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MDEV-26636: InnoDB defragmentation statistics cause races on TEMPORAR…
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…Y TABLE

btr_defragment_save_defrag_stats_if_needed(): Do not save
defragmentation statistics for temporary tables.
They are exempt of defragmentation anyway
(ha_innobase::optimize() never invokes defragmentation for them),
and the user-visible names are not available inside InnoDB.

Furthermore, InnoDB assumes that temporary tables are never accessed
by other threads than the one that handles the session with which
the temporary table is associated with.

Furthermore, we simplify the test innodb.innodb_defrag_stats
and include a test case that demonstrates that defragmentation
statistics are no longer being saved for temporary tables.
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@dr-m
dr-m committed Sep 18, 2021
1 parent 496d3dd commit 3209bc6
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103 changes: 36 additions & 67 deletions mysql-test/suite/innodb/r/innodb_defrag_stats.result
View file
Original file line number Diff line number Diff line change
@@ -1,22 +1,8 @@
DROP TABLE if exists t1;
select @@global.innodb_stats_persistent;
@@global.innodb_stats_persistent
0
set global innodb_defragment_stats_accuracy = 20;
SET GLOBAL innodb_defragment_stats_accuracy = 20;
DELETE FROM mysql.innodb_index_stats;
# Create table.
CREATE TABLE t1 (a INT NOT NULL PRIMARY KEY AUTO_INCREMENT, b VARCHAR(256), KEY SECOND(a, b)) ENGINE=INNODB;
# Populate data
INSERT INTO t1 VALUES(1, REPEAT('A', 256));
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 SELECT seq, REPEAT('A', 256) FROM seq_1_to_1024;
# Not enough page splits to trigger persistent stats write yet.
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_page_split');
count(stat_value) = 0
Expand All @@ -27,7 +13,7 @@ count(stat_value) = 0
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_leaf_pages_defrag');
count(stat_value) = 0
1
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 SELECT seq, REPEAT('A', 256) FROM seq_1025_to_2048;
# Persistent stats recorded.
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_page_split');
count(stat_value) > 0
Expand All @@ -39,6 +25,7 @@ select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like
count(stat_value) > 0
1
# Delete some rows.
BEGIN;
delete from t1 where a between 100 * 20 and 100 * 20 + 30;
delete from t1 where a between 100 * 19 and 100 * 19 + 30;
delete from t1 where a between 100 * 18 and 100 * 18 + 30;
Expand All @@ -59,8 +46,7 @@ delete from t1 where a between 100 * 4 and 100 * 4 + 30;
delete from t1 where a between 100 * 3 and 100 * 3 + 30;
delete from t1 where a between 100 * 2 and 100 * 2 + 30;
delete from t1 where a between 100 * 1 and 100 * 1 + 30;
# Server Restarted
# Confirm persistent stats still there after restart.
COMMIT;
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_page_split');
count(stat_value) > 0
1
Expand All @@ -73,9 +59,6 @@ count(stat_value) > 0
optimize table t1;
Table Op Msg_type Msg_text
test.t1 optimize status OK
select sleep(2);
sleep(2)
0
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_page_split');
count(stat_value) > 0
1
Expand Down Expand Up @@ -108,9 +91,6 @@ count(stat_value) > 0
1
# Table rename should cause stats rename.
rename table t1 to t2;
select sleep(1);
sleep(1)
