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MDEV-5123 Remove duplicated conditions pushed both to join_tab->select_cond and join_tab->cache_select->cond for blocked joins.

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BNL and BNLH joins pre-filter the records from a joined table via JOIN_TAB::cache_select->cond.
There is no need to re-evaluate the same conditions via JOIN_TAB::select_cond. This patch removes
the duplicated conditions from the top-level conjuncts of each pushed condition.

The added "Using where" in few EXPLAINs is due to taking into account tab->cache_select->cond
in addition to tab->select_cond in JOIN::save_explain_data_intern.
This commit is contained in:
timour@askmonty.org 2013-10-18 11:45:25 +03:00
parent adbb439358
commit afed809297
12 changed files with 210 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

49
mysql-test/r/join_cache.result
View File

@ -5058,7 +5058,7 @@ EXPLAIN
SELECT * FROM t1,t2 WHERE t1.a < 3 and t2.a IS NULL;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range PRIMARY PRIMARY 4 NULL 3 Using where; Using index
1 SIMPLE t2 hash_range idx #hash#idx:idx 5:5 const 4 Using index condition; Rowid-ordered scan; Using join buffer (flat, BNLH join)
1 SIMPLE t2 hash_range idx #hash#idx:idx 5:5 const 4 Using index condition; Using where; Rowid-ordered scan; Using join buffer (flat, BNLH join)
SELECT * FROM t1,t2 WHERE t1.a < 3 and t2.a IS NULL;
a a b
1 NULL 10
@ -5637,4 +5637,51 @@ c
set join_buffer_size=default;
set optimizer_switch=@tmp_optimizer_switch;
DROP table t1,t2,t3;
#
# MDEV-5123 Remove duplicated conditions pushed both to join_tab->select_cond and join_tab->cache_select->cond for blocked joins.
#
set join_cache_level=default;
set expensive_subquery_limit=0;
create table t1 (c1 int);
create table t2 (c2 int);
create table t3 (c3 int);
insert into t1 values (1), (2);
insert into t2 values (1), (2);
insert into t3 values (2);
explain
select count(*) from t1 straight_join t2
where c1 = c2-0 and c2 <= (select max(c3) from t3 where c3 = 2 and @counter:=@counter+1);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2
1 PRIMARY t2 ALL NULL NULL NULL NULL 2 Using where; Using join buffer (flat, BNL join)
2 UNCACHEABLE SUBQUERY t3 system NULL NULL NULL NULL 1
set @counter=0;
select count(*) from t1 straight_join t2
where c1 = c2-0 and c2 <= (select max(c3) from t3 where c3 = 2 and @counter:=@counter+1);
count(*)
2
select @counter;
@counter
2
explain
select count(*) from t1 straight_join t2
where c1 = c2-0 and
c2 <= (select max(c3) from t3 where c3 = 2 and @counter:=@counter+1) and
c2 / 2 = 1;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2
1 PRIMARY t2 ALL NULL NULL NULL NULL 2 Using where; Using join buffer (flat, BNL join)
2 UNCACHEABLE SUBQUERY t3 system NULL NULL NULL NULL 1
set @counter=0;
select count(*) from t1 straight_join t2
where c1 = c2-0 and
c2 <= (select max(c3) from t3 where c3 = 2 and @counter:=@counter+1) and
c2 / 2 = 1;
count(*)
1
select @counter;
@counter
2
drop table t1,t2,t3;
set expensive_subquery_limit=default;
set @@optimizer_switch=@save_optimizer_switch;

