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Merge olga.mysql.com:/home/igor/mysql-4.1-opt

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into  olga.mysql.com:/home/igor/mysql-5.0-opt
This commit is contained in:
igor@olga.mysql.com 2006-12-12 11:53:09 -08:00
commit 11cdca9a2f
4 changed files with 44 additions and 3 deletions
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13
mysql-test/r/subselect.result
View File

@ -3033,6 +3033,19 @@ t3 CREATE TABLE `t3` (
`a` datetime default NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
DROP TABLE t1,t2,t3;
CREATE TABLE t1 (a int);
INSERT INTO t1 VALUES (1), (2);
SELECT a FROM t1 WHERE (SELECT 1 FROM DUAL WHERE 1=0) > 0;
a
SELECT a FROM t1 WHERE (SELECT 1 FROM DUAL WHERE 1=0) IS NULL;
a
1
2
EXPLAIN SELECT a FROM t1 WHERE (SELECT 1 FROM DUAL WHERE 1=0) IS NULL;
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 2
2 SUBQUERY NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
DROP TABLE t1;
create table t1 (df decimal(5,1));
insert into t1 values(1.1);
insert into t1 values(2.2);

12
mysql-test/t/subselect.test
View File

@ -1988,6 +1988,18 @@ SHOW CREATE TABLE t3;
DROP TABLE t1,t2,t3;
#
# Bug 24670: subquery witout tables but with a WHERE clause
#
CREATE TABLE t1 (a int);
INSERT INTO t1 VALUES (1), (2);
SELECT a FROM t1 WHERE (SELECT 1 FROM DUAL WHERE 1=0) > 0;
SELECT a FROM t1 WHERE (SELECT 1 FROM DUAL WHERE 1=0) IS NULL;
EXPLAIN SELECT a FROM t1 WHERE (SELECT 1 FROM DUAL WHERE 1=0) IS NULL;
DROP TABLE t1;
# End of 4.1 tests
#

19
sql/item_subselect.cc
View File

@ -349,6 +349,7 @@ Item_singlerow_subselect::select_transformer(JOIN *join)
*/
!(select_lex->item_list.head()->type() == FIELD_ITEM ||
select_lex->item_list.head()->type() == REF_ITEM) &&
!join->conds && !join->having &&
/*
switch off this optimization for prepare statement,
because we do not rollback this changes
@ -373,8 +374,6 @@ Item_singlerow_subselect::select_transformer(JOIN *join)
*/
substitution->walk(&Item::remove_dependence_processor,
(byte *) select_lex->outer_select());
/* SELECT without FROM clause can't have WHERE or HAVING clause */
DBUG_ASSERT(join->conds == 0 && join->having == 0);
return RES_REDUCE;
}
return RES_OK;
@ -2277,6 +2276,22 @@ bool subselect_single_select_engine::no_tables()
}
/*
Check statically whether the subquery can return NULL
SINOPSYS
subselect_single_select_engine::may_be_null()
RETURN
FALSE can guarantee that the subquery never return NULL
TRUE otherwise
*/
bool subselect_single_select_engine::may_be_null()
{
return ((no_tables() && !join->conds && !join->having) ? maybe_null : 1);
}
/*
Report about presence of tables in subquery

3
sql/item_subselect.h
View File

@ -363,7 +363,7 @@ public:
enum Item_result type() { return res_type; }
enum_field_types field_type() { return res_field_type; }
virtual void exclude()= 0;
bool may_be_null() { return maybe_null; };
virtual bool may_be_null() { return maybe_null; };
virtual table_map upper_select_const_tables()= 0;
static table_map calc_const_tables(TABLE_LIST *);
virtual void print(String *str)= 0;
@ -400,6 +400,7 @@ public:
void print (String *str);
bool change_result(Item_subselect *si, select_subselect *result);
bool no_tables();
bool may_be_null();
bool is_executed() const { return executed; }
bool no_rows();
};