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Fixed bug #57024.

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The condition over the outer tables now are extracted from
the on condition of any outer join. This condition is
saved in a special field of the JOIN_TAB structure for
the first inner table of the outer join. The condition
is checked before the first inner table is accessed. If 
it turns out to be false the table is not accessed at all
and a null complemented row is generated immediately.
This commit is contained in:
Igor Babaev 2010-09-26 09:12:34 -07:00
parent d91422f03a
commit 716e84164a
4 changed files with 124 additions and 11 deletions
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59
mysql-test/r/join_outer.result
View File

@ -1449,4 +1449,63 @@ group by t2.pk;
pk t
2001 3001
drop table t1,t2,t3,t4;
#
# Bug#57024: Poor performance when conjunctive condition over the outer
# table is used in the on condition of an outer join
#
create table t1 (a int);
insert into t1 values (NULL), (NULL), (NULL), (NULL);
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 values (4), (2), (1), (3);
create table t2 like t1;
insert into t2 select if(t1.a is null, 10, t1.a) from t1;
create table t3 (a int, b int, index idx(a));
insert into t3 values (1, 100), (3, 301), (4, 402), (1, 102), (1, 101);
analyze table t1,t2,t3;
Table Op Msg_type Msg_text
test.t1 analyze status OK
test.t2 analyze status OK
test.t3 analyze status OK
flush status;
select sum(t3.b) from t1 left join t3 on t3.a=t1.a and t1.a is not null;
sum(t3.b)
1006
show status like "handler_read%";
Variable_name Value
Handler_read_first 0
Handler_read_key 4
Handler_read_next 5
Handler_read_prev 0
Handler_read_rnd 0
Handler_read_rnd_next 1048581
flush status;
select sum(t3.b) from t2 left join t3 on t3.a=t2.a and t2.a <> 10;
sum(t3.b)
1006
show status like "handler_read%";
Variable_name Value
Handler_read_first 0
Handler_read_key 4
Handler_read_next 5
Handler_read_prev 0
Handler_read_rnd 0
Handler_read_rnd_next 1048581
drop table t1,t2,t3;
End of 5.1 tests

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

@ -1029,4 +1029,48 @@ select t2.pk,
drop table t1,t2,t3,t4;
--echo #
--echo # Bug#57024: Poor performance when conjunctive condition over the outer
--echo # table is used in the on condition of an outer join
--echo #
create table t1 (a int);
insert into t1 values (NULL), (NULL), (NULL), (NULL);
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 select * from t1;
insert into t1 values (4), (2), (1), (3);
create table t2 like t1;
insert into t2 select if(t1.a is null, 10, t1.a) from t1;
create table t3 (a int, b int, index idx(a));
insert into t3 values (1, 100), (3, 301), (4, 402), (1, 102), (1, 101);
analyze table t1,t2,t3;
flush status;
select sum(t3.b) from t1 left join t3 on t3.a=t1.a and t1.a is not null;
show status like "handler_read%";
flush status;
select sum(t3.b) from t2 left join t3 on t3.a=t2.a and t2.a <> 10;
show status like "handler_read%";
drop table t1,t2,t3;
--echo End of 5.1 tests

28
sql/sql_select.cc
View File

@ -6632,6 +6632,9 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
if (tmp_cond)
{
JOIN_TAB *cond_tab= tab < first_inner_tab ? first_inner_tab : tab;
Item **sel_cond_ref= tab < first_inner_tab ?
&first_inner_tab->on_precond :
&tab->select_cond;
/*
First add the guards for match variables of
all embedding outer join operations.
@ -6654,14 +6657,14 @@ make_join_select(JOIN *join,SQL_SELECT *select,COND *cond)
tmp_cond->quick_fix_field();
/* Add the predicate to other pushed down predicates */
DBUG_PRINT("info", ("Item_cond_and"));
cond_tab->select_cond= !cond_tab->select_cond ? tmp_cond :
new Item_cond_and(cond_tab->select_cond,
tmp_cond);
*sel_cond_ref= !(*sel_cond_ref) ?
tmp_cond :
new Item_cond_and(*sel_cond_ref, tmp_cond);
DBUG_PRINT("info", ("Item_cond_and 0x%lx",
(ulong)cond_tab->select_cond));
if (!cond_tab->select_cond)
DBUG_RETURN(1);
cond_tab->select_cond->quick_fix_field();
(ulong)(*sel_cond_ref)));
if (!(*sel_cond_ref))
DBUG_RETURN(1);
(*sel_cond_ref)->quick_fix_field();
}
}
first_inner_tab= first_inner_tab->first_upper;
@ -11646,7 +11649,7 @@ sub_select(JOIN *join,JOIN_TAB *join_tab,bool end_of_records)
return (*join_tab->next_select)(join,join_tab+1,end_of_records);
int error;
enum_nested_loop_state rc;
enum_nested_loop_state rc= NESTED_LOOP_OK;
READ_RECORD *info= &join_tab->read_record;
if (join->resume_nested_loop)
@ -11674,11 +11677,16 @@ sub_select(JOIN *join,JOIN_TAB *join_tab,bool end_of_records)
/* Set first_unmatched for the last inner table of this group */
join_tab->last_inner->first_unmatched= join_tab;
if (join_tab->on_precond && !join_tab->on_precond->val_int())
rc= NESTED_LOOP_NO_MORE_ROWS;
}
join->thd->row_count= 0;
error= (*join_tab->read_first_record)(join_tab);
rc= evaluate_join_record(join, join_tab, error);
if (rc != NESTED_LOOP_NO_MORE_ROWS)
{
error= (*join_tab->read_first_record)(join_tab);
rc= evaluate_join_record(join, join_tab, error);
}
}
while (rc == NESTED_LOOP_OK)

4
sql/sql_select.h
View File

@ -154,7 +154,9 @@ typedef struct st_join_table {
TABLE *table;
KEYUSE *keyuse; /**< pointer to first used key */
SQL_SELECT *select;
COND *select_cond;
COND *select_cond;
COND *on_precond; /**< part of on condition to check before
accessing the first inner table */
QUICK_SELECT_I *quick;
Item **on_expr_ref; /**< pointer to the associated on expression */
COND_EQUAL *cond_equal; /**< multiple equalities for the on expression */