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

Browse Source 
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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6
sql/sql_parse.cc
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@ -5592,7 +5592,7 @@ static bool execute_sqlcom_select(THD *thd, TABLE_LIST *all_tables)
bool res;
/* assign global limit variable if limit is not given */
{
SELECT_LEX *param= lex->unit.global_parameters;
SELECT_LEX *param= lex->unit.global_parameters();
if (!param->explicit_limit)
param->select_limit=
new Item_int((ulonglong) thd->variables.select_limit);
@ -6675,7 +6675,6 @@ mysql_new_select(LEX *lex, bool move_down)
unit->first_select()->context.outer_context;
}
select_lex->master_unit()->global_parameters= select_lex;
select_lex->include_global((st_select_lex_node**)&lex->all_selects_list);
lex->current_select= select_lex;
/*
@ -7642,7 +7641,7 @@ bool st_select_lex_unit::add_fake_select_lex(THD *thd_arg)
fake_select_lex->context.outer_context=first_sl->context.outer_context;
/* allow item list resolving in fake select for ORDER BY */
fake_select_lex->context.resolve_in_select_list= TRUE;
fake_select_lex->context.select_lex= fake_select_lex;
fake_select_lex->context.select_lex= fake_select_lex;
if (!is_union())
{
@ -7652,7 +7651,6 @@ bool st_select_lex_unit::add_fake_select_lex(THD *thd_arg)
(SELECT ... LIMIT n) ORDER BY order_list [LIMIT m]
just before the parser starts processing order_list
*/
global_parameters= fake_select_lex;
fake_select_lex->no_table_names_allowed= 1;
thd_arg->lex->current_select= fake_select_lex;
}