14
mysql-test/r/limit_rows_examined.result
View File

@ -747,27 +747,27 @@ ERROR HY000: Sort aborted:
SHOW STATUS LIKE 'Handler_read%';
Variable_name Value
Handler_read_first 0
Handler_read_key 4
Handler_read_key 5
Handler_read_last 0
Handler_read_next 0
Handler_read_prev 0
Handler_read_rnd 0
Handler_read_rnd_deleted 0
Handler_read_rnd_next 52
Handler_read_rnd_next 46
SHOW STATUS LIKE 'Handler_tmp%';
Variable_name Value
Handler_tmp_update 0
Handler_tmp_write 66
Handler_tmp_write 70
FLUSH STATUS;
SELECT a AS field1, alias2.d AS field2, alias2.f AS field3, alias2.e AS field4, b AS field5
FROM t1, t2 AS alias2, t2 AS alias3
WHERE alias3.c IN ( SELECT 1 UNION SELECT 6 )
GROUP BY field1, field2, field3, field4, field5
LIMIT ROWS EXAMINED 250;
LIMIT ROWS EXAMINED 124;
field1 field2 field3 field4 field5
00:21:38 06:07:10 a 2007-06-08 04:35:26 2007-05-28 00:00:00
Warnings:
Warning 1931 Query execution was interrupted. The query examined at least 251 rows, which exceeds LIMIT ROWS EXAMINED (250). The query result may be incomplete.
Warning 1931 Query execution was interrupted. The query examined at least 125 rows, which exceeds LIMIT ROWS EXAMINED (124). The query result may be incomplete.
SHOW STATUS LIKE 'Handler_read%';
Variable_name Value
Handler_read_first 0
@ -777,11 +777,11 @@ Handler_read_next 0
Handler_read_prev 0
Handler_read_rnd 2
Handler_read_rnd_deleted 1
Handler_read_rnd_next 110
Handler_read_rnd_next 47
SHOW STATUS LIKE 'Handler_tmp%';
Variable_name Value
Handler_tmp_update 0
Handler_tmp_write 133
Handler_tmp_write 70
drop table t1, t2;
MDEV-161 LIMIT_ROWS EXAMINED: query with the limit and NOT EXISTS, without GROUP BY or aggregate,

12
mysql-test/r/range.result
View File

@ -221,27 +221,27 @@ update t1 set y=x;
explain select * from t1, t1 t2 where t1.y = 8 and t2.x between 7 and t1.y+0;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref y y 5 const 1
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Using join buffer (flat, BNL join)
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Using where; Using join buffer (flat, BNL join)
explain select * from t1, t1 t2 where t1.y = 8 and t2.x >= 7 and t2.x <= t1.y+0;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref y y 5 const 1
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Using join buffer (flat, BNL join)
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Using where; Using join buffer (flat, BNL join)
explain select * from t1, t1 t2 where t1.y = 2 and t2.x between t1.y-1 and t1.y+1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref y y 5 const 1
1 SIMPLE t2 range x x 5 NULL 3 Using index condition; Using join buffer (flat, BNL join)
1 SIMPLE t2 range x x 5 NULL 3 Using index condition; Using where; Using join buffer (flat, BNL join)
explain select * from t1, t1 t2 where t1.y = 2 and t2.x >= t1.y-1 and t2.x <= t1.y+1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref y y 5 const 1
1 SIMPLE t2 range x x 5 NULL 3 Using index condition; Using join buffer (flat, BNL join)
1 SIMPLE t2 range x x 5 NULL 3 Using index condition; Using where; Using join buffer (flat, BNL join)
explain select * from t1, t1 t2 where t1.y = 2 and t2.x between 0 and t1.y;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref y y 5 const 1
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Using join buffer (flat, BNL join)
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Using where; Using join buffer (flat, BNL join)
explain select * from t1, t1 t2 where t1.y = 2 and t2.x >= 0 and t2.x <= t1.y;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref y y 5 const 1
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Using join buffer (flat, BNL join)
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Using where; Using join buffer (flat, BNL join)
explain select count(*) from t1 where x in (1);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref x x 5 const 1 Using index

