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MDEV-334: Backport of UNION ALL optimization from mysql-5.7.

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Although the original code of mysql-5.7 was adjusted
to the current MariaDB code the main ideas of the optimization
were preserved.
This commit is contained in:
Igor Babaev
2014-10-14 09:36:50 -07:00
parent fec5ab5a56
commit 3c4bb0e872
31 changed files with 853 additions and 327 deletions
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2
sql/sql_select.h
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@ -1413,7 +1413,7 @@ public:
having_value != Item::COND_FALSE);
}
bool empty_result() { return (zero_result_cause && !implicit_grouping); }
bool change_result(select_result *result);
bool change_result(select_result *new_result, select_result *old_result);
bool is_top_level_join() const
{
return (unit == &thd->lex->unit && (unit->fake_select_lex == 0 ||