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Fixed the bug mdev-12788.

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In some rare cases queries with UNION ALL
using a derived table specified by
a grouping select with a subquery in WHERE and
impossible HAVING detected after constant row
substitution could hang.
The cause was not a proper return from the
function subselect_single_select_engine::exec()
in the case when the subquery was not optimized
beforehand and the optimization performed
in this function requested for a change of the
subquery engine. This was fixed.
Also a change was applied that avoided execution
of a subquery if impossible having was detected
for the main query at the optimization stage.
This commit is contained in:
Igor Babaev
2017-05-18 23:54:43 -07:00
parent 4807df6f20
commit 5e9d651108
4 changed files with 63 additions and 2 deletions
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6
sql/sql_select.cc
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@@ -1984,7 +1984,8 @@ JOIN::optimize_inner()
having= new (thd->mem_root) Item_int(thd, (longlong) 0,1);
zero_result_cause= "Impossible HAVING noticed after reading const tables";
error= 0;
DBUG_RETURN(0);
select_lex->mark_const_derived(zero_result_cause);
goto setup_subq_exit;
}
}
@@ -3377,7 +3378,8 @@ void JOIN::exec_inner()
condtions may be arbitrarily costly, and because the optimize phase
might not have produced a complete executable plan for EXPLAINs.
*/
if (exec_const_cond && !(select_options & SELECT_DESCRIBE) &&
if (!zero_result_cause &&
exec_const_cond && !(select_options & SELECT_DESCRIBE) &&
!exec_const_cond->val_int())
zero_result_cause= "Impossible WHERE noticed after reading const tables";