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Re: logical decoding - GetOldestXmin

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: "anarazel@anarazel.de" <andres@anarazel.de>
Cc: Andres Freund <andres@2ndquadrant.com>, Simon Riggs <simon@2ndquadrant.com>, Peter Geoghegan <peter@2ndquadrant.com>, pgsql-hackers@postgresql.org
Date: 2012-12-19T00:56:18Z
Lists: pgsql-hackers 
On Tue, Dec 18, 2012 at 5:25 PM, anarazel@anarazel.de
<andres@anarazel.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

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Background worker processes

  2. Rearrange storage of data in xl_running_xacts.

  3. Basic binary heap implementation.

  4. Embedded list interface

  5. Refactor xlog.c to create src/backend/postmaster/startup.c