From: | Brad Nicholson <bnichols(at)ca(dot)afilias(dot)info> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Russell Smith <mr-russ(at)pws(dot)com(dot)au>, Jean-David Beyer <jeandavid8(at)verizon(dot)net>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Curious about dead rows. |
Date: | 2007-11-16 15:56:48 |
Message-ID: | 1195228608.8966.364.camel@bnicholson-desktop |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-performance |
On Wed, 2007-11-14 at 17:46 -0500, Tom Lane wrote:
> Russell Smith <mr-russ(at)pws(dot)com(dot)au> writes:
> > It is possible that analyze is not getting the number of dead rows right?
>
> Hah, I think you are on to something. ANALYZE is telling the truth
> about how many "dead" rows it saw, but its notion of "dead" is "not good
> according to SnapshotNow". Thus, rows inserted by a not-yet-committed
> transaction would be counted as dead. So if these are background
> auto-analyzes being done in parallel with inserting transactions that
> run for awhile, seeing a few not-yet-committed rows would be
> unsurprising.
>
> I wonder if that is worth fixing? I'm not especially concerned about
> the cosmetic aspect of it, but if we mistakenly launch an autovacuum
> on the strength of an inflated estimate of dead rows, that could be
> costly.
Sounds to me like that could result in autovacuum kicking off while
doing large data loads. This sounds suspiciously like problem someone
on -novice was having - tripping over a windows autovac bug while doing
a data load
http://archives.postgresql.org/pgsql-novice/2007-11/msg00025.php
--
Brad Nicholson 416-673-4106
Database Administrator, Afilias Canada Corp.
From | Date | Subject | |
---|---|---|---|
Next Message | Jonah H. Harris | 2007-11-16 16:06:11 | Re: PostgreSQL vs MySQL, and FreeBSD |
Previous Message | Dave Dutcher | 2007-11-16 15:56:28 | Re: PostgreSQL vs MySQL, and FreeBSD |