public inbox for [email protected]
help / color / mirror / Atom feedFrom: Jeff Janes <[email protected]>
To: Charles Nadeau <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: Very poor read performance, query independent
Date: Wed, 12 Jul 2017 15:27:27 -0700
Message-ID: <CAMkU=1xU+GVfK5OmdPcvK9TjzPfn7E3BD5ugYn8iapg8OFy7Lw@mail.gmail.com> (raw)
In-Reply-To: <CADFyZw4RTBtWUeo-6Q_GcsqawkF+gSe4JGEpASUE6msiu=01xA@mail.gmail.com>
References: <CADFyZw7aGoD0AaStxdyHByR5Qta=M5wx0v=iptKLhPUp+EOKvA@mail.gmail.com>
<CAMkU=1z92pimpoDV1oTpd4AvSHS0CrLzQDFSxw1Z5cpmmjEOkw@mail.gmail.com>
<CADFyZw7Am=mv-6RXOr_C2oxEhPyKjnbvFgaEPq+-aKw+j9oDrw@mail.gmail.com>
<CAMkU=1zD=SNFF=U-HtRHcu2dAdqyorD6o_UCQoYHuoh-gcs_uA@mail.gmail.com>
<CADFyZw4RTBtWUeo-6Q_GcsqawkF+gSe4JGEpASUE6msiu=01xA@mail.gmail.com>
List-Unsubscribe: <mailto:[email protected]?body=unsub%20pgsql-performance>
On Wed, Jul 12, 2017 at 3:04 AM, Charles Nadeau <[email protected]>
wrote:
> Jeff,
>
> Here are the 2 EXPLAINs for one of my simplest query:
>
It looks like dstexterne and flowcompact are both views over flow. Can you
share the definition of those views?
I think the iowait > 12.5% is due to the parallel query execution. But
then the question is, why is it only 25% when you have 10 fold parallelism?
It certainly looks like you are doing more than 4MB/s there, so maybe
something is wrong with the instrumentation, or how you are interpreting
it.
Although it is still less than perhaps it could do. To put a baseline on
what you can expect out of parallel seq scans, can you do something like:
explain (analyze, buffers) select avg(doctets) from flow;
Cheers,
Jeff
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: [email protected]
Cc: [email protected], [email protected]
Subject: Re: Very poor read performance, query independent
In-Reply-To: <CAMkU=1xU+GVfK5OmdPcvK9TjzPfn7E3BD5ugYn8iapg8OFy7Lw@mail.gmail.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox