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Commit 4a490d1a authored by Sergei Petrunia's avatar Sergei Petrunia
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MDEV-6111: Optimizer Trace: add tracing for semi-join optimizations 

Added:
- "semijoin_strategy_choice" element (actions in advance_sj_state(), name
  matches the name in MySQL)

- semijoin_table_pullout element.
parent 9fce9428
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Showing with 365 additions and 27 deletions
mysql-test/main/opt_trace.result
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mysql-test/main/opt_trace.test
View file @ 4a490d1a
......@@ -549,4 +549,22 @@ select JSON_DETAILED(JSON_EXTRACT(trace, '$**.analyzing_range_alternatives')) fr
DROP TABLE t1;
--echo #
--echo # Test for Semi-Join table pullout element
--echo #
create table t1 (a int primary key, b int);
insert into t1 (a) values (1),(2),(3),(4),(5);
create table t2 (a int primary key, b int);
insert into t2 (a) values (1),(2),(3),(4),(5);
create table t3 (a int);
insert into t3 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
explain
select * from t3 where (a,a) in (select t1.a, t2.a from t1, t2 where t1.b=t2.b);
select JSON_DETAILED(JSON_EXTRACT(trace, '$**.semijoin_table_pullout')) from INFORMATION_SCHEMA.OPTIMIZER_TRACE;
drop table t1,t2,t3;
set optimizer_trace='enabled=off';
sql/opt_subselect.cc
View file @ 4a490d1a
......@@ -2192,12 +2192,15 @@ int pull_out_semijoin_tables(JOIN *join)
TABLE_LIST *sj_nest;
DBUG_ENTER("pull_out_semijoin_tables");
List_iterator<TABLE_LIST> sj_list_it(join->select_lex->sj_nests);
/* Try pulling out of the each of the semi-joins */
while ((sj_nest= sj_list_it++))
{
List_iterator<TABLE_LIST> child_li(sj_nest->nested_join->join_list);
TABLE_LIST *tbl;
Json_writer_object trace_wrapper(join->thd);
Json_writer_object trace(join->thd, "semijoin_table_pullout");
Json_writer_array trace_arr(join->thd, "pulled_out_tables");
/*
Don't do table pull-out for nested joins (if we get nested joins here, it
......@@ -2296,7 +2299,8 @@ int pull_out_semijoin_tables(JOIN *join)
pulled_a_table= TRUE;
pulled_tables |= tbl->table->map;
DBUG_PRINT("info", ("Table %s pulled out (reason: func dep)",
tbl->table->alias.c_ptr()));
tbl->table->alias.c_ptr_safe()));
trace_arr.add(tbl->table->alias.c_ptr_safe());
/*
Pulling a table out of uncorrelated subquery in general makes
makes it correlated. See the NOTE to this funtion.
......@@ -2778,27 +2782,30 @@ void advance_sj_state(JOIN *join, table_map remaining_tables, uint idx,
{
POSITION *pos= join->positions + idx;
const JOIN_TAB *new_join_tab= pos->table;
Semi_join_strategy_picker *pickers[]=
{
&pos->firstmatch_picker,
&pos->loosescan_picker,
&pos->sjmat_picker,
&pos->dups_weedout_picker,
NULL,
};
if (join->emb_sjm_nest)
if (join->emb_sjm_nest || //(1)
!join->select_lex->have_merged_subqueries) //(2)
{
/*
We're performing optimization inside SJ-Materialization nest:
(1): We're performing optimization inside SJ-Materialization nest:
- there are no other semi-joins inside semi-join nests
- attempts to build semi-join strategies here will confuse
the optimizer, so bail out.
