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Commit a765b19e authored by Galina Shalygina's avatar Galina Shalygina
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MDEV-19245: Impossible WHERE should be noticed earlier after HAVING pushdown 

The bug appears because not all conditions are found to be knowingly
true or false in WHERE after HAVING pushdown optimization.
Impossible WHERE can be found much earlier compared with how it is done now.

To fix it and_new_conditions_to_optimized_cond() is changed.
parent a65d3b2c
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Showing with 89 additions and 12 deletions
mysql-test/main/having_cond_pushdown.result
View file @ a765b19e
......@@ -4733,3 +4733,46 @@ EXPLAIN
}
}
drop table t1;
#
# MDEV-19245: Impossible WHERE should be noticed earlier
# after HAVING pushdown
#
CREATE TABLE t1 (a INT, b INT, c INT);
INSERT INTO t1 VALUES (1,2,1),(3,2,2),(5,6,4),(3,4,1);
EXPLAIN SELECT t1.a,MAX(t1.b) FROM t1
WHERE t1.a > 3 GROUP BY t1.a HAVING t1.a = 3;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
EXPLAIN SELECT t1.a,MAX(t1.b) FROM t1
WHERE t1.a = 3 GROUP BY t1.a HAVING t1.a > 3;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
EXPLAIN SELECT t1.a,MAX(t1.b) FROM t1
WHERE t1.a > 3 AND t1.a = 3 GROUP BY t1.a ;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
EXPLAIN SELECT t1.a,MAX(t1.b) FROM t1
WHERE (t1.a < 2 OR t1.c > 1) GROUP BY t1.a HAVING t1.a = 3;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 4 Using where
EXPLAIN SELECT t1.a,MAX(t1.b) FROM t1
WHERE t1.a = 3 GROUP BY t1.a HAVING (t1.a < 2 OR t1.a > 3);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
EXPLAIN SELECT t1.a,MAX(t1.b) FROM t1
WHERE t1.a = 3 AND (t1.a < 2 OR t1.a > 3) GROUP BY t1.a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
EXPLAIN SELECT t1.a,MAX(t1.b),t1.c FROM t1
WHERE (t1.a < 2 AND t1.c > 1) GROUP BY t1.a HAVING t1.a = 3;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
EXPLAIN SELECT t1.a,MAX(t1.b),t1.c FROM t1
WHERE t1.a = 3 GROUP BY t1.a HAVING (t1.a < 2 AND t1.c > 1);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
EXPLAIN SELECT t1.a,MAX(t1.b),t1.c FROM t1
WHERE t1.a = 3 AND (t1.a < 2 AND t1.b > 3) GROUP BY t1.a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE NULL NULL NULL NULL NULL NULL NULL Impossible WHERE
DROP TABLE t1;
mysql-test/main/having_cond_pushdown.test
View file @ a765b19e
......@@ -1370,3 +1370,34 @@ eval explain extended $q2;
eval explain format=json $q2;
drop table t1;
--echo #
--echo # MDEV-19245: Impossible WHERE should be noticed earlier
--echo # after HAVING pushdown
--echo #
CREATE TABLE t1 (a INT, b INT, c INT);
INSERT INTO t1 VALUES (1,2,1),(3,2,2),(5,6,4),(3,4,1);
EXPLAIN SELECT t1.a,MAX(t1.b) FROM t1
WHERE t1.a > 3 GROUP BY t1.a HAVING t1.a = 3;
EXPLAIN SELECT t1.a,MAX(t1.b) FROM t1
WHERE t1.a = 3 GROUP BY t1.a HAVING t1.a > 3;
EXPLAIN SELECT t1.a,MAX(t1.b) FROM t1
WHERE t1.a > 3 AND t1.a = 3 GROUP BY t1.a ;
EXPLAIN SELECT t1.a,MAX(t1.b) FROM t1
WHERE (t1.a < 2 OR t1.c > 1) GROUP BY t1.a HAVING t1.a = 3;
EXPLAIN SELECT t1.a,MAX(t1.b) FROM t1
WHERE t1.a = 3 GROUP BY t1.a HAVING (t1.a < 2 OR t1.a > 3);
EXPLAIN SELECT t1.a,MAX(t1.b) FROM t1
WHERE t1.a = 3 AND (t1.a < 2 OR t1.a > 3) GROUP BY t1.a;
EXPLAIN SELECT t1.a,MAX(t1.b),t1.c FROM t1
WHERE (t1.a < 2 AND t1.c > 1) GROUP BY t1.a HAVING t1.a = 3;
EXPLAIN SELECT t1.a,MAX(t1.b),t1.c FROM t1
WHERE t1.a = 3 GROUP BY t1.a HAVING (t1.a < 2 AND t1.c > 1);
EXPLAIN SELECT t1.a,MAX(t1.b),t1.c FROM t1
WHERE t1.a = 3 AND (t1.a < 2 AND t1.b > 3) GROUP BY t1.a;
DROP TABLE t1;
sql/item.h
View file @ a765b19e
......@@ -1947,6 +1947,12 @@ class Item: public Value_source,
virtual bool check_partition_func_processor(void *arg) { return 1;}
virtual bool post_fix_fields_part_expr_processor(void *arg) { return 0; }
virtual bool rename_fields_processor(void *arg) { return 0; }
/*
TRUE if the function is knowingly TRUE or FALSE.
Not to be used for AND/OR formulas.
*/
virtual bool is_simplified_cond_processor(void *arg) { return false; }
/** Processor used to check acceptability of an item in the defining
expression for a virtual column
......
sql/item_func.h
View file @ a765b19e
......@@ -398,6 +398,8 @@ class Item_func :public Item_func_or_sum,
bool with_sum_func() const { return m_with_sum_func; }
With_sum_func_cache* get_with_sum_func_cache() { return this; }
Item_func *get_item_func() { return this; }
bool is_simplified_cond_processor(void *arg)
{ return const_item() && !val_int(); }
};
......
sql/opt_subselect.cc
View file @ a765b19e
......@@ -5723,12 +5723,6 @@ Item *and_new_conditions_to_optimized_cond(THD *thd, Item *cond,
&((Item_cond_and *) cond)->m_cond_equal,
false, NULL);
}
/*
Check if equalities that can't be transformed into multiple
equalities are knowingly true or false.
*/
if (item->const_item() && !item->val_int())
is_simplified_cond= true;
and_args->push_back(item, thd->mem_root);
}
and_args->append((List<Item> *) cond_equalities);
......@@ -5821,12 +5815,6 @@ Item *and_new_conditions_to_optimized_cond(THD *thd, Item *cond,
{
item= item->build_equal_items(thd, inherited, false, NULL);
}
/*
Check if equalities that can't be transformed into multiple
equalities are knowingly true or false.
*/
if (item->const_item() && !item->val_int())
is_simplified_cond= true;
new_conds_list.push_back(item, thd->mem_root);
}
new_conds_list.append((List<Item> *)&new_cond_equal.current_level);
......@@ -5870,7 +5858,14 @@ Item *and_new_conditions_to_optimized_cond(THD *thd, Item *cond,
cond= cond->propagate_equal_fields(thd,
Item::Context_boolean(),
*cond_eq);
cond->update_used_tables();
}
/* Check if conds has knowingly true or false parts. */
if (cond &&
!is_simplified_cond &&
cond->walk(&Item::is_simplified_cond_processor, 0, 0))
is_simplified_cond= true;
/*
If it was found that there are some knowingly true or false equalities
......
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