vadvs (vadvs) wrote in changelog,
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[livejournal] r23541: LJSUP-14799: Add "use index" hint to sql...

Committer: vad
LJSUP-14799: Add "use index" hint to sql query get subscriptions in a appropriate time
U   trunk/cgi-bin/LJ/Event.pm
Modified: trunk/cgi-bin/LJ/Event.pm
===================================================================
--- trunk/cgi-bin/LJ/Event.pm	2013-01-14 15:54:37 UTC (rev 23540)
+++ trunk/cgi-bin/LJ/Event.pm	2013-01-15 07:30:18 UTC (rev 23541)
@@ -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)
             });

Tags: livejournal, pm, vad, vadvs
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