MDEV-27406 Index on a HEAP table retains DESC attribute despite being hash

just like in SHOW KEYS, suppress DESC in SHOW CREATE if not HA_READ_ORDER

mysql-test/suite/heap/heap_hash.result

-drop table if exists t1,t2;
 create table t1 (a int not null,b int not null, primary key using HASH (a)) engine=heap comment="testing heaps" avg_row_length=100 min_rows=1 max_rows=100;
 insert into t1 values(1,1),(2,2),(3,3),(4,4);
 delete from t1 where a=1 or a=0;
@@ -467,4 +466,23 @@ SELECT * FROM t1 WHERE c1='bar2';
 c1
 bar2
 DROP TABLE t1;
-End of 5.5 tests
+#
+# End of 5.5 tests
+#
+#
+# MDEV-27406 Index on a HEAP table retains DESC attribute despite being hash
+#
+create table t1 (a int, key(a desc)) engine=memory;
+show index from t1;
+Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment	Ignored
+t1	1	a	1	a	NULL	0	NULL	NULL	YES	HASH			NO
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` int(11) DEFAULT NULL,
+  KEY `a` (`a`)
+) ENGINE=MEMORY DEFAULT CHARSET=latin1
+drop table t1;
+#
+# End of 10.8 tests
+#

mysql-test/suite/heap/heap_hash.test

@@ -2,10 +2,6 @@
 # Test of heap tables.
 #
 
---disable_warnings
-drop table if exists t1,t2;
---enable_warnings
-
 create table t1 (a int not null,b int not null, primary key using HASH (a)) engine=heap comment="testing heaps" avg_row_length=100 min_rows=1 max_rows=100;
 insert into t1 values(1,1),(2,2),(3,3),(4,4);
 delete from t1 where a=1 or a=0;
@@ -346,4 +342,18 @@ explain SELECT * FROM t1 WHERE c1='bar2';
 SELECT * FROM t1 WHERE c1='bar2';
 DROP TABLE t1;
 
---echo End of 5.5 tests
+--echo #
+--echo # End of 5.5 tests
+--echo #
+
+--echo #
+--echo # MDEV-27406 Index on a HEAP table retains DESC attribute despite being hash
+--echo #
+create table t1 (a int, key(a desc)) engine=memory;
+show index from t1;
+show create table t1;
+drop table t1;
+
+--echo #
+--echo # End of 10.8 tests
+--echo #

sql/sql_show.cc

@@ -2369,7 +2369,8 @@ int show_create_table_ex(THD *thd, TABLE_LIST *table_list,
         packet->append_parenthesized((long) key_part->length /
                                       key_part->field->charset()->mbmaxlen);
       }
-      if (key_part->key_part_flag & HA_REVERSE_SORT)
+      if (table->file->index_flags(i, j, 0) & HA_READ_ORDER &&
+          key_part->key_part_flag & HA_REVERSE_SORT) /* same in SHOW KEYS */
         packet->append(STRING_WITH_LEN(" DESC"));
     }