[Gforge-commits] gforge/cronjobs massmail.php,1.14,1.15

[tom]

Update of /cvsroot/gforge/gforge/cronjobs
In directory db.perdue.net:/tmp/cvs-serv4506

Modified Files:
        massmail.php 
Log Message:
Added a comment about the use of DISTINCT in this query

Index: massmail.php
===================================================================
RCS file: /cvsroot/gforge/gforge/cronjobs/massmail.php,v
retrieving revision 1.14
retrieving revision 1.15
diff -u -d -r1.14 -r1.15
--- massmail.php        20 Jul 2004 18:54:09 -0000      1.14
+++ massmail.php        21 Oct 2004 18:54:20 -0000      1.15
@@ -103,6 +103,11 @@
 
 //$err .= "Got mail to send: ".$subj."\n";
 
+// While using DISTINCT is usually evil (because you're fetching rows
+// and then discarding them), in this case it's actually good.  Running 
+// EXPLAIN ANALYZE on this query on my GForge server (1000 users, 380 
projects) 
+// shows that it takes about 25 ms.  But after rewriting it to use an 
uncorrelated subquery,
+// it takes around 650 ms.  So I think we'll leave it the way it is :-)
 $sql = "SELECT DISTINCT 
users.user_id,users.user_name,users.realname,users.email,users.confirm_hash
        FROM $table_mapping[$type]
        WHERE users.user_id>".db_result($mail_res, 0, 'last_userid')."