BUG#12915: Added single-table UPDATE/DELTE ... ORDER BY ... LIMIT

optimization: now can use index to find records to update/delete
when there is no WHERE clause.

1 files changed, 29 insertions, 0 deletions

diff --git a/mysql-test/t/update.test b/mysql-test/t/update.test
index 84e9ced2017..a37655b15fe 100644
--- a/mysql-test/t/update.test
+++ b/mysql-test/t/update.test
@@ -227,4 +227,33 @@ select DATABASE();
 delete from t1 where count(*)=1;
 drop table t1;
 
+# BUG#12915: Optimize "DELETE|UPDATE ... ORDER BY ... LIMIT n" to use an index
+create table t1 ( a int, index (a) );
+insert into t1 values (0),(0),(0),(0),(0),(0),(0),(0);
+
+flush status;
+select a from t1 order by a limit 1;
+show status like 'handler_read%';
+
+flush status;
+update t1 set a=unix_timestamp() order by a limit 1;
+show status like 'handler_read%';
+
+flush status;
+delete from t1 order by a limit 1;
+show status like 'handler_read%';
+
+flush status;
+delete from t1 order by a desc limit 1;
+show status like 'handler_read%';
+
+alter table t1 disable keys;
+
+flush status;
+delete from t1 order by a limit 1;
+show status like 'handler_read%';
+
+select count(*) from t1;
+
+drop table t1;
 # End of 4.1 tests