What is syslog:duration reporting ... ?

From: "Marc G(dot) Fournier" <scrappy(at)postgresql(dot)org>
To: pgsql-admin(at)postgresql(dot)org
Subject: What is syslog:duration reporting ... ?
Date: 2005-08-25 18:28:21
Message-ID: 20050825152428.T1044@ganymede.hub.org
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'k, I've been wracking my brains over this today, and I'm either
mis-understanding what is being reported *or* its reporting wrong ...

According to syslog:

LOG: duration: 4107.987 ms statement: UPDATE session SET hit_time=now() WHERE md5='8b8e7b7ff9b1b2ed5fc60218ced28d00';

But, if I do an EXPLAIN ANALYZE:

# explain analyze UPDATE session SET hit_time=now() WHERE md5='702c6cb20d5eb254c3feb2991e7e5e31';
QUERY PLAN
----------------------------------------------------------------------------------------------------------------------------
Index Scan using session_md5_key on "session" (cost=0.00..6.01 rows=1 width=93) (actual time=0.060..0.060 rows=0 loops=1)
Index Cond: (md5 = '702c6cb20d5eb254c3feb2991e7e5e31'::bpchar)
Total runtime: 0.171 ms
(3 rows)

And it doesn't matter what value I put for md5, I still get <1ms ...

I could see some variations, but almost 4000x slower to *really* run the
query vs an explain analyze?

This is with 7.4.2 ...

----
Marc G. Fournier Hub.Org Networking Services (http://www.hub.org)
Email: scrappy(at)hub(dot)org Yahoo!: yscrappy ICQ: 7615664

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