[TYPO3-core] RFC #13273: Bug: Caching framework sub-select is slow because mysql does not use indexes on outer query

[Christian Kuhn]

Reminder #3

This is still an important performance fix for people using the caching 
framework. Patch is in production on our systems for month now.

Regards
Christian

Christian Kuhn wrote:
> Type: bugfix
> 
> BT reference: http://bugs.typo3.org/view.php?id=13273
> 
> Branches: trunk, TYPO3_4-3
> 
> Problem:
> mysql is unable to use indexes for outer query if where clause is a sub
> select [1]. This makes tag-deletion in the caching framework with db
> backend very slow on bigger tables because mysql happily decides to
> perform a full table scan.
> 
> Solution:
> Separate queries and do more logic with php.