0
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_page_split');
count(stat_value) = 0
1
Expand All @@ -129,47 +109,36 @@ count(stat_value) > 0
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t2%' and stat_name in ('n_leaf_pages_defrag');
count(stat_value) > 0
1
# Drop index should cause stats drop.
# Drop index should cause stats drop, but will not.
drop index SECOND on t2;
select sleep(3);
sleep(3)
0
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t2%' and index_name = 'SECOND' and stat_name in ('n_page_split');
count(stat_value) > 0
1
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t2%' and index_name = 'SECOND' and stat_name in ('n_pages_freed');
count(stat_value) > 0
1
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t2%' and index_name = 'SECOND' and stat_name in ('n_leaf_pages_defrag');
count(stat_value) > 0
1
Server Restarted
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_page_split');
count(stat_value) = 0
1
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_pages_freed');
count(stat_value) = 0
1
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_leaf_pages_defrag');
count(stat_value) = 0
1
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t2%' and stat_name in ('n_page_split');
count(stat_value) > 0
1
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t2%' and stat_name in ('n_pages_freed');
count(stat_value) > 0
1
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t2%' and stat_name in ('n_leaf_pages_defrag');
count(stat_value) > 0
1
SELECT stat_name, stat_value>0 FROM mysql.innodb_index_stats
WHERE table_name like '%t2%' AND index_name='SECOND';
stat_name stat_value>0
n_leaf_pages_defrag 1
n_leaf_pages_reserved 1
n_page_split 1
n_pages_freed 1
#
# MDEV-26636: Statistics must not be written for temporary tables
#
SET GLOBAL innodb_defragment_stats_accuracy = 1;
CREATE TEMPORARY TABLE t (a INT PRIMARY KEY, c CHAR(255) NOT NULL)
ENGINE=InnoDB;
INSERT INTO t SELECT seq, '' FROM seq_1_to_100;
SELECT * FROM mysql.innodb_index_stats where table_name like '%t1%';
database_name table_name index_name last_update stat_name stat_value sample_size stat_description
SELECT table_name, index_name, stat_name, stat_value>0
FROM mysql.innodb_index_stats;
table_name index_name stat_name stat_value>0
t2 PRIMARY n_leaf_pages_defrag 1
t2 PRIMARY n_leaf_pages_reserved 1
t2 PRIMARY n_page_split 1
t2 PRIMARY n_pages_freed 1
t2 SECOND n_leaf_pages_defrag 1
t2 SECOND n_leaf_pages_reserved 1
t2 SECOND n_page_split 1
t2 SECOND n_pages_freed 1
# Clean up
DROP TABLE t2;
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t2%' and stat_name in ('n_page_split');
count(stat_value) = 0
1
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t2%' and stat_name in ('n_pages_freed');
count(stat_value) = 0
1
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t2%' and stat_name in ('n_leaf_pages_defrag');
count(stat_value) = 0
1
SELECT * FROM mysql.innodb_index_stats;
database_name table_name index_name last_update stat_name stat_value sample_size stat_description
72 changes: 24 additions & 48 deletions mysql-test/suite/innodb/t/innodb_defrag_stats.test
View file
Original file line number Diff line number Diff line change
@@ -1,66 +1,45 @@
--source include/have_innodb.inc
--source include/big_test.inc
--source include/not_valgrind.inc
--source include/not_embedded.inc
--source include/have_sequence.inc

