[livejournal] r23562: LJSUP-14875: [internal] add "use index" ...

U   trunk/cgi-bin/LJ/Event.pm

Modified: trunk/cgi-bin/LJ/Event.pm
===================================================================
--- trunk/cgi-bin/LJ/Event.pm	2013-01-18 09:19:36 UTC (rev 23561)
+++ trunk/cgi-bin/LJ/Event.pm	2013-01-18 12:52:37 UTC (rev 23562)
@@ -689,11 +689,14 @@
             # FIXME: journals are only on one cluster! split jidlist based on cluster
             my $jidlist = join(",", @wildcards_from);
 
+            ## Strictly specify USE INDEX(PRIMARY) hint.
+            ## Otherwise mysql query planner is acting out and query takes inexcusable amount of time.
             my $sth = $udbh->prepare(qq{
                 SELECT
                     userid, subid, is_dirty, journalid, etypeid,
                     arg1, arg2, ntypeid, createtime, expiretime, flags
                 FROM subs
+                USE INDEX(PRIMARY)
                 WHERE etypeid=? AND journalid=0 $and_enabled
                     AND userid IN ($jidlist)
             });