| From: | Petr Jelinek <petr(at)2ndquadrant(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de> |
| Cc: | Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru>, PostgreSQL Developers <pgsql-hackers(at)postgreSQL(dot)org> |
| Subject: | Re: Applying logical replication changes by more than one process |
| Date: | 2016-03-21 13:30:19 |
| Message-ID: | 56EFF76B.6060700@2ndquadrant.com |
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| Lists: | pgsql-hackers |
On 21/03/16 14:25, Andres Freund wrote:
> On 2016-03-21 14:18:27 +0100, Petr Jelinek wrote:
>> On 21/03/16 14:15, Andres Freund wrote:
>>>> Only when the origin is actually setup for the current session. You
>>>> need
>>>> to call the replorigin_advance yourself from your apply code.
>>>
>>> That's problematic from a durability POV.
>>>
>>
>> Huh? How come?
>
> If you use the session mechanism the replication progress is synced with
> the apply process, even if there are crashes. Crash recovery updates the
> progress. There's no such interlock with apply otherwise, and I don't
> see how you can build one with reasonable effort.
>
Ah you mean because with wal_log=true the origin advance is in different
WAL record than commit? OK yeah you might be one transaction behind
then, true.
--
Petr Jelinek http://www.2ndQuadrant.com/
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