Fix bug lp:1002079

  
  Analysis:
  The optimizer detects an empty result through constant table optimization.
  Then it calls return_zero_rows(), which in turns calls inderctly
  Item_maxmin_subselect::no_rows_in_result(). The latter method set "value=0",
  however "value" is pointer to Item_cache, and not just an integer value.
  
  All of the Item_[maxmin | singlerow]_subselect::val_XXX methods does:
    if (forced_const)
      return value->val_real();
  which of course crashes when value is a NULL pointer.
  
  Solution:
  When the optimizer discovers an empty result set, set
  Item_singlerow_subselect::value to a FALSE constant Item instead of NULL.

mysql-test/r/subselect.result

@@ -6094,5 +6094,23 @@ SELECT COUNT(f1), f2 IN (SELECT f1 FROM t1 WHERE f2 > 0) AS f4 FROM t2, t1 WHERE
 COUNT(f1)	f4
 0	0
 drop table t1,t2;
+#
+# LP BUG#1002079 Server crashes in Item_singlerow_subselect::val_int with constant table,
+# HAVING, UNION in subquery
+#
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (7),(0);
+CREATE TABLE t2 (b INT);
+EXPLAIN
+SELECT SUM(a) AS f1, a AS f2 FROM (t1, t2) HAVING f2 >= ALL (SELECT 4 UNION SELECT 5) AND f1 = 7;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	system	NULL	NULL	NULL	NULL	0	const row not found
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+SELECT SUM(a) AS f1, a AS f2 FROM (t1, t2) HAVING f2 >= ALL (SELECT 4 UNION SELECT 5) AND f1 = 7;
+f1	f2
+drop table t1,t2;
 # return optimizer switch changed in the beginning of this test
 set optimizer_switch=@subselect_tmp;

mysql-test/r/subselect_no_mat.result

@@ -6093,6 +6093,24 @@ SELECT COUNT(f1), f2 IN (SELECT f1 FROM t1 WHERE f2 > 0) AS f4 FROM t2, t1 WHERE
 COUNT(f1)	f4
 0	0
 drop table t1,t2;
+#
+# LP BUG#1002079 Server crashes in Item_singlerow_subselect::val_int with constant table,
+# HAVING, UNION in subquery
+#
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (7),(0);
+CREATE TABLE t2 (b INT);
+EXPLAIN
+SELECT SUM(a) AS f1, a AS f2 FROM (t1, t2) HAVING f2 >= ALL (SELECT 4 UNION SELECT 5) AND f1 = 7;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	system	NULL	NULL	NULL	NULL	0	const row not found
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+SELECT SUM(a) AS f1, a AS f2 FROM (t1, t2) HAVING f2 >= ALL (SELECT 4 UNION SELECT 5) AND f1 = 7;
+f1	f2
+drop table t1,t2;
 # return optimizer switch changed in the beginning of this test
 set optimizer_switch=@subselect_tmp;
 set optimizer_switch=default;

mysql-test/r/subselect_no_opts.result

@@ -6089,6 +6089,24 @@ SELECT COUNT(f1), f2 IN (SELECT f1 FROM t1 WHERE f2 > 0) AS f4 FROM t2, t1 WHERE
 COUNT(f1)	f4
 0	0
 drop table t1,t2;
+#
+# LP BUG#1002079 Server crashes in Item_singlerow_subselect::val_int with constant table,
+# HAVING, UNION in subquery
+#
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (7),(0);
+CREATE TABLE t2 (b INT);
+EXPLAIN
+SELECT SUM(a) AS f1, a AS f2 FROM (t1, t2) HAVING f2 >= ALL (SELECT 4 UNION SELECT 5) AND f1 = 7;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	system	NULL	NULL	NULL	NULL	0	const row not found
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+SELECT SUM(a) AS f1, a AS f2 FROM (t1, t2) HAVING f2 >= ALL (SELECT 4 UNION SELECT 5) AND f1 = 7;
+f1	f2
+drop table t1,t2;
 # return optimizer switch changed in the beginning of this test
 set optimizer_switch=@subselect_tmp;
 set @optimizer_switch_for_subselect_test=null;

