| From: | Craig Ringer <craig(at)2ndquadrant(dot)com> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Petr Jelinek <petr(at)2ndquadrant(dot)com> |
| Subject: | Re: Potential hot-standby bug around xacts committed but in xl_running_xacts |
| Date: | 2017-05-02 06:24:49 |
| Message-ID: | CAMsr+YEjygnXYCpJeWO4xQVHg0qWoKTPaQiAqto4Xy=odAK5xw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 2 May 2017 at 13:12, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> What I suggest is that with logical decoding in mind we do this
> 1. Inject a new record XLOG_SNAPSHOT_START at the start of
> LogStandbySnapshot(). We start logical decoding from there.
> 2. Record any transactions that end
> 3. Now the full XLOG_RUNNING_XACTS record arrives. We apply all xacts
> that are seen as running, minus any ended between 1 and 3
>
> This avoids the problems for the race but without holding locks while
> we log XLOG_RUNNING_XACTS, something that was considered painful for
> Hot Standby.
Sounds like a sensible solution to me. It avoids the need for a rather
undesirable interlock between xlog and shmem commit.
--
Craig Ringer http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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