From: | Andres Freund <andres(at)2ndquadrant(dot)com> |
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To: | Kevin Grittner <kgrittn(at)ymail(dot)com> |
Cc: | Alexander Korotkov <aekorotkov(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: pg_dump with both --serializable-deferrable and -j |
Date: | 2015-01-28 21:35:40 |
Message-ID: | 20150128213540.GF13446@awork2.anarazel.de |
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Lists: | pgsql-hackers |
On 2015-01-28 15:32:15 +0000, Kevin Grittner wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> > ISTM that the check is just overzelous and/or needs to be moved into
> > ImportSnapshot(). There it then could be made to check if the exporting
> > xact was also deferrable.
>
> That would be great if ImportSnapshot had access to that
> information; I don't see it, though. Having pg_dump use repeatable
> read transactions for the processes that import the snapshot would
> work fine, as long as they are reading a snapshot which was
> captured by a serializable read only deferrable transaction.
Then add that information? The disk format for snapshot isn't persistent
across restarts, so we can just extend it.
I really don't like adding hacks like using a lower serializability
level than what's actually requested just because it happens to be
easier. Even if it's just in some backend.
Greetings,
Andres Freund
--
Andres Freund http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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