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MDEV-29294 Assertion `functype() == ((Item_cond *) new_item)->functype()' failed in Item_cond::remove_eq_conds on SELECT

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Item_singlerow_subselect may be converted to Item_cond during
optimization. So there is a possibility of constructing nested
Item_cond_and or Item_cond_or which is not allowed (such
conditions must be flattened).
This commit checks if such kind of optimization has been applied
and flattens the condition if needed
This commit is contained in:
Oleg Smirnov 2023-01-12 13:18:33 +07:00
parent c256998b6e
commit afb5deb9db
6 changed files with 268 additions and 26 deletions
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56
mysql-test/main/select.result
View File

@ -5639,4 +5639,60 @@ EXECUTE stmt;
COUNT(DISTINCT a)
3
DROP TABLE t1;
#
# MDEV-29294: Assertion `functype() == ((Item_cond *) new_item)->functype()'
# failed in Item_cond::remove_eq_conds on SELECT
#
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (1),(2),(3);
# Test for nested OR conditions:
SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3));
a
1
EXPLAIN EXTENDED
SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3));
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 3 100.00 Using where; Using temporary
3 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL NULL No tables used
Warnings:
Note 1276 Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
Note 1276 Field or reference 'test.t1.a' of SELECT #3 was resolved in SELECT #1
Note 1276 Field or reference 'test.t1.a' of SELECT #3 was resolved in SELECT #1
Note 1249 Select 2 was reduced during optimization
Note 1003 /* select#1 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` = 1 and (1 or <expr_cache><`test`.`t1`.`a`>((/* select#3 */ select 3 from DUAL where `test`.`t1`.`a` = `test`.`t1`.`a`)) = 3)
PREPARE stmt FROM 'SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3))';
EXECUTE stmt;
a
1
EXECUTE stmt;
a
1
CREATE VIEW v1 AS SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3));
SELECT * FROM v1;
a
1
# Test for nested AND conditions:
SELECT * FROM t1 WHERE a = 1 OR
(3 = 3 AND (SELECT a = 1 AND (SELECT 3 WHERE a = a) = 3));
a
1
PREPARE stmt FROM 'SELECT * FROM t1 WHERE a = 1 OR
(3 = 3 AND (SELECT a = 1 AND (SELECT 3 WHERE a = a) = 3))';
EXECUTE stmt;
a
1
EXECUTE stmt;
a
1
CREATE VIEW v2 AS SELECT * FROM t1 WHERE a = 1 OR
(3 = 3 AND (SELECT a = 1 AND (SELECT 3 WHERE a = a) = 3));
SELECT * FROM v2;
a
1
DROP TABLE t1;
DROP VIEW v1, v2;
End of 10.0 tests

40
mysql-test/main/select.test
View File

@ -4742,4 +4742,44 @@ EXECUTE stmt;
--enable_warnings
DROP TABLE t1;
--echo #
--echo # MDEV-29294: Assertion `functype() == ((Item_cond *) new_item)->functype()'
--echo # failed in Item_cond::remove_eq_conds on SELECT
--echo #
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (1),(2),(3);
--echo # Test for nested OR conditions:
SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3));
EXPLAIN EXTENDED
SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3));
PREPARE stmt FROM 'SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3))';
EXECUTE stmt;
EXECUTE stmt;
CREATE VIEW v1 AS SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3));
SELECT * FROM v1;
--echo # Test for nested AND conditions:
SELECT * FROM t1 WHERE a = 1 OR
(3 = 3 AND (SELECT a = 1 AND (SELECT 3 WHERE a = a) = 3));
PREPARE stmt FROM 'SELECT * FROM t1 WHERE a = 1 OR
(3 = 3 AND (SELECT a = 1 AND (SELECT 3 WHERE a = a) = 3))';
EXECUTE stmt;
EXECUTE stmt;
CREATE VIEW v2 AS SELECT * FROM t1 WHERE a = 1 OR
(3 = 3 AND (SELECT a = 1 AND (SELECT 3 WHERE a = a) = 3));
SELECT * FROM v2;
DROP TABLE t1;
DROP VIEW v1, v2;
--echo End of 10.0 tests

