> ------------------------------------------------------------
> revno: 3351.41.1
> revision-id: alexey.kopytov@sun.com-20100430111048-jdls6ofn4kkmpt09
> parent: sergey.glukhov@sun.com-20100329134249-03wyhzp5k92dzhcb
> committer: Alexey Kopytov <Alexey.Kopytov@Sun.com>
> branch nick: my51-bug48419
> timestamp: Fri 2010-04-30 15:10:48 +0400
> message:
>   Bug #48419: another explain crash..
>   
>   WHERE predicates containing references to empty tables in a
>   subquery were handled incorrectly by the optimizer when
>   executing EXPLAIN. As a result, the optimizer could try to
>   evaluate such predicates rather than just stop with
>   "Impossible WHERE noticed after reading const tables" as 
>   it would do in a non-subquery case. This led to valgrind 
>   errors and crashes.
>   
>   Fixed the code checking the above condition so that subqueries
>   are not excluded and hence are handled in the same way as top
>   level SELECTs.