Re: Remove secondary checkpoint

From: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Remove secondary checkpoint
Date: 2017-11-07 23:17:56
Message-ID: CAB7nPqTeke3U2kcD8dABa9PgyH75-8GuVFR5NG75qgsQogEyPg@mail.gmail.com
Views: Raw Message | Whole Thread | Download mbox
Thread:
Lists: pgsql-hackers

On Wed, Nov 8, 2017 at 2:23 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On 31 October 2017 at 12:01, Michael Paquier <michael(dot)paquier(at)gmail(dot)com> wrote:
>> While the mention about a manual checkpoint happening after a timed
>> one will cause a full range of WAL segments to be recycled, it is not
>> actually true that segments of the prior's prior checkpoint are not
>> needed, because with your patch the segments of the prior checkpoint
>> are getting recycled. So it seems to me that based on that the formula
>> ought to use 1.0 instead of 2.0...
>
> I think the argument in the comment is right, in that
> CheckPointDistanceEstimate is better if we use multiple checkpoint
> cycles.

Yes, the theory behind is correct. No argument behind that.

> But the implementation of that is bogus and multiplying by 2.0
> wouldn't make it better if CheckPointDistanceEstimate is wrong.

Yes, this is wrong. My apologies if my words looked confusing. By
reading your message I can see that our thoughts are on the same page.
--
Michael

In response to

Browse pgsql-hackers by date

  From Date Subject
Next Message Michael Paquier 2017-11-07 23:21:49 Re: Exclude pg_internal.init from base backup
Previous Message Peter Geoghegan 2017-11-07 22:50:38 Re: Small improvement to compactify_tuples