| From: | Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com> |
|---|---|
| To: | Michael Paquier <michael(at)paquier(dot)xyz> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Changing WAL Header to reduce contention during ReserveXLogInsertLocation() |
| Date: | 2018-03-28 03:43:19 |
| Message-ID: | CAA8=A781Zrwgddhf5i3OP-5FXijY4Uc9w3NoYHpVSaQk-Zj4HA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Mar 28, 2018 at 12:57 PM, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> On Tue, Mar 27, 2018 at 10:09:59PM -0400, Robert Haas wrote:
>>> I have to agree with Tom here. If you force pg_rewind to replay more
>>> WAL records from a checkpoint older than the checkpoint prior to where
>>> WAL has forked at promotion then you have a risk of losing data.
>>
>> Oh! I see now. Good point.
>
> Something that would address the issue would be to enforce a segment
> switch after each checkpoint, but that's a high price to pay on mostly
> idle systems with large WAL segments, which is not appealing either, and
> this even if the checkpoint skip logic has been fixed in v10 with the
> concept of "important" WAL records.
If the system is mostly idle would it really matter that much?
cheers
andrew
--
Andrew Dunstan https://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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