mysql-test/r/subselect_no_scache.result

@@ -6100,6 +6100,24 @@ SELECT COUNT(f1), f2 IN (SELECT f1 FROM t1 WHERE f2 > 0) AS f4 FROM t2, t1 WHERE
 COUNT(f1)	f4
 0	0
 drop table t1,t2;
+#
+# LP BUG#1002079 Server crashes in Item_singlerow_subselect::val_int with constant table,
+# HAVING, UNION in subquery
+#
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (7),(0);
+CREATE TABLE t2 (b INT);
+EXPLAIN
+SELECT SUM(a) AS f1, a AS f2 FROM (t1, t2) HAVING f2 >= ALL (SELECT 4 UNION SELECT 5) AND f1 = 7;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	system	NULL	NULL	NULL	NULL	0	const row not found
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+SELECT SUM(a) AS f1, a AS f2 FROM (t1, t2) HAVING f2 >= ALL (SELECT 4 UNION SELECT 5) AND f1 = 7;
+f1	f2
+drop table t1,t2;
 # return optimizer switch changed in the beginning of this test
 set optimizer_switch=@subselect_tmp;
 set optimizer_switch=default;

mysql-test/r/subselect_no_semijoin.result

@@ -6089,6 +6089,24 @@ SELECT COUNT(f1), f2 IN (SELECT f1 FROM t1 WHERE f2 > 0) AS f4 FROM t2, t1 WHERE
 COUNT(f1)	f4
 0	0
 drop table t1,t2;
+#
+# LP BUG#1002079 Server crashes in Item_singlerow_subselect::val_int with constant table,
+# HAVING, UNION in subquery
+#
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (7),(0);
+CREATE TABLE t2 (b INT);
+EXPLAIN
+SELECT SUM(a) AS f1, a AS f2 FROM (t1, t2) HAVING f2 >= ALL (SELECT 4 UNION SELECT 5) AND f1 = 7;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	PRIMARY	t2	system	NULL	NULL	NULL	NULL	0	const row not found
+1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
+2	SUBQUERY	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+3	UNION	NULL	NULL	NULL	NULL	NULL	NULL	NULL	No tables used
+NULL	UNION RESULT	<union2,3>	ALL	NULL	NULL	NULL	NULL	NULL	
+SELECT SUM(a) AS f1, a AS f2 FROM (t1, t2) HAVING f2 >= ALL (SELECT 4 UNION SELECT 5) AND f1 = 7;
+f1	f2
+drop table t1,t2;
 # return optimizer switch changed in the beginning of this test
 set optimizer_switch=@subselect_tmp;
 set @optimizer_switch_for_subselect_test=null;

mysql-test/t/subselect.test

@@ -5174,6 +5174,21 @@ SELECT COUNT(f1), f2 IN (SELECT f1 FROM t1 WHERE f2 > 0) AS f4 FROM t2, t1 WHERE
 
 drop table t1,t2;
 
+--echo #
+--echo # LP BUG#1002079 Server crashes in Item_singlerow_subselect::val_int with constant table,
+--echo # HAVING, UNION in subquery
+--echo #
+
+CREATE TABLE t1 (a INT);
+INSERT INTO t1 VALUES (7),(0);
+CREATE TABLE t2 (b INT);
+
+EXPLAIN
+SELECT SUM(a) AS f1, a AS f2 FROM (t1, t2) HAVING f2 >= ALL (SELECT 4 UNION SELECT 5) AND f1 = 7;
+
+SELECT SUM(a) AS f1, a AS f2 FROM (t1, t2) HAVING f2 >= ALL (SELECT 4 UNION SELECT 5) AND f1 = 7;
+
+drop table t1,t2;
 
 --echo # return optimizer switch changed in the beginning of this test
 set optimizer_switch=@subselect_tmp;

sql/item_subselect.cc

@@ -892,13 +892,21 @@ void Item_maxmin_subselect::print(String *str, enum_query_type query_type)
 
 void Item_maxmin_subselect::no_rows_in_result()
 {
-  value= 0;
+  value= Item_cache::get_cache(new Item_null());
   null_value= 0;
   was_values= 0;
   make_const();
 }
 
 
+void Item_singlerow_subselect::no_rows_in_result()
+{
+  value= Item_cache::get_cache(new Item_null());
+  reset();
+  make_const();
+}
+
+
 void Item_singlerow_subselect::reset()
 {
   Item_subselect::reset();

sql/item_subselect.h

@@ -267,7 +267,7 @@ class Item_singlerow_subselect :public Item_subselect
   subs_type substype() { return SINGLEROW_SUBS; }
 
   void reset();
-  void no_rows_in_result() { reset(); make_const(); }
+  void no_rows_in_result();
   bool select_transformer(JOIN *join);
   void store(uint i, Item* item);
   double val_real();