--disable_warnings
DROP TABLE if exists t1;
--enable_warnings
SET GLOBAL innodb_defragment_stats_accuracy = 20;

--disable_query_log
let $innodb_defragment_stats_accuracy_orig=`select @@innodb_defragment_stats_accuracy`;
--enable_query_log

select @@global.innodb_stats_persistent;
set global innodb_defragment_stats_accuracy = 20;
DELETE FROM mysql.innodb_index_stats;

--echo # Create table.
CREATE TABLE t1 (a INT NOT NULL PRIMARY KEY AUTO_INCREMENT, b VARCHAR(256), KEY SECOND(a, b)) ENGINE=INNODB;

--echo # Populate data
INSERT INTO t1 VALUES(1, REPEAT('A', 256));
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 SELECT seq, REPEAT('A', 256) FROM seq_1_to_1024;

--echo # Not enough page splits to trigger persistent stats write yet.
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_page_split');
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_pages_freed');
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_leaf_pages_defrag');

INSERT INTO t1 (b) SELECT b from t1;
INSERT INTO t1 SELECT seq, REPEAT('A', 256) FROM seq_1025_to_2048;

--echo # Persistent stats recorded.
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_page_split');
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_pages_freed');
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_leaf_pages_defrag');

--echo # Delete some rows.
BEGIN;
let $num_delete = 20;
while ($num_delete)
{
let $j = 100 * $num_delete;
eval delete from t1 where a between $j and $j + 30;
dec $num_delete;
}
COMMIT;

--source include/restart_mysqld.inc
--echo # Server Restarted

--echo # Confirm persistent stats still there after restart.
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_page_split');
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_pages_freed');
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_leaf_pages_defrag');

optimize table t1;
select sleep(2);

select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_page_split');
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_pages_freed');
Expand All @@ -84,7 +63,6 @@ select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like

--echo # Table rename should cause stats rename.
rename table t1 to t2;
select sleep(1);

select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_page_split');
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_pages_freed');
Expand All @@ -94,32 +72,30 @@ select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t2%' and stat_name in ('n_pages_freed');
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t2%' and stat_name in ('n_leaf_pages_defrag');

--echo # Drop index should cause stats drop.
--echo # Drop index should cause stats drop, but will not.
drop index SECOND on t2;
select sleep(3);

select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t2%' and index_name = 'SECOND' and stat_name in ('n_page_split');
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t2%' and index_name = 'SECOND' and stat_name in ('n_pages_freed');
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t2%' and index_name = 'SECOND' and stat_name in ('n_leaf_pages_defrag');
--sorted_result
SELECT stat_name, stat_value>0 FROM mysql.innodb_index_stats
WHERE table_name like '%t2%' AND index_name='SECOND';

--echo #
--echo # MDEV-26636: Statistics must not be written for temporary tables
--echo #
SET GLOBAL innodb_defragment_stats_accuracy = 1;
CREATE TEMPORARY TABLE t (a INT PRIMARY KEY, c CHAR(255) NOT NULL)
ENGINE=InnoDB;
INSERT INTO t SELECT seq, '' FROM seq_1_to_100;

--source include/restart_mysqld.inc
--echo Server Restarted

select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_page_split');
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_pages_freed');
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t1%' and stat_name in ('n_leaf_pages_defrag');
SELECT * FROM mysql.innodb_index_stats where table_name like '%t1%';

select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t2%' and stat_name in ('n_page_split');
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t2%' and stat_name in ('n_pages_freed');
select count(stat_value) > 0 from mysql.innodb_index_stats where table_name like '%t2%' and stat_name in ('n_leaf_pages_defrag');
--sorted_result
SELECT table_name, index_name, stat_name, stat_value>0
FROM mysql.innodb_index_stats;

--echo # Clean up
DROP TABLE t2;

select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t2%' and stat_name in ('n_page_split');
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t2%' and stat_name in ('n_pages_freed');
select count(stat_value) = 0 from mysql.innodb_index_stats where table_name like '%t2%' and stat_name in ('n_leaf_pages_defrag');

--disable_query_log
EVAL SET GLOBAL innodb_defragment_stats_accuracy = $innodb_defragment_stats_accuracy_orig;
--enable_query_log
SELECT * FROM mysql.innodb_index_stats;
3 changes: 2 additions & 1 deletion storage/innobase/btr/btr0defragment.cc
View file
Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
/*****************************************************************************
Copyright (C) 2012, 2014 Facebook, Inc. All Rights Reserved.
Copyright (C) 2014, 2019, MariaDB Corporation.
Copyright (C) 2014, 2021, 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
Expand Down Expand Up @@ -312,6 +312,7 @@ btr_defragment_save_defrag_stats_if_needed(
{
if (srv_defragment_stats_accuracy != 0 // stats tracking disabled
&& dict_index_get_space(index) != 0 // do not track system tables
&& !index->table->is_temporary()
&& index->stat_defrag_modified_counter
>= srv_defragment_stats_accuracy) {
dict_stats_defrag_pool_add(index);
Expand Down

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