Details
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Bug
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Status: Closed (View Workflow)
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Blocker
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Resolution: Fixed
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10.0(EOL), 10.1(EOL), 10.2(EOL), 10.3(EOL), 10.4(EOL), 10.5
Description
The following test demonstrates that while InnoDB is collecting statistics are collected on a large table, any access from SQL to that table will be unnecessarily blocked by dict_table_stats_lock():
diff a/mysql-test/suite/innodb/t/stats_persistent.test b/mysql-test/suite/innodb/t/stats_persistent.test
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new file mode 100644
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--- /dev/null
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+++ b/mysql-test/suite/innodb/t/stats_persistent.test
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@@ -0,0 +1,26 @@
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+--source include/have_innodb.inc
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+--source include/have_debug.inc
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+--source include/have_debug_sync.inc
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+--source include/count_sessions.inc
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+
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+CREATE TABLE t1(a int) ENGINE=INNODB STATS_PERSISTENT=1;
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+
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+SET DEBUG_SYNC='dict_stats_update_persistent SIGNAL stop WAIT_FOR go';
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+send ANALYZE TABLE t1;
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+
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+--connect(con1, localhost, root)
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+SET DEBUG_SYNC='now WAIT_FOR stop';
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+
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+SELECT * FROM information_schema.TABLES WHERE ENGINE='InnoDB';
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+
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+SET DEBUG_SYNC='now SIGNAL go';
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+--disconnect con1
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+
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+--connection default
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+--reap
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+SET DEBUG_SYNC= 'RESET';
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+DROP TABLE t1;
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+
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+--source include/wait_until_count_sessions.inc
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diff a/storage/innobase/dict/dict0stats.cc b/storage/innobase/dict/dict0stats.cc
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--- a/storage/innobase/dict/dict0stats.cc
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+++ b/storage/innobase/dict/dict0stats.cc
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@@ -2207,6 +2207,8 @@ dict_stats_update_persistent(
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dict_table_stats_lock(table, RW_X_LATCH);
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+ DEBUG_SYNC_C("dict_stats_update_persistent");
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+
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/* analyze the clustered index first */
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index = dict_table_get_first_index(table); |
We can allow multiple threads to collect statistics for the same table in parallel, but only one thread at a time may be allowed to update the statistics. To prevent unnecessary work for multiple threads collecting statistics for the same table, we might introduce a counter of pending statistics-gathering operations. MySQL 5.7.32 preferred to introduce a lazily initialized mutex, which would not be easy to merge to 10.4.
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