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.

1 files changed, 18 insertions, 0 deletions

diff --git a/mysql-test/r/subselect_no_scache.result b/mysql-test/r/subselect_no_scache.result
index 47764802df2..b8fb9cad049 100644
--- a/mysql-test/r/subselect_no_scache.result
+++ b/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;