MDEV-415: Back-port of the WL task #1393 from the mysql-5.6 code line.

The task adds a more efficient handling of the queries with 
ORDER BY order LIMIT n, such that n is small enough and
no indexes are used for order.

1 files changed, 4 insertions, 2 deletions

diff --git a/sql/sql_update.cc b/sql/sql_update.cc
index f2b6c5c9f92..bf261bffec3 100644
--- a/sql/sql_update.cc
+++ b/sql/sql_update.cc
@@ -498,13 +498,15 @@ int mysql_update(THD *thd,
       uint         length= 0;
       SORT_FIELD  *sortorder;
       ha_rows examined_rows;
+      ha_rows found_rows;
 
       table->sort.io_cache = (IO_CACHE *) my_malloc(sizeof(IO_CACHE),
 						    MYF(MY_FAE | MY_ZEROFILL));
       if (!(sortorder=make_unireg_sortorder(order, &length, NULL)) ||
           (table->sort.found_records= filesort(thd, table, sortorder, length,
-                                               select, limit, 1,
-                                               &examined_rows))
+                                               select, limit,
+                                               true,
+                                               &examined_rows, &found_rows))
           == HA_POS_ERROR)
       {
 	goto err;