Re: Database performs massive reads when I'm doing writes.

And... it was a rookie mistake.
In answering the last question I once again looked at the database and realized there was an index missing!
Swear it has been there before (and I should have double-checked sooner).
Added the index and now we're moving right along.

Thanks for all leads everyone sent me.
Learned a lot about Postgresql today.
--Ray

----- Original Message -----

> From: "Ray Cote" <rgacote(at)appropriatesolutions(dot)com>
> To: "Jeff Janes" <jeff(dot)janes(at)gmail(dot)com>
> Cc: pgsql-general(at)postgresql(dot)org
> Sent: Thursday, June 6, 2013 5:12:51 PM
> Subject: Re: [GENERAL] Database performs massive reads when I'm doing
> writes.

> It is Postmaster itself:
> 11068 - 315.9M 136K 0K 85% postmaster
> 11000 - 56808K 8K 0K 15% postmaster
> 11003 - 0K 80K 0K 0% postmaster
> 11004 - 0K 24K 0K 0% postmaster
> 11067 - 0K 0K 0K 0% load_rets.py

> The above are the atop lines for just postmaster. This is a 10s
> snapshot so you can see lots of read activity.
> The load_rets.py task is the Python script loading the database.

> --Ray

> ----- Original Message -----

> > From: "Jeff Janes" <jeff(dot)janes(at)gmail(dot)com>
>
> > To: "Ray Cote" <rgacote(at)appropriatesolutions(dot)com>
>
> > Cc: pgsql-general(at)postgresql(dot)org
>
> > Sent: Thursday, June 6, 2013 4:05:28 PM
>
> > Subject: Re: [GENERAL] Database performs massive reads when I'm
> > doing
> > writes.
>

> > On Thu, Jun 6, 2013 at 9:53 AM, Ray Cote <
> > rgacote(at)appropriatesolutions(dot)com > wrote:
>

> > > Hello:
> >
>

> > > I have a PostgreSQL 9.0.3 database that has suddenly started
> > > exhibiting odd read behavior.
> >
>

> > > The version number is:
> >
>
> > > "PostgreSQL 9.0.3 on x86_64-unknown-linux-gnu, compiled by GCC
> > > gcc
> > > (GCC) 4.1.2 20080704 (Red Hat 4.1.2-50), 64-bit"
> >
>
> > > This was compiled from source about a year ago and has been
> > > running
> > > just fine.
> >
>
> > > The database feeds a very low-volume web site (a few hits per
> > > minute).
> >
>

> > > Starting a few days ago we started to see a strange behavior
> > > where
> > > writing to the database causes massive read operations.
> >
>
> > > For example, I have a table that needs to be updated every night
> > > (about 20,000 rows).
> >
>
> > > Using Django ORM, we update them one item at a time.
> >
>
> > > Usually the overall process takes a few minutes; it is now taking
> > > hours (like over 15 hours).
> >
>

> > > Running atop, we're seeing Read Disk values in the range of
> > > 147.2M/10s and Write Disk values in the range of 16K/10s.
> >
>
> > > Together, the Disk throughput is in the high 90% and frequently
> > > hits
> > > 100%.
> >
>

> > Which specific processes are using the disk? (on my atop, if I hit
> > 'c' it will change mode to show me the entire so-called "command
> > line", which will let you know if the culprit is a vacuum worker,
> > the checkpointer, or someone else).
>

> > Cheers,
>

> > Jeff
>
> --

> Ray Cote, President Appropriate Solutions, Inc.
> We Build Software
> www.AppropriateSolutions.com 603.924.6079

--

Ray Cote, President Appropriate Solutions, Inc.
We Build Software
www.AppropriateSolutions.com 603.924.6079