Bug #55472: Assertion failed in heap_rfirst function of hp_rfirst.c on

            DELETE statement

Single-table delete ordered by a field that has a hash-type index
may cause an assertion failure or a crash.

An optimization added by the fix for the bug 36569 forced the
optimizer to use ORDER BY-compatible indices when applicable.

However, the existence of unsorted indices (HASH index algorithm
for some engines such as MEMORY/HEAP, NDB) was ignored.

The test_if_order_by_key function has been modified to skip
unsorted indices.

mysql-test/r/heap_hash.result

@@ -382,3 +382,14 @@ INSERT INTO t1 VALUES('A ', 'A ');
 ERROR 23000: Duplicate entry 'A -A ' for key 'key1'
 DROP TABLE t1;
 End of 5.0 tests
+#
+# Bug #55472: Assertion failed in heap_rfirst function of hp_rfirst.c
+#             on DELETE statement
+#
+CREATE TABLE t1 (col_int_nokey INT,
+col_int_key INT,
+INDEX(col_int_key) USING HASH) ENGINE = HEAP;
+INSERT INTO t1 (col_int_nokey, col_int_key) VALUES (3, 0), (4, 0), (3, 1);
+DELETE FROM t1 WHERE col_int_nokey = 5 ORDER BY col_int_key LIMIT 2;
+DROP TABLE t1;
+End of 5.5 tests

mysql-test/t/heap_hash.test

@@ -284,3 +284,20 @@ INSERT INTO t1 VALUES('A ', 'A ');
 DROP TABLE t1;
 
 --echo End of 5.0 tests
+
+--echo #
+--echo # Bug #55472: Assertion failed in heap_rfirst function of hp_rfirst.c
+--echo #             on DELETE statement
+--echo #
+
+CREATE TABLE t1 (col_int_nokey INT,
+                 col_int_key INT,
+		 INDEX(col_int_key) USING HASH) ENGINE = HEAP;
+INSERT INTO t1 (col_int_nokey, col_int_key) VALUES (3, 0), (4, 0), (3, 1);
+
+DELETE FROM t1 WHERE col_int_nokey = 5 ORDER BY col_int_key LIMIT 2;
+
+DROP TABLE t1;
+
+--echo End of 5.5 tests
+

sql/sql_select.cc

@@ -13244,7 +13244,7 @@ static int test_if_order_by_key(ORDER *order, TABLE *table, uint idx,
         DBUG_RETURN(0);
     }
 
-    if (key_part->field != field)
+    if (key_part->field != field || !field->part_of_sortkey.is_set(idx))
       DBUG_RETURN(0);
 
     /* set flag to 1 if we can use read-next on key, else to -1 */