56
mysql-test/main/select_jcl6.result
View File

@ -5650,6 +5650,62 @@ EXECUTE stmt;
COUNT(DISTINCT a)
3
DROP TABLE t1;
#
# MDEV-29294: Assertion `functype() == ((Item_cond *) new_item)->functype()'
# failed in Item_cond::remove_eq_conds on SELECT
#
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (1),(2),(3);
# Test for nested OR conditions:
SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3));
a
1
EXPLAIN EXTENDED
SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3));
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 3 100.00 Using where; Using temporary
3 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL NULL No tables used
Warnings:
Note 1276 Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
Note 1276 Field or reference 'test.t1.a' of SELECT #3 was resolved in SELECT #1
Note 1276 Field or reference 'test.t1.a' of SELECT #3 was resolved in SELECT #1
Note 1249 Select 2 was reduced during optimization
Note 1003 /* select#1 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` = 1 and (1 or <expr_cache><`test`.`t1`.`a`>((/* select#3 */ select 3 from DUAL where `test`.`t1`.`a` = `test`.`t1`.`a`)) = 3)
PREPARE stmt FROM 'SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3))';
EXECUTE stmt;
a
1
EXECUTE stmt;
a
1
CREATE VIEW v1 AS SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3));
SELECT * FROM v1;
a
1
# Test for nested AND conditions:
SELECT * FROM t1 WHERE a = 1 OR
(3 = 3 AND (SELECT a = 1 AND (SELECT 3 WHERE a = a) = 3));
a
1
PREPARE stmt FROM 'SELECT * FROM t1 WHERE a = 1 OR
(3 = 3 AND (SELECT a = 1 AND (SELECT 3 WHERE a = a) = 3))';
EXECUTE stmt;
a
1
EXECUTE stmt;
a
1
CREATE VIEW v2 AS SELECT * FROM t1 WHERE a = 1 OR
(3 = 3 AND (SELECT a = 1 AND (SELECT 3 WHERE a = a) = 3));
SELECT * FROM v2;
a
1
DROP TABLE t1;
DROP VIEW v1, v2;
End of 10.0 tests
set join_cache_level=default;
set @@optimizer_switch=@save_optimizer_switch_jcl6;

56
mysql-test/main/select_pkeycache.result
View File

@ -5639,4 +5639,60 @@ EXECUTE stmt;
COUNT(DISTINCT a)
3
DROP TABLE t1;
#
# MDEV-29294: Assertion `functype() == ((Item_cond *) new_item)->functype()'
# failed in Item_cond::remove_eq_conds on SELECT
#
CREATE TABLE t1 (a INT);
INSERT INTO t1 VALUES (1),(2),(3);
# Test for nested OR conditions:
SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3));
a
1
EXPLAIN EXTENDED
SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3));
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY t1 ALL NULL NULL NULL NULL 3 100.00 Using where; Using temporary
3 DEPENDENT SUBQUERY NULL NULL NULL NULL NULL NULL NULL NULL No tables used
Warnings:
Note 1276 Field or reference 'test.t1.a' of SELECT #2 was resolved in SELECT #1
Note 1276 Field or reference 'test.t1.a' of SELECT #3 was resolved in SELECT #1
Note 1276 Field or reference 'test.t1.a' of SELECT #3 was resolved in SELECT #1
Note 1249 Select 2 was reduced during optimization
Note 1003 /* select#1 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where `test`.`t1`.`a` = 1 and (1 or <expr_cache><`test`.`t1`.`a`>((/* select#3 */ select 3 from DUAL where `test`.`t1`.`a` = `test`.`t1`.`a`)) = 3)
PREPARE stmt FROM 'SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3))';
EXECUTE stmt;
a
1
EXECUTE stmt;
a
1
CREATE VIEW v1 AS SELECT * FROM t1 WHERE a = 1 AND
(3 = 0 OR (SELECT a = 1 OR (SELECT 3 WHERE a = a) = 3));
SELECT * FROM v1;
a
1
# Test for nested AND conditions:
SELECT * FROM t1 WHERE a = 1 OR
(3 = 3 AND (SELECT a = 1 AND (SELECT 3 WHERE a = a) = 3));
a
1
PREPARE stmt FROM 'SELECT * FROM t1 WHERE a = 1 OR
(3 = 3 AND (SELECT a = 1 AND (SELECT 3 WHERE a = a) = 3))';
EXECUTE stmt;
a
1
EXECUTE stmt;
a
1
CREATE VIEW v2 AS SELECT * FROM t1 WHERE a = 1 OR
(3 = 3 AND (SELECT a = 1 AND (SELECT 3 WHERE a = a) = 3));
SELECT * FROM v2;
a
1
DROP TABLE t1;
DROP VIEW v1, v2;
End of 10.0 tests

