| From: | Michael Paquier <michael(at)paquier(dot)xyz> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com>, Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(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 02:27:43 |
| Message-ID: | 20180328022743.GH1105@paquier.xyz |
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| Lists: | pgsql-hackers |
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.
--
Michael
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