12
mysql-test/r/range_mrr_icp.result
View File

@ -223,27 +223,27 @@ update t1 set y=x;
explain select * from t1, t1 t2 where t1.y = 8 and t2.x between 7 and t1.y+0;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref y y 5 const 1
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Rowid-ordered scan; Using join buffer (flat, BNL join)
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Using where; Rowid-ordered scan; Using join buffer (flat, BNL join)
explain select * from t1, t1 t2 where t1.y = 8 and t2.x >= 7 and t2.x <= t1.y+0;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref y y 5 const 1
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Rowid-ordered scan; Using join buffer (flat, BNL join)
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Using where; Rowid-ordered scan; Using join buffer (flat, BNL join)
explain select * from t1, t1 t2 where t1.y = 2 and t2.x between t1.y-1 and t1.y+1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref y y 5 const 1
1 SIMPLE t2 range x x 5 NULL 3 Using index condition; Rowid-ordered scan; Using join buffer (flat, BNL join)
1 SIMPLE t2 range x x 5 NULL 3 Using index condition; Using where; Rowid-ordered scan; Using join buffer (flat, BNL join)
explain select * from t1, t1 t2 where t1.y = 2 and t2.x >= t1.y-1 and t2.x <= t1.y+1;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref y y 5 const 1
1 SIMPLE t2 range x x 5 NULL 3 Using index condition; Rowid-ordered scan; Using join buffer (flat, BNL join)
1 SIMPLE t2 range x x 5 NULL 3 Using index condition; Using where; Rowid-ordered scan; Using join buffer (flat, BNL join)
explain select * from t1, t1 t2 where t1.y = 2 and t2.x between 0 and t1.y;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref y y 5 const 1
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Rowid-ordered scan; Using join buffer (flat, BNL join)
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Using where; Rowid-ordered scan; Using join buffer (flat, BNL join)
explain select * from t1, t1 t2 where t1.y = 2 and t2.x >= 0 and t2.x <= t1.y;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref y y 5 const 1
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Rowid-ordered scan; Using join buffer (flat, BNL join)
1 SIMPLE t2 range x x 5 NULL 2 Using index condition; Using where; Rowid-ordered scan; Using join buffer (flat, BNL join)
explain select count(*) from t1 where x in (1);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ref x x 5 const 1 Using index

4
mysql-test/r/subselect_mat.result
View File

@ -1474,7 +1474,7 @@ EXPLAIN SELECT pk FROM t1 WHERE (a) IN (SELECT a FROM t2 WHERE pk > 0);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 4 func 1
2 MATERIALIZED t2 range PRIMARY PRIMARY 4 NULL 2 Using index condition; Rowid-ordered scan
2 MATERIALIZED t2 range PRIMARY PRIMARY 4 NULL 2 Using index condition; Using where; Rowid-ordered scan
SELECT pk FROM t1 WHERE (a) IN (SELECT a FROM t2 WHERE pk > 0);
pk
2
@ -2158,7 +2158,7 @@ EXPLAIN SELECT pk FROM t1 WHERE (a) IN (SELECT a FROM t2 WHERE pk > 0);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 4 func 1
2 MATERIALIZED t2 range PRIMARY PRIMARY 4 NULL 2 Using index condition
2 MATERIALIZED t2 range PRIMARY PRIMARY 4 NULL 2 Using index condition; Using where
SELECT pk FROM t1 WHERE (a) IN (SELECT a FROM t2 WHERE pk > 0);
pk
2

2
mysql-test/r/subselect_sj.result
View File

@ -803,7 +803,7 @@ EXPLAIN EXTENDED SELECT pk FROM t1 WHERE (a, b) IN (SELECT a, b FROM t2 WHERE pk
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2 100.00
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 11 func,func 1 100.00
2 MATERIALIZED t2 range PRIMARY PRIMARY 4 NULL 2 100.00 Using index condition; Rowid-ordered scan
2 MATERIALIZED t2 range PRIMARY PRIMARY 4 NULL 2 100.00 Using index condition; Using where; Rowid-ordered scan
Warnings:
Note 1003 select `test`.`t1`.`pk` AS `pk` from `test`.`t1` semi join (`test`.`t2`) where ((`test`.`t2`.`pk` > 0))
SELECT pk FROM t1 WHERE (a, b) IN (SELECT a, b FROM t2 WHERE pk > 0);

