Re: [Maria-developers] Please review: [Commits] Rev 3199: Fix bug lp:858148. in file:///home/tsk/mprog/src/5.3/

OK to push. Regards, Igor. On 09/28/2011 07:23 AM, Timour Katchaounov wrote:

Hi Igor,

Could you please review the following fix. It is very much related to a bug you fixed: https://bugs.launchpad.net/bugs/702301

Thanks, Timour

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At file:///home/tsk/mprog/src/5.3/

------------------------------------------------------------ revno: 3199 revision-id: timour@askmonty.org-20110928142043-b88ob3qytbroxdks parent: psergey@askmonty.org-20110928090147-izz3ebqbcrnakndu fixes bug(s): https://launchpad.net/bugs/858148 committer: timour@askmonty.org branch nick: 5.3 timestamp: Wed 2011-09-28 17:20:43 +0300 message: Fix bug lp:858148.

Analysis: The crash is a result of the same cause as all similar bugs (lp:827416, lp:718763, lp:778413, lp:806943, lp:611690). The general pattern is that some optimization requires the evaluation of some condition (e.g. the WHERE clause), and this condition contains a subquery, such that the subquery itself requires a temporary table for its execution. During the subquery execution the original tables in the FROM clause are replaced by the temporary table needed for the final GROUP or ORDER operation. All this happens during optimization of the outer query. Later when EXPLAIN is run for the subquery, explain attempts to print the name of the tables in the FROM clause, but it finds there a temporary table without a corresponding TABLE_LIST object. The attempt to print the name of a NULL table list results in a crash.

Solution: This patch extends the fix to bug lp:702301, and dissalows constant substitution of aggregate functions if the filter condition used to check MIN/MAX keys is an expensive condition.