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MDEV-8989: ORDER BY optimizer ignores equality propagation

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Post-fix: add comments, remove dead-code.
This commit is contained in:
Sergei Petrunia
2016-05-27 15:16:08 +03:00
parent 99cd5a962c
commit a85f6533f1
1 changed files with 13 additions and 17 deletions
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30
sql/sql_select.cc
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@ -12342,30 +12342,26 @@ remove_const(JOIN *join,ORDER *first_order, COND *cond,
Item *item= order->item[0]; Item *item= order->item[0];
/* /*
We are using Context_identity below. This means only do TODO: equality substitution in the context of ORDER BY is
substitution when equality means sometimes allowed when it is not allowed in the general case.
We make the below call for its side effect: it will locate the
multiple equality the item belongs to and set item->item_equal
accordingly.
*/ */
Item *res= item->propagate_equal_fields(join->thd, Item *res= item->propagate_equal_fields(join->thd,
Value_source:: Value_source::
Context_identity(), Context_identity(),
join->cond_equal); join->cond_equal);
if (res != item) Item_equal *item_eq;
if ((item_eq= res->get_item_equal()))
{ {
/* Substituted to a constant */ Item *first= item_eq->get_first(NO_PARTICULAR_TAB, NULL);
can_subst_to_first_table= true; if (first->const_item() || first->used_tables() ==
} first_table_bit)
else
{
Item_equal *item_eq= item->get_item_equal();
if (item_eq)
{ {
Item *first= item_eq->get_first(NO_PARTICULAR_TAB, NULL); can_subst_to_first_table= true;
if (first->const_item() || first->used_tables() ==
first_table_bit)
{
can_subst_to_first_table= true;
}
} }
} }
} }