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Re: Execution plan changes back and forth
Posted by: Rick James
Date: May 27, 2010 08:26PM

Quote

from (
select pe.attribute_value
from
That is a huge JOIN, but selects only one field? It it merely to make sure that the JOIN succeeds?

"IN ( SELECT ... )" is often more efficiently done via a JOIN.

InnoDB or MyISAM? (InnoDB is more prone to random EXPLAIN changes.)

What version are you running? Changing the setting of this may help:
http://dev.mysql.com/doc/refman/5.0/en/innodb-parameters.html#sysvar_innodb_use_legacy_cardinality_algorithm
http://dev.mysql.com/doc/refman/5.1/en/innodb-parameters.html#sysvar_innodb_use_legacy_cardinality_algorithm
The InnoDB "plugin" has more settings.

This table seems to be pivotal in issue: csm_user_group ug; SHOW CREATE TABLE and SHOW TABLE STATUS.

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Re: Execution plan changes back and forth
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