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Re: [Commits] Rev 3115: Fix bug lp:782305 in file:///home/tsk/mprog/src/5.3-work/



18.07.2011 23:45, timour@xxxxxxxxxxxx пишет:
At file:///home/tsk/mprog/src/5.3-work/

revno: 3115
revision-id: timour@xxxxxxxxxxxx-20110718204538-2976m25qh52g6l69
parent: igor@xxxxxxxxxxxx-20110717075207-sg6f40o1ps8mwxrj
fixes bug(s): https://launchpad.net/bugs/782305
committer: timour@xxxxxxxxxxxx
branch nick: 5.3-work
timestamp: Mon 2011-07-18 23:45:38 +0300
   Fix bug lp:782305

   Both the wrong result and the valgrind warning were a result
   of incomplete cleanup of the MIN/MAX subquery rewrite. At the
   first execution of the query, the non-aggregate subquery is
   transformed into an aggregate MIN/MAX subquery. During the
   fix_fields phase of the MIN/MAX function, it sets the property
   st_select_lex::with_sum_func to true.

   The second execution of the query finds this flag to be ON.
   When optimization reaches the same MIN/MAX subquery
   transformation, it tests if the subquery is an aggregate or not.
   Since select_lex->with_sum_func == true from the previous
   execution, the transformation executes the second branch that
   handles aggregate subqueries. This substitutes the subquery
   Item into a Item_maxmin_subselect. At the same time elsewhere
   it is assumed that the subquery Item is of type
   Item_allany_subselect. Ultimately this results in casting the
   actual object to the wrong class, and calling the wrong
   any_value() method from empty_underlying_subquery().

   Cleanup the st_select_lex::with_sum_func property in the case
   when the MIN/MAX transformation was performed for a non-aggregate
   subquery, so that the transformation can be repeated.

The patch is OK.

SUBS_MAXMIN_ENGINE is really good name, thank you!