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Fixed bug mdev-10884.

Browse source 
If a materialized derived table / view is specified by a unit
with SELECTs containing ORDER BY ... LIMIT then condition pushdown
cannot be done for these SELECTs.
If a materialized derived table / view is specified by a unit
containing global ORDER BY ... LIMIT then condition pushdown
cannot be done for this unit.
This commit is contained in:
Igor Babaev 2016-09-25 17:28:49 -07:00
commit 1f1990a161
4 changed files with 95 additions and 12 deletions
Download patch file Download diff file Expand all files Collapse all files

51
mysql-test/r/derived_cond_pushdown.result
View file

@ -7032,3 +7032,54 @@ i
DROP FUNCTION f;
DROP VIEW v2,v1;
DROP TABLE t1;
#
# MDEV-10884: condition pushdown into derived specified by
# 1. unit with SELECT containing ORDER BY ... LIMIT
# 2. unit containing global ORDER BY ... LIMIT
#
create table t1(a int);
insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
select a from t1 order by a limit 5;
a
0
1
2
3
4
set statement optimizer_switch='condition_pushdown_for_derived=off' for
select * from (select a from t1 order by a limit 5) t where t.a not in (1,2,3);
a
0
4
set statement optimizer_switch='condition_pushdown_for_derived=on' for
select * from (select a from t1 order by a limit 5) t where t.a not in (1,2,3);
a
0
4
select a from t1 where a < 4 union select a from t1 where a > 5
order by a limit 5;
a
0
1
2
3
6
set statement optimizer_switch='condition_pushdown_for_derived=off' for
select * from
(select a from t1 where a < 4 union select a from t1 where a > 5
order by a limit 5) t where t.a not in (2,9);
a
0
1
3
6
set statement optimizer_switch='condition_pushdown_for_derived=on' for
select * from
(select a from t1 where a < 4 union select a from t1 where a > 5
order by a limit 5) t where t.a not in (2,9);
a
0
1
3
6
drop table t1;

28
mysql-test/t/derived_cond_pushdown.test
View file

@ -923,3 +923,31 @@ EXECUTE stmt;
DROP FUNCTION f;
DROP VIEW v2,v1;
DROP TABLE t1;
--echo #
--echo # MDEV-10884: condition pushdown into derived specified by
--echo # 1. unit with SELECT containing ORDER BY ... LIMIT
--echo # 2. unit containing global ORDER BY ... LIMIT
--echo #
create table t1(a int);
insert into t1 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
select a from t1 order by a limit 5;
set statement optimizer_switch='condition_pushdown_for_derived=off' for
select * from (select a from t1 order by a limit 5) t where t.a not in (1,2,3);
set statement optimizer_switch='condition_pushdown_for_derived=on' for
select * from (select a from t1 order by a limit 5) t where t.a not in (1,2,3);
select a from t1 where a < 4 union select a from t1 where a > 5
order by a limit 5;
set statement optimizer_switch='condition_pushdown_for_derived=off' for
select * from
(select a from t1 where a < 4 union select a from t1 where a > 5
order by a limit 5) t where t.a not in (2,9);
set statement optimizer_switch='condition_pushdown_for_derived=on' for
select * from
(select a from t1 where a < 4 union select a from t1 where a > 5
order by a limit 5) t where t.a not in (2,9);
drop table t1;

30
sql/sql_derived.cc
View file

@ -1131,19 +1131,6 @@ bool pushdown_cond_for_derived(THD *thd, Item *cond, TABLE_LIST *derived)
st_select_lex_unit *unit= derived->get_unit();
st_select_lex *sl= unit->first_select();
/* Check whether any select of 'unit' allows condition pushdown */
bool any_select_allows_cond_pushdown= false;
for (; sl; sl= sl->next_select())
{
if (sl->cond_pushdown_is_allowed())
{
any_select_allows_cond_pushdown= true;
break;
}
}
if (!any_select_allows_cond_pushdown)
return false;
/* Do not push conditions into constant derived */
if (unit->executed)
return false;
@ -1152,6 +1139,23 @@ bool pushdown_cond_for_derived(THD *thd, Item *cond, TABLE_LIST *derived)
if (derived->is_recursive_with_table())
return false;
/* Do not push conditions into unit with global ORDER BY ... LIMIT */
if (unit->fake_select_lex && unit->fake_select_lex->explicit_limit)
return false;
/* Check whether any select of 'unit' allows condition pushdown */
bool some_select_allows_cond_pushdown= false;
for (; sl; sl= sl->next_select())
{
if (sl->cond_pushdown_is_allowed())
{
some_select_allows_cond_pushdown= true;
break;
}
}
if (!some_select_allows_cond_pushdown)
return false;
/*
Build the most restrictive condition extractable from 'cond'
that can be pushed into the derived table 'derived'.

2
sql/sql_lex.h
View file

@ -1160,7 +1160,7 @@ public:
bool have_window_funcs() const { return (window_funcs.elements !=0); }
bool cond_pushdown_is_allowed() const
{ return !have_window_funcs() && !olap; }
{ return !have_window_funcs() && !olap && !explicit_limit; }
private:
bool m_non_agg_field_used;