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Re: MySQL 5.5 Query Optimizer - Massive Regression (vs 5.0)
Posted by: Chris Ricks
Date: February 01, 2012 07:33PM

Some further investigation seems to indicate that only the first column in the index is used for query plan evaluation, for example:

* Supplying a query that constrains on both client_id and settlement AND providing an index hint to use IX_settlement_client results in 5606808 rows being examined according to EXPLAIN
* Supplying the same query without a query hint AND without a client_id constraint results in 5606808 rows being examined according to EXPLAIN

Has anyone else observed this?

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Re: MySQL 5.5 Query Optimizer - Massive Regression (vs 5.0)
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February 01, 2012 07:33PM


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