Re: Changing WAL Header to reduce contention during ReserveXLogInsertLocation()

On Wed, Mar 28, 2018 at 12:57 PM, Michael Paquier <michael@paquier.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
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