83
sql/item_cmpfunc.cc
View File

@ -4816,38 +4816,18 @@ Item_cond::fix_fields(THD *thd, Item **ref)
if (check_stack_overrun(thd, STACK_MIN_SIZE, buff))
return TRUE; // Fatal error flag is set!
/*
The following optimization reduces the depth of an AND-OR tree.
E.g. a WHERE clause like
F1 AND (F2 AND (F2 AND F4))
is parsed into a tree with the same nested structure as defined
by braces. This optimization will transform such tree into
AND (F1, F2, F3, F4).
Trees of OR items are flattened as well:
((F1 OR F2) OR (F3 OR F4)) => OR (F1, F2, F3, F4)
Items for removed AND/OR levels will dangle until the death of the
entire statement.
The optimization is currently prepared statements and stored procedures
friendly as it doesn't allocate any memory and its effects are durable
(i.e. do not depend on PS/SP arguments).
*/
while ((item=li++))
while (li++)
{
while (item->type() == Item::COND_ITEM &&
((Item_cond*) item)->functype() == functype() &&
!((Item_cond*) item)->list.is_empty())
{ // Identical function
li.replace(((Item_cond*) item)->list);
((Item_cond*) item)->list.empty();
item= *li.ref(); // new current item
}
merge_sub_condition(li);
item= *li.ref();
if (abort_on_null)
item->top_level_item();
/*
replace degraded condition:
was: <field>
become: <field> = 1
become: <field> != 0
*/
Item::Type type= item->type();
if (type == Item::FIELD_ITEM || type == Item::REF_ITEM)
@ -4863,7 +4843,9 @@ Item_cond::fix_fields(THD *thd, Item **ref)
if (item->fix_fields_if_needed_for_bool(thd, li.ref()))
return TRUE; /* purecov: inspected */
item= *li.ref(); // item can be substituted in fix_fields
merge_sub_condition(li);
item= *li.ref(); // may be substituted in fix_fields/merge_item_if_possible
used_tables_cache|= item->used_tables();
if (item->const_item() && !item->with_param &&
!item->is_expensive() && !cond_has_datetime_is_null(item))
@ -4915,6 +4897,55 @@ Item_cond::fix_fields(THD *thd, Item **ref)
return FALSE;
}
/**
@brief
Merge a lower-level condition pointed by the iterator into this Item_cond
if possible
@param li list iterator pointing to condition that must be
examined and merged if possible.
@details
If an item pointed by the iterator is an instance of Item_cond with the
same functype() as this Item_cond (i.e. both are Item_cond_and or both are
Item_cond_or) then the arguments of that lower-level item can be merged
into the list of arguments of this upper-level Item_cond.
This optimization reduces the depth of an AND-OR tree.
E.g. a WHERE clause like
F1 AND (F2 AND (F2 AND F4))
is parsed into a tree with the same nested structure as defined
by braces. This optimization will transform such tree into
AND (F1, F2, F3, F4).
Trees of OR items are flattened as well:
((F1 OR F2) OR (F3 OR F4)) => OR (F1, F2, F3, F4)
Items for removed AND/OR levels will dangle until the death of the
entire statement.
The optimization is currently prepared statements and stored procedures
friendly as it doesn't allocate any memory and its effects are durable
(i.e. do not depend on PS/SP arguments).
*/
void Item_cond::merge_sub_condition(List_iterator<Item>& li)
{
Item *item= *li.ref();
/*
The check for list.is_empty() is to catch empty Item_cond_and() items.
We may encounter Item_cond_and with an empty list, because optimizer code
strips multiple equalities, combines items, then adds multiple equalities
back
*/
while (item->type() == Item::COND_ITEM &&
((Item_cond*) item)->functype() == functype() &&
!((Item_cond*) item)->list.is_empty())
{
li.replace(((Item_cond*) item)->list);
((Item_cond*) item)->list.empty();
item= *li.ref();
}
}
bool
Item_cond::eval_not_null_tables(void *opt_arg)

3
sql/item_cmpfunc.h
View File

@ -3046,6 +3046,9 @@ public:
Item *build_clone(THD *thd);
bool excl_dep_on_table(table_map tab_map);
bool excl_dep_on_grouping_fields(st_select_lex *sel);
private:
void merge_sub_condition(List_iterator<Item>& li);
};
template <template<class> class LI, class T> class Item_equal_iterator;