> ------------------------------------------------------------
> revno: 3324
> revision-id: joro@sun.com-20091223151122-ada73up1yydh0emt
> parent: joro@sun.com-20100119124841-38vva51cuq3if7dc
> committer: Georgi Kodinov <joro@sun.com>
> branch nick: B49512-5.1-bugteam
> timestamp: Wed 2009-12-23 17:11:22 +0200
> message:
>   Bug #49512 : subquery with aggregate function crash
>     subselect_single_select_engine::exec()
>   
>   When a subquery doesn't need to be evaluated because
>   it returns only aggregate functions and these aggregates
>   can be calculated from the metadata about the table it
>   was not updating all the relevant members of the JOIN 
>   structure to reflect that this is a constant query.
>   This caused problems to the enclosing subquery 
>   ('<> SOME' in the test case above) trying to read some
>   data about the tables.
>   
>   Fixed by setting const_tables to the number of tables 
>   when the SELECT is optimized away.