MDEV-27683 EXCHANGE PARTITION allows different index direction, but causes further errors

mysql-test/main/partition_exchange.result

@@ -1239,3 +1239,14 @@ DROP TABLE t1, t2;
 #
 # End of 10.3 tests
 #
+#
+# MDEV-27683 EXCHANGE PARTITION allows different index direction, but causes further errors
+#
+CREATE TABLE t1 (a INT, KEY(a DESC)) PARTITION BY KEY(a) PARTITIONS 4;
+CREATE TABLE t2 (a INT, KEY(a));
+ALTER TABLE t1 EXCHANGE PARTITION p0 WITH TABLE t2;
+ERROR HY000: Tables have different definitions
+DROP TABLE t1, t2;
+#
+# End of 10.8 tests
+#

mysql-test/main/partition_exchange.test

@@ -535,3 +535,16 @@ DROP TABLE t1, t2;
 --echo #
 --echo # End of 10.3 tests
 --echo #
+
+--echo #
+--echo # MDEV-27683 EXCHANGE PARTITION allows different index direction, but causes further errors
+--echo #
+CREATE TABLE t1 (a INT, KEY(a DESC)) PARTITION BY KEY(a) PARTITIONS 4;
+CREATE TABLE t2 (a INT, KEY(a));
+--error ER_TABLES_DIFFERENT_METADATA
+ALTER TABLE t1 EXCHANGE PARTITION p0 WITH TABLE t2;
+DROP TABLE t1, t2;
+
+--echo #
+--echo # End of 10.8 tests
+--echo #

sql/sql_table.cc

@@ -7147,7 +7147,8 @@ bool mysql_compare_tables(TABLE *table, Alter_info *alter_info,
         are equal. Comparing field numbers is sufficient.
       */
       if ((table_part->length != new_part->length) ||
-          (table_part->fieldnr - 1 != new_part->fieldnr))
+          (table_part->fieldnr - 1 != new_part->fieldnr) ||
+          ((table_part->key_part_flag ^ new_part->key_part_flag) & HA_REVERSE_SORT))
         DBUG_RETURN(false);
     }
   }