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Bug #55656: mysqldump can be slower after bug 39653 fix.

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After fix for bug 39653 the shortest available secondary index was used for
full table scan. Primary clustered key was used only if no secondary index
can be used. However, when chosen secondary index includes all fields of the
table being scanned it's better to use primary index since the amount of
data to scan is the same but the primary index is clustered.
Now the find_shortest_key function takes this into account.
This commit is contained in:
Evgeny Potemkin
2010-08-26 13:31:04 +04:00
parent 79aefacb04
commit 151af144ff
3 changed files with 125 additions and 18 deletions
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25
mysql-test/suite/innodb/t/innodb_mysql.test
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@ -781,5 +781,30 @@ disconnect con2;
DROP TABLE t1,t2;
--echo #
--echo # Bug#55656: mysqldump can be slower after bug #39653 fix
--echo #
CREATE TABLE t1 (a INT , b INT, c INT, d INT,
KEY (b), PRIMARY KEY (a,b)) ENGINE=INNODB;
INSERT INTO t1 VALUES (1,1,1,1), (2,2,2,2), (3,3,3,3);
--query_vertical EXPLAIN SELECT COUNT(*) FROM t1
DROP INDEX b ON t1;
CREATE INDEX b ON t1(a,b);
--query_vertical EXPLAIN SELECT COUNT(*) FROM t1
DROP INDEX b ON t1;
CREATE INDEX b ON t1(a,b,c);
--query_vertical EXPLAIN SELECT COUNT(*) FROM t1
DROP INDEX b ON t1;
CREATE INDEX b ON t1(a,b,c,d);
--query_vertical EXPLAIN SELECT COUNT(*) FROM t1
DROP TABLE t1;
--echo #
--echo End of 5.1 tests