2
mysql-test/r/subselect_sj_jcl6.result
View File

@ -816,7 +816,7 @@ EXPLAIN EXTENDED SELECT pk FROM t1 WHERE (a, b) IN (SELECT a, b FROM t2 WHERE pk
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2 100.00
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 11 func,func 1 100.00
2 MATERIALIZED t2 range PRIMARY PRIMARY 4 NULL 2 100.00 Using index condition; Rowid-ordered scan
2 MATERIALIZED t2 range PRIMARY PRIMARY 4 NULL 2 100.00 Using index condition; Using where; Rowid-ordered scan
Warnings:
Note 1003 select `test`.`t1`.`pk` AS `pk` from `test`.`t1` semi join (`test`.`t2`) where ((`test`.`t2`.`pk` > 0))
SELECT pk FROM t1 WHERE (a, b) IN (SELECT a, b FROM t2 WHERE pk > 0);

2
mysql-test/r/subselect_sj_mat.result
View File

@ -1511,7 +1511,7 @@ EXPLAIN SELECT pk FROM t1 WHERE (a) IN (SELECT a FROM t2 WHERE pk > 0);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2
1 PRIMARY <subquery2> eq_ref distinct_key distinct_key 4 func 1
2 MATERIALIZED t2 range PRIMARY PRIMARY 4 NULL 2 Using index condition; Rowid-ordered scan
2 MATERIALIZED t2 range PRIMARY PRIMARY 4 NULL 2 Using index condition; Using where; Rowid-ordered scan
SELECT pk FROM t1 WHERE (a) IN (SELECT a FROM t2 WHERE pk > 0);
pk
2

44
mysql-test/t/join_cache.test
View File

@ -3636,5 +3636,49 @@ set optimizer_switch=@tmp_optimizer_switch;
DROP table t1,t2,t3;
--echo #
--echo # MDEV-5123 Remove duplicated conditions pushed both to join_tab->select_cond and join_tab->cache_select->cond for blocked joins.
--echo #
set join_cache_level=default;
set expensive_subquery_limit=0;
create table t1 (c1 int);
create table t2 (c2 int);
create table t3 (c3 int);
insert into t1 values (1), (2);
insert into t2 values (1), (2);
insert into t3 values (2);
explain
select count(*) from t1 straight_join t2
where c1 = c2-0 and c2 <= (select max(c3) from t3 where c3 = 2 and @counter:=@counter+1);
set @counter=0;
select count(*) from t1 straight_join t2
where c1 = c2-0 and c2 <= (select max(c3) from t3 where c3 = 2 and @counter:=@counter+1);
select @counter;
explain
select count(*) from t1 straight_join t2
where c1 = c2-0 and
c2 <= (select max(c3) from t3 where c3 = 2 and @counter:=@counter+1) and
c2 / 2 = 1;
set @counter=0;
select count(*) from t1 straight_join t2
where c1 = c2-0 and
c2 <= (select max(c3) from t3 where c3 = 2 and @counter:=@counter+1) and
c2 / 2 = 1;
select @counter;
drop table t1,t2,t3;
set expensive_subquery_limit=default;
# this must be the last command in the file
set @@optimizer_switch=@save_optimizer_switch;

2
mysql-test/t/limit_rows_examined.test
View File

@ -502,7 +502,7 @@ SELECT a AS field1, alias2.d AS field2, alias2.f AS field3, alias2.e AS field4,
FROM t1, t2 AS alias2, t2 AS alias3
WHERE alias3.c IN ( SELECT 1 UNION SELECT 6 )
GROUP BY field1, field2, field3, field4, field5
LIMIT ROWS EXAMINED 250;
LIMIT ROWS EXAMINED 124;
SHOW STATUS LIKE 'Handler_read%';
SHOW STATUS LIKE 'Handler_tmp%';

