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MDEV-35443: opt_search_plan_for_table() may degrade to full table scan

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opt_calc_index_goodness(): Correct an inaccurate condition.
We can very well use a clustered index of a table that is subject
to online rebuild. But we must not choose an index that has not been
committed (it is a secondary index that was not fully created)
or that is corrupted or not a normal B-tree index.

opt_search_plan_for_table(): Remove some redundant code, now that
opt_calc_index_goodness() checks against corrupted indexes.

The test case allows this code to be exercised. The main observation
in the following:
	./mtr --rr innodb.stats_persistent
	rr replay var/log/mysqld.1.rr/latest-trace
should be that when opt_search_plan_for_table() is being invoked by
dict_stats_update_persistent() on the being-altered statistics table
in the 2nd call after ha_innobase::inplace_alter_table(),
and the fix in opt_calc_index_goodness() is absent,
it would choose the code path if (n_fields == 0), that is, a full
table scan, instead of searching for the record. The GDB commands to
execute in "rr replay" would be as follows:
	break ha_innobase::inplace_alter_table
	continue
	break opt_search_plan_for_table
	continue
	continue
	next
	next
	…

Reviewed by: Vladislav Lesin
This commit is contained in:
Marko Mäkelä
2024-12-19 14:05:16 +02:00
parent a226f12675
commit e5c4c0842d
4 changed files with 33 additions and 8 deletions
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11
mysql-test/suite/innodb/t/stats_persistent.test
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@ -14,14 +14,25 @@ SET DEBUG_SYNC='dict_stats_update_persistent SIGNAL stop WAIT_FOR go';
--connect(con1, localhost, root)
SET DEBUG_SYNC='now WAIT_FOR stop';
--connect(con2, localhost, root)
SET DEBUG_SYNC='innodb_inplace_alter_table_enter SIGNAL astop WAIT_FOR ago';
send ALTER TABLE mysql.innodb_index_stats FORCE;
--connection con1
--replace_column 1 SUM
SELECT SUM(DATA_LENGTH+INDEX_LENGTH) FROM information_schema.TABLES WHERE ENGINE='InnoDB';
SET DEBUG_SYNC='now WAIT_FOR astop';
SET DEBUG_SYNC='now SIGNAL go';
--disconnect con1
--connection default
--reap
SET DEBUG_SYNC='now SIGNAL ago';
--connection con2
reap;
--disconnect con2
--connection default
SET DEBUG_SYNC= 'RESET';
DROP TABLE t1;