Re: Load Distributed Checkpoints, take 3 - Mailing list pgsql-patches

From Tom Lane
Subject Re: Load Distributed Checkpoints, take 3
Date
Msg-id 25194.1182880676@sss.pgh.pa.us
Whole thread Raw
In response to Re: Load Distributed Checkpoints, take 3  (Heikki Linnakangas <heikki@enterprisedb.com>)
Responses Re: Load Distributed Checkpoints, take 3  (Greg Smith <gsmith@gregsmith.com>)
List pgsql-patches
Heikki Linnakangas <heikki@enterprisedb.com> writes:
> To recap, the sequence is:

> 1. COPY FROM
> 2. checkpoint
> 3. VACUUM

> Now you have buffer cache full of dirty buffers with usage_count=1,

Well, it won't be very full, because VACUUM works in a limited number of
buffers (and did even before the BufferAccessStrategy patch).

I have no doubt that there are scenarios such as you are thinking about,
but it definitely seems like a corner case that doesn't justify keeping
the all-buffers scan.  That scan is costing us extra I/O in ordinary
non-corner cases, so it's not free to keep it.

            regards, tom lane

pgsql-patches by date:

Previous
From: Heikki Linnakangas
Date:
Subject: Re: Load Distributed Checkpoints, take 3
Next
From: Greg Smith
Date:
Subject: Re: Load Distributed Checkpoints, take 3