(2): Don't waste time on semi-join optimizations if we don't have any
semi-joins
*/
pos->sj_strategy= SJ_OPT_NONE;
return;
}
Semi_join_strategy_picker *pickers[]=
{
&pos->firstmatch_picker,
&pos->loosescan_picker,
&pos->sjmat_picker,
&pos->dups_weedout_picker,
NULL,
};
Json_writer_array trace_steps(join->thd, "semijoin_strategy_choice");
/*
Update join->cur_sj_inner_tables (Used by FirstMatch in this function and
LooseScan detector in best_access_path)
......@@ -2897,6 +2904,7 @@ void advance_sj_state(JOIN *join, table_map remaining_tables, uint idx,
*current_read_time= read_time;
*current_record_count= rec_count;
dups_producing_tables &= ~handled_fanout;
//TODO: update bitmap of semi-joins that were handled together with
// others.
if (is_multiple_semi_joins(join, join->positions, idx,
......@@ -2924,6 +2932,30 @@ void advance_sj_state(JOIN *join, table_map remaining_tables, uint idx,
}
}
}
if (unlikely(join->thd->trace_started() && pos->sj_strategy != SJ_OPT_NONE))
{
Json_writer_object tr(join->thd);
const char *sname;
switch (pos->sj_strategy) {
case SJ_OPT_MATERIALIZE:
sname= "SJ-Materialize";
break;
case SJ_OPT_MATERIALIZE_SCAN:
sname= "SJ-Materialize-Scan";
break;
case SJ_OPT_FIRST_MATCH:
sname= "FirstMatch";
break;
case SJ_OPT_DUPS_WEEDOUT:
sname= "DuplicateWeedout";
break;
default:
DBUG_ASSERT(0);
sname="Invalid";
}
tr.add("chosen_strategy", sname);
}
}
if ((emb_sj_nest= new_join_tab->emb_sj_nest))
......@@ -3000,6 +3032,8 @@ bool Sj_materialization_picker::check_qep(JOIN *join,
}
else
{
Json_writer_object trace(join->thd);
trace.add("strategy", "SJ-Materialization");
/* This is SJ-Materialization with lookups */
Cost_estimate prefix_cost;
signed int first_tab= (int)idx - mat_info->tables;
......@@ -3032,6 +3066,11 @@ bool Sj_materialization_picker::check_qep(JOIN *join,
*record_count= prefix_rec_count;
*handled_fanout= new_join_tab->emb_sj_nest->sj_inner_tables;
*strategy= SJ_OPT_MATERIALIZE;
if (unlikely(join->thd->trace_started()))
{
trace.add("records", *record_count);
trace.add("read_time", *read_time);
}
return TRUE;
}
}
......@@ -3040,6 +3079,8 @@ bool Sj_materialization_picker::check_qep(JOIN *join,
if (sjm_scan_need_tables && /* Have SJM-Scan prefix */
!(sjm_scan_need_tables & remaining_tables))
{
Json_writer_object trace(join->thd);
trace.add("strategy", "SJ-Materialization-Scan");
TABLE_LIST *mat_nest=
join->positions[sjm_scan_last_inner].table->emb_sj_nest;
SJ_MATERIALIZATION_INFO *mat_info= mat_nest->sj_mat_info;
......@@ -3088,6 +3129,11 @@ bool Sj_materialization_picker::check_qep(JOIN *join,
*read_time= prefix_cost;
*record_count= prefix_rec_count;
*handled_fanout= mat_nest->sj_inner_tables;
if (unlikely(join->thd->trace_started()))
{
trace.add("records", *record_count);
trace.add("read_time", *read_time);
}
return TRUE;
}
return FALSE;
......@@ -3151,6 +3197,8 @@ bool LooseScan_picker::check_qep(JOIN *join,
!(remaining_tables & loosescan_need_tables) &&
(new_join_tab->table->map & loosescan_need_tables))
{
Json_writer_object trace(join->thd);
trace.add("strategy", "SJ-Materialization-Scan");
/*
Ok we have LooseScan plan and also have all LooseScan sj-nest's
inner tables and outer correlated tables into the prefix.
