Merge

mysql-test/r/update.result

@@ -603,3 +603,30 @@ Variable_name	Value
 Handler_update	5
 ROLLBACK;
 DROP TABLE t1, t2;
+#
+# MDEV-4410: update does not want to use a covering index, but select uses it.
+#
+create table t2(a int);
+insert into t2 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+create table t1 (key1 int, col1 int, key(key1));
+insert into t1
+select A.a + 10 * B.a + 100 * C.a, 1234 from t2 A, t2 B, t2 C;
+# This must not have "Using filesort":
+explain 
+update t1 set key1=key1+1 where key1 between 10 and 110 order by key1 limit 2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	range	key1	key1	5	NULL	100	Using where; Using buffer
+flush status;
+update t1 set key1=key1+1 where key1 between 10 and 110 order by key1 limit 2;
+show status like 'Handler_read%';
+Variable_name	Value
+Handler_read_first	0
+Handler_read_key	1
+Handler_read_last	0
+Handler_read_next	1
+Handler_read_prev	0
+Handler_read_rnd	2
+Handler_read_rnd_deleted	0
+Handler_read_rnd_next	0
+drop table t1, t2;
+# End of MariaDB 10.0 tests

mysql-test/t/update.test

@@ -544,3 +544,25 @@ SHOW STATUS LIKE 'HANDLER_UPDATE';
 ROLLBACK;
 DROP TABLE t1, t2;
 
+--echo #
+--echo # MDEV-4410: update does not want to use a covering index, but select uses it.
+--echo #
+create table t2(a int);
+insert into t2 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+
+create table t1 (key1 int, col1 int, key(key1));
+insert into t1
+select A.a + 10 * B.a + 100 * C.a, 1234 from t2 A, t2 B, t2 C;
+
+--echo # This must not have "Using filesort":
+explain 
+update t1 set key1=key1+1 where key1 between 10 and 110 order by key1 limit 2;
+
+flush status;
+update t1 set key1=key1+1 where key1 between 10 and 110 order by key1 limit 2;
+# Handler_read_next should be 1 (due to LIMIT), not 100:
+show status like 'Handler_read%';
+
+drop table t1, t2;
+
+--echo # End of MariaDB 10.0 tests

sql/sql_update.cc

@@ -502,7 +502,7 @@ int mysql_update(THD *thd,
   if (used_key_is_modified || order ||
       partition_key_modified(table, table->write_set))
   {
-    if (order && (need_sort || used_key_is_modified))
+    if (order && need_sort)
       query_plan.using_filesort= true;
     else
       query_plan.using_io_buffer= true;