Re: Logical replication existing data copy

On 06/03/17 23:40, Erik Rijkers wrote:
> On 2017-03-06 16:10, Erik Rijkers wrote:
>> On 2017-03-06 11:27, Petr Jelinek wrote:
>>> Hi,
>>>
>>> updated and rebased version of the patch attached.
>>>
>>
>> I compiled with /only/ this one latest patch:
>> 0001-Logical-replication-support-for-initial-data-copy-v6.patch
>>
>> Is that correct, or are other patches still needed on top, or underneath?
>>
>
> TWIMC, I'll answer my own question: the correct patchset seems to be
> these six:
>
> 0001-Reserve-global-xmin-for-create-slot-snasphot-export.patch
> 0002-Don-t-use-on-disk-snapshots-for-snapshot-export-in-l.patch
> 0003-Prevent-snapshot-builder-xmin-from-going-backwards.patch
> 0004-Fix-xl_running_xacts-usage-in-snapshot-builder.patch
> 0005-Skip-unnecessary-snapshot-builds.patch
> 0001-Logical-replication-support-for-initial-data-copy-v6.patch
>

Yes the 0004 and 0005 improve performance of snapshot creation
considerably. They're also the reason we uncovered all the snapbuilder
bugs now. Before the performance optimization it was very unlikely for
some of the race conditions to happen as the snapshot would just not be
built until there was less concurrent traffic on the server.

--
Petr Jelinek http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services