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MDEV-34888 Implement SEMIJOIN() and SUBQUERY() hints

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This commit is contained in:
Oleg Smirnov
2024-09-11 19:53:57 +07:00
parent e3bf4c826c
commit 2c8f6058c1
28 changed files with 3712 additions and 164 deletions
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59
sql/opt_subselect.cc
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@@ -466,6 +466,7 @@ enum_nested_loop_state
end_sj_materialize(JOIN *join, JOIN_TAB *join_tab, bool end_of_records);
/*
Check if Materialization strategy is allowed for given subquery predicate.
@@ -485,7 +486,7 @@ bool is_materialization_applicable(THD *thd, Item_in_subselect *in_subs,
/*
Check if the subquery predicate can be executed via materialization.
The required conditions are:
0. The materialization optimizer switch was set.
0. The materialization optimizer switch/hint was set.
1. Subquery is a single SELECT (not a UNION).
TODO: this is a limitation that can be fixed
2. Subquery is not a table-less query. In this case there is no
@@ -514,7 +515,8 @@ bool is_materialization_applicable(THD *thd, Item_in_subselect *in_subs,
select_lex->sj_subselects list to be populated for every EXECUTE.
*/
if (optimizer_flag(thd, OPTIMIZER_SWITCH_MATERIALIZATION) && // 0
uint strategies_allowed= child_select->subquery_strategies_allowed(thd);
if ((strategies_allowed & SUBS_MATERIALIZATION) && // 0
!child_select->is_part_of_union() && // 1
parent_unit->first_select()->leaf_tables.elements && // 2
child_select->outer_select() &&
@@ -740,7 +742,7 @@ int check_and_do_in_subquery_rewrites(JOIN *join)
yet. They are checked later in convert_join_subqueries_to_semijoins(),
look for calls to block_conversion_to_sj().
*/
if (optimizer_flag(thd, OPTIMIZER_SWITCH_SEMIJOIN) &&
if (select_lex->semijoin_enabled(thd) &&
in_subs && // 1
!select_lex->is_part_of_union() && // 2
!select_lex->group_list.elements && !join->order && // 3
@@ -816,7 +818,7 @@ int check_and_do_in_subquery_rewrites(JOIN *join)
with jtbm strategy
*/
if (in_subs->emb_on_expr_nest == NO_JOIN_NEST &&
optimizer_flag(thd, OPTIMIZER_SWITCH_SEMIJOIN))
select_lex->semijoin_enabled(thd))
{
in_subs->is_flattenable_semijoin= FALSE;
if (!in_subs->is_registered_semijoin)
@@ -834,11 +836,11 @@ int check_and_do_in_subquery_rewrites(JOIN *join)
/*
IN-TO-EXISTS is the only universal strategy. Choose it if the user
allowed it via an optimizer switch, or if materialization is not
allowed it via an optimizer switch/hint, or if materialization is not
possible.
*/
if (optimizer_flag(thd, OPTIMIZER_SWITCH_IN_TO_EXISTS) ||
!in_subs->has_strategy())
uint strategies_allowed= select_lex->subquery_strategies_allowed(thd);
if (strategies_allowed & SUBS_IN_TO_EXISTS || !in_subs->has_strategy())
in_subs->add_strategy(SUBS_IN_TO_EXISTS);
}
@@ -2559,11 +2561,11 @@ bool optimize_semijoin_nests(JOIN *join, table_map all_table_map)
sj_nest->sj_mat_info= NULL;
/*
The statement may have been executed with 'semijoin=on' earlier.
We need to verify that 'semijoin=on' still holds.
The statement may have been executed as a semijoin earlier.
We need to verify that semijoin materialization is still allowed.
*/
if (optimizer_flag(join->thd, OPTIMIZER_SWITCH_SEMIJOIN) &&
optimizer_flag(join->thd, OPTIMIZER_SWITCH_MATERIALIZATION))
if (sj_nest->nested_join->sj_enabled_strategies &
OPTIMIZER_SWITCH_MATERIALIZATION)
{
if ((sj_nest->sj_inner_tables & ~join->const_table_map) && /* not everything was pulled out */
!sj_nest->sj_subq_pred->is_correlated &&
@@ -3050,10 +3052,20 @@ void optimize_semi_joins(JOIN *join, table_map remaining_tables, uint idx,
(dusp_producing_tables & handled_fanout is true), then
*current_read_time is updated and the cost for the next
strategy can be smaller than *current_read_time.
The strategy may be disabled by an optimizer switch or a hint,
which is checked at (1). Currently, this is applicable only to
Duplicate Weedout since other disabled strategies will will be
cut off earlier and will not make it here. However, since
Duplicate Weedout serves as the default fallback strategy, it is
chosen even when disabled, provided no other viable alternatives
are available.
*/
if ((dups_producing_tables & handled_fanout) ||
if (((dups_producing_tables & handled_fanout) ||
(read_time + COST_EPS < *current_read_time &&
!(handled_fanout & pos->inner_tables_handled_with_other_sjs)))
!(handled_fanout & pos->inner_tables_handled_with_other_sjs))) &&
(!(*strategy)->is_disabled() ||
pos->sj_strategy == SJ_OPT_NONE)) // (1)
{
DBUG_ASSERT(pos->sj_strategy != sj_strategy);
/*
@@ -3481,7 +3493,8 @@ bool Firstmatch_picker::check_qep(JOIN *join,
POSITION *loose_scan_pos)
{
if (new_join_tab->emb_sj_nest &&
optimizer_flag(join->thd, OPTIMIZER_SWITCH_FIRSTMATCH) &&
(new_join_tab->emb_sj_nest->nested_join->sj_enabled_strategies &
OPTIMIZER_SWITCH_FIRSTMATCH) &&
!join->outer_join)
{
const table_map outer_corr_tables=
@@ -3725,10 +3738,22 @@ bool Duplicate_weedout_picker::check_qep(JOIN *join,
POSITION *p= join->positions + j;
dups_cost= COST_ADD(dups_cost, p->read_time);
if (p->table->emb_sj_nest)
TABLE_LIST *emb_sj_nest= p->table->emb_sj_nest;
if (emb_sj_nest)
{
sj_inner_fanout= COST_MULT(sj_inner_fanout, p->records_out);
dups_removed_fanout |= p->table->table->map;
/*
Duplicate Weedout is the default fallback strategy. It is used when
all other strategies are disabled by either an optimizer switch or
a hint. So, mark it as disabled for when there are other enabled
strategies to choose from
*/
disabled |=
emb_sj_nest->nested_join->sj_enabled_strategies != 0 && // (1)
!(emb_sj_nest->nested_join->sj_enabled_strategies &
OPTIMIZER_SWITCH_DUPSWEEDOUT);
}
else
{
@@ -3936,7 +3961,9 @@ at_sjmat_pos(const JOIN *join, table_map remaining_tables, const JOIN_TAB *tab,
TABLE_LIST *emb_sj_nest= tab->emb_sj_nest;
table_map suffix= remaining_tables & ~tab->table->map;
if (emb_sj_nest && emb_sj_nest->sj_mat_info &&
!(suffix & emb_sj_nest->sj_inner_tables))
!(suffix & emb_sj_nest->sj_inner_tables) &&
(emb_sj_nest->nested_join->sj_enabled_strategies &
OPTIMIZER_SWITCH_MATERIALIZATION))
{
/*
Walk back and check if all immediately preceding tables are from