Bug #55615 and bug #55564

An user assignment variable expression that's 
evaluated in a logical expression context 
(Item::val_bool()) can be pre-calculated in a 
temporary table for GROUP BY.
However when the expression value is used after the
temp table creation it was re-evaluated instead of
being read from the temp table due to a missing 
val_bool_result() method.
Fixed by implementing the method.

mysql-test/r/user_var.result

@@ -430,4 +430,21 @@ CREATE TRIGGER t_after_insert AFTER INSERT ON t1 FOR EACH ROW SET @bug42188 = 10
 INSERT INTO t1 VALUES (1);
 INSERT INTO t1 VALUES (1);
 DROP TABLE t1;
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES (0),(0);
+# BUG#55615 : should not crash
+SELECT (@a:=(SELECT @a:=1 FROM t1 LIMIT 1)) AND COUNT(1) FROM t1 GROUP BY @a;
+(@a:=(SELECT @a:=1 FROM t1 LIMIT 1)) AND COUNT(1)
+1
+1
+# BUG#55564 : should not crash
+SELECT IF(
+@v:=LEAST((SELECT 1 FROM t1 t2 LEFT JOIN t1 ON (@v) GROUP BY t1.a), a),
+count(*), 1) 
+FROM t1 GROUP BY a LIMIT 1;
+IF(
+@v:=LEAST((SELECT 1 FROM t1 t2 LEFT JOIN t1 ON (@v) GROUP BY t1.a), a),
+count(*), 1)
+1
+DROP TABLE t1;
 End of 5.1 tests

mysql-test/t/user_var.test

@@ -328,4 +328,22 @@ INSERT INTO t1 VALUES (1);
 INSERT INTO t1 VALUES (1);
 DROP TABLE t1;
 
+#
+# Bug #55615: debug assertion after using variable in assignment and
+# referred to
+# Bug #55564: crash with user variables, assignments, joins...
+#
+
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES (0),(0);
+--echo # BUG#55615 : should not crash
+SELECT (@a:=(SELECT @a:=1 FROM t1 LIMIT 1)) AND COUNT(1) FROM t1 GROUP BY @a;
+--echo # BUG#55564 : should not crash
+SELECT IF(
+  @v:=LEAST((SELECT 1 FROM t1 t2 LEFT JOIN t1 ON (@v) GROUP BY t1.a), a),
+  count(*), 1) 
+FROM t1 GROUP BY a LIMIT 1;
+
+DROP TABLE t1;
+
 --echo End of 5.1 tests

sql/item_func.cc

@@ -4263,6 +4263,14 @@ longlong Item_func_set_user_var::val_int_result()
   return entry->val_int(&null_value);
 }
 
+bool Item_func_set_user_var::val_bool_result()
+{
+  DBUG_ASSERT(fixed == 1);
+  check(TRUE);
+  update();					// Store expression
+  return entry->val_int(&null_value) != 0;
+}
+
 String *Item_func_set_user_var::str_result(String *str)
 {
   DBUG_ASSERT(fixed == 1);

sql/item_func.h

@@ -1353,6 +1353,7 @@ class Item_func_set_user_var :public Item_func
   my_decimal *val_decimal(my_decimal *);
   double val_result();
   longlong val_int_result();
+  bool val_bool_result();
   String *str_result(String *str);
   my_decimal *val_decimal_result(my_decimal *);
   bool is_null_result();