93
sql/sql_select.cc
View File

@ -10535,6 +10535,87 @@ restart:
}
}
/**
Remove pushdown conditions that are already checked by the scan phase
of BNL/BNLH joins.
@note
If the single-table condition for this table will be used by a
blocked join to pre-filter this table's rows, there is no need
to re-check the same single-table condition for each joined record.
This method removes from JOIN_TAB::select_cond and JOIN_TAB::select::cond
all top-level conjuncts that also appear in in JOIN_TAB::cache_select::cond.
*/
void JOIN_TAB::remove_redundant_bnl_scan_conds()
{
if (!(select_cond && cache_select && cache &&
(cache->get_join_alg() == JOIN_CACHE::BNL_JOIN_ALG ||
cache->get_join_alg() == JOIN_CACHE::BNLH_JOIN_ALG)))
return;
/*
select->cond is not processed separately. This method assumes it is always
the same as select_cond.
*/
DBUG_ASSERT(!select || !select->cond ||
(select->cond == select_cond));
if (is_cond_and(select_cond))
{
List_iterator<Item> pushed_cond_li(*((Item_cond*) select_cond)->argument_list());
Item *pushed_item;
Item_cond_and *reduced_select_cond= new Item_cond_and;
if (is_cond_and(cache_select->cond))
{
List_iterator<Item> scan_cond_li(*((Item_cond*) cache_select->cond)->argument_list());
Item *scan_item;
while ((pushed_item= pushed_cond_li++))
{
bool found= false;
scan_cond_li.rewind();
while ((scan_item= scan_cond_li++))
{
if (pushed_item->eq(scan_item, 0))
{
found= true;
break;
}
}
if (!found)
reduced_select_cond->add(pushed_item);
}
}
else
{
while ((pushed_item= pushed_cond_li++))
{
if (!pushed_item->eq(cache_select->cond, 0))
reduced_select_cond->add(pushed_item);
}
}
/*
JOIN_CACHE::check_match uses JOIN_TAB::select->cond instead of
JOIN_TAB::select_cond. set_cond() sets both pointers.
*/
if (reduced_select_cond->argument_list()->is_empty())
set_cond(NULL);
else if (reduced_select_cond->argument_list()->elements == 1)
set_cond(reduced_select_cond->argument_list()->head());
else
{
reduced_select_cond->quick_fix_field();
set_cond(reduced_select_cond);
}
}
else if (select_cond->eq(cache_select->cond, 0))
set_cond(NULL);
}
/*
Plan refinement stage: do various setup things for the executor
@ -10786,6 +10867,15 @@ make_join_readinfo(JOIN *join, ulonglong options, uint no_jbuf_after)
abort();
/* purecov: end */
}
tab->remove_redundant_bnl_scan_conds();
DBUG_EXECUTE("where",
char buff[256];
String str(buff,sizeof(buff),system_charset_info);
str.length(0);
str.append(tab->table? tab->table->alias.c_ptr() :"<no_table_name>");
str.append(" final_pushdown_cond");
print_where(tab->select_cond, str.c_ptr_safe(), QT_ORDINARY););
}
uint n_top_tables= join->join_tab_ranges.head()->end -
join->join_tab_ranges.head()->start;
@ -23201,7 +23291,8 @@ int JOIN::save_explain_data_intern(Explain_query *output, bool need_tmp_table,
eta->push_extra(ET_RANGE_CHECKED_FOR_EACH_RECORD);
eta->range_checked_map= tab->keys;
}
else if (tab->select->cond)
else if (tab->select->cond ||
(tab->cache_select && tab->cache_select->cond))
{
const COND *pushed_cond= tab->table->file->pushed_cond;

1
sql/sql_select.h
View File

@ -544,6 +544,7 @@ typedef struct st_join_table {
!(used_sjm_lookup_tables & ~emb_sj_nest->sj_inner_tables));
}
void remove_redundant_bnl_scan_conds();
} JOIN_TAB;