......@@ -3181,6 +3229,11 @@ bool LooseScan_picker::check_qep(JOIN *join,
*/
*strategy= SJ_OPT_LOOSE_SCAN;
*handled_fanout= first->table->emb_sj_nest->sj_inner_tables;
if (unlikely(join->thd->trace_started()))
{
trace.add("records", *record_count);
trace.add("read_time", *read_time);
}
return TRUE;
}
return FALSE;
......@@ -3260,6 +3313,8 @@ bool Firstmatch_picker::check_qep(JOIN *join,
if (in_firstmatch_prefix() &&
!(firstmatch_need_tables & remaining_tables))
{
Json_writer_object trace(join->thd);
trace.add("strategy", "FirstMatch");
/*
Got a complete FirstMatch range. Calculate correct costs and fanout
*/
......@@ -3292,6 +3347,11 @@ bool Firstmatch_picker::check_qep(JOIN *join,
*handled_fanout= firstmatch_need_tables;
/* *record_count and *read_time were set by the above call */
*strategy= SJ_OPT_FIRST_MATCH;
if (unlikely(join->thd->trace_started()))
{
trace.add("records", *record_count);
trace.add("read_time", *read_time);
}
return TRUE;
}
}
......@@ -3370,6 +3430,8 @@ bool Duplicate_weedout_picker::check_qep(JOIN *join,
double sj_inner_fanout= 1.0;
double sj_outer_fanout= 1.0;
uint temptable_rec_size;
Json_writer_object trace(join->thd);
trace.add("strategy", "DuplicateWeedout");
if (first_tab == join->const_tables)
{
prefix_rec_count= 1.0;
......@@ -3430,6 +3492,11 @@ bool Duplicate_weedout_picker::check_qep(JOIN *join,
*record_count= prefix_rec_count * sj_outer_fanout;
*handled_fanout= dups_removed_fanout;
*strategy= SJ_OPT_DUPS_WEEDOUT;
if (unlikely(join->thd->trace_started()))
{
trace.add("records", *record_count);
trace.add("read_time", *read_time);
}
return TRUE;
}
return FALSE;
......@@ -3660,7 +3727,7 @@ void fix_semijoin_strategies_for_picked_join_order(JOIN *join)
join->best_positions[first].n_sj_tables= sjm->tables;
join->best_positions[first].sj_strategy= SJ_OPT_MATERIALIZE;
Json_writer_object semijoin_strategy(thd);
semijoin_strategy.add("semi_join_strategy","sj_materialize");
semijoin_strategy.add("semi_join_strategy","SJ-Materialization");
Json_writer_array semijoin_plan(thd, "join_order");
for (uint i= first; i < first+ sjm->tables; i++)
{
......@@ -3709,7 +3776,7 @@ void fix_semijoin_strategies_for_picked_join_order(JOIN *join)
POSITION dummy;
join->cur_sj_inner_tables= 0;
Json_writer_object semijoin_strategy(thd);
semijoin_strategy.add("semi_join_strategy","sj_materialize_scan");
semijoin_strategy.add("semi_join_strategy","SJ-Materialization-Scan");
Json_writer_array semijoin_plan(thd, "join_order");
for (i= first + sjm->tables; i <= tablenr; i++)
{
......@@ -3747,7 +3814,7 @@ void fix_semijoin_strategies_for_picked_join_order(JOIN *join)
*/
join->cur_sj_inner_tables= 0;
Json_writer_object semijoin_strategy(thd);
semijoin_strategy.add("semi_join_strategy","firstmatch");
semijoin_strategy.add("semi_join_strategy","FirstMatch");
Json_writer_array semijoin_plan(thd, "join_order");
for (idx= first; idx <= tablenr; idx++)
{
......@@ -3785,7 +3852,7 @@ void fix_semijoin_strategies_for_picked_join_order(JOIN *join)
*/
join->cur_sj_inner_tables= 0;
Json_writer_object semijoin_strategy(thd);
semijoin_strategy.add("semi_join_strategy","sj_materialize");
semijoin_strategy.add("semi_join_strategy","LooseScan");
Json_writer_array semijoin_plan(thd, "join_order");
for (idx= first; idx <= tablenr; idx++)
{
......
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