| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | "anarazel(at)anarazel(dot)de" <andres(at)anarazel(dot)de> |
| Cc: | Andres Freund <andres(at)2ndquadrant(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Peter Geoghegan <peter(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: logical decoding - GetOldestXmin |
| Date: | 2012-12-19 00:56:18 |
| Message-ID: | CA+TgmoZFBgE8FMwONw9GY=s5CnFNksXCnfkWet2oi_XYMqG-rw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Dec 18, 2012 at 5:25 PM, anarazel(at)anarazel(dot)de
<andres(at)anarazel(dot)de> wrote:
> The problem is that at the time GetSnapshotData returns the xmin horizon might have gone upwards and tuples required for decoding might get removed by other backends. That needs to be prevented while holding the procarray lock exclusively.
Well, for the ordinary use of GetSnapshotData(), that doesn't matter,
because GetSnapshotData() also updates proc->xmin. If you're trying
to store a different value in that field then of course it matters.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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