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MDEV-17761: Odd optimizer choice with ORDER BY LIMIT and condition selectivity

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Make the "ORDER BY ... LIMIT n" optimizer take into account condition
selectivity data from EITS (not just from potential range accesses).
This commit is contained in:
Sergei Petrunia
2019-01-23 15:49:49 +03:00
parent 36a2a185fe
commit b7a784ae25
5 changed files with 145 additions and 0 deletions
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17
mysql-test/main/range_vs_index_merge.test
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@ -718,6 +718,23 @@ SELECT * FROM City
ORDER BY Population LIMIT 5;
SHOW STATUS LIKE 'Handler_read_%';
set @tmp_mdev585=@@optimizer_use_condition_selectivity;
set optimizer_use_condition_selectivity=1;
--replace_column 9 #
EXPLAIN
SELECT * FROM City
WHERE ((Name > 'Ca' AND Name < 'Cf') OR (Country > 'E' AND Country < 'H'))
AND (Population >= 100000 AND Population < 120000)
ORDER BY Population LIMIT 5;
FLUSH STATUS;
SELECT * FROM City
WHERE ((Name > 'Ca' AND Name < 'Cf') OR (Country > 'E' AND Country < 'H'))
AND (Population >= 100000 AND Population < 120000)
ORDER BY Population LIMIT 5;
SHOW STATUS LIKE 'Handler_read_%';
set optimizer_use_condition_selectivity=@tmp_mdev585;
set optimizer_switch='index_merge=off';