purged
SET DEBUG_SYNC='now SIGNAL do';
disconnect purge_control;
connection default;
SET DEBUG_SYNC=RESET;
DROP TABLE t1;
SET GLOBAL innodb_purge_rseg_truncate_frequency = @saved_frequency;
2 mysql-test/suite/innodb/r/row_format_redundant.result
View file
@@ -76,7 +76,7 @@ DROP TABLE t1;
Warnings:
Warning 1932 Table 'test.t1' doesn't exist in engine
DROP TABLE t2,t3;
FOUND 50 /\[ERROR\] InnoDB: Table `test`\.`t1` in InnoDB data dictionary contains invalid flags\. SYS_TABLES\.TYPE=1 SYS_TABLES\.MIX_LEN=511\b/ in mysqld.1.err
FOUND 49 /\[ERROR\] InnoDB: Table `test`\.`t1` in InnoDB data dictionary contains invalid flags\. SYS_TABLES\.TYPE=1 SYS_TABLES\.MIX_LEN=511\b/ in mysqld.1.err
# restart
ib_buffer_pool
ib_logfile0
38 mysql-test/suite/innodb/t/instant_alter_purge.test
View file
@@ -34,42 +34,4 @@ disconnect prevent_purge;
let $wait_all_purged= 0;
--source include/wait_all_purged.inc
DROP TABLE t1;

--echo #
--echo # MDEV-17813 Crash in instant ALTER TABLE due to purge
--echo # concurrently emptying table
--echo #
CREATE TABLE t1 (f2 INT) ENGINE=InnoDB;
INSERT INTO t1 SET f2=1;
ALTER TABLE t1 ADD COLUMN f1 INT;

connect (purge_control,localhost,root);
START TRANSACTION WITH CONSISTENT SNAPSHOT;

connection default;
DELETE FROM t1;

if ($have_debug) {
SET DEBUG_SYNC='innodb_commit_inplace_alter_table_enter SIGNAL go WAIT_FOR do';
}
send ALTER TABLE t1 ADD COLUMN f3 INT;

connection purge_control;
if ($have_debug) {
SET DEBUG_SYNC='now WAIT_FOR go';
}
COMMIT;
--source include/wait_all_purged.inc
if ($have_debug) {
SET DEBUG_SYNC='now SIGNAL do';
}
disconnect purge_control;

connection default;
reap;
if ($have_debug) {
SET DEBUG_SYNC=RESET;
}
DROP TABLE t1;

SET GLOBAL innodb_purge_rseg_truncate_frequency = @saved_frequency;
18 sql/sql_class.cc
View file
@@ -4752,6 +4752,12 @@ TABLE *open_purge_table(THD *thd, const char *db, size_t dblen,
DBUG_RETURN(error ? NULL : tl->table);
}

TABLE *get_purge_table(THD *thd)
{
/* see above, at most one table can be opened */
DBUG_ASSERT(thd->open_tables == NULL || thd->open_tables->next == NULL);
return thd->open_tables;
}

/** Find an open table in the list of prelocked tabled
@@ -5303,6 +5309,18 @@ extern "C" void thd_wait_end(MYSQL_THD thd)

#endif // INNODB_COMPATIBILITY_HOOKS */


/**
MDL_context accessor
@param thd the current session
@return pointer to thd->mdl_context
*/
extern "C" void *thd_mdl_context(MYSQL_THD thd)
{
return &thd->mdl_context;
}


/****************************************************************************
Handling of statement states in functions and triggers.
11 sql/sql_plugin_services.ic
View file
@@ -1,5 +1,5 @@
/* Copyright (c) 2009, 2010, Oracle and/or its affiliates.
Copyright (c) 2012, 2014, Monty Program Ab
Copyright (c) 2012, 2019, MariaDB Corporation.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
@@ -17,6 +17,7 @@
/* support for Services */
#include <service_versions.h>
#include <mysql/service_wsrep.h>
#include <mysql/service_thd_mdl.h>

struct st_service_ref {
const char *name;
@@ -220,6 +221,11 @@ struct json_service_st json_handler=
json_unescape_json
};

static struct thd_mdl_service_st thd_mdl_handler=
{
thd_mdl_context
};

static struct st_service_ref list_of_services[]=
{
{ "base64_service", VERSION_base64, &base64_handler },
@@ -243,6 +249,7 @@ static struct st_service_ref list_of_services[]=
{ "thd_timezone_service", VERSION_thd_timezone, &thd_timezone_handler },
{ "thd_wait_service", VERSION_thd_wait, &thd_wait_handler },
{ "wsrep_service", VERSION_wsrep, &wsrep_handler },
{ "json_service", VERSION_json, &json_handler }
{ "json_service", VERSION_json, &json_handler },
{ "thd_mdl_service", VERSION_thd_mdl, &thd_mdl_handler }
};

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