Horton

Re: Duplicated LSN in ReorderBuffer

Alvaro Herrera <alvherre@2ndquadrant.com>

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From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Andres Freund <andres@anarazel.de>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, Ildar Musin <ildar@adjust.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Petr Jelinek <petr@2ndquadrant.com>, Simon Riggs <simon@2ndquadrant.com>
Date: 2019-08-12T21:35:58Z
Lists: pgsql-hackers 
On 2019-Aug-07, Andres Freund wrote:

> I think we would need to do this for all values of
> SnapBuildCurrentState() - after all the problem occurs because we
> *previously* didn't assign subxids to the toplevel xid.  Compared to the
> cost of catalog changes, ReorderBufferAssignChild() is really cheap. So
> I don't think there's any problem just calling it unconditionally (when
> top_xid <> xid, of course).

BTW I wrote the code as suggested and it passes all the tests ... but I
then noticed that the unpatched code doesn't fail Ildar's original
pgbench-based test for me, either.  So maybe my laptop is not powerful
enough to reproduce it, or maybe I'm doing something wrong.

I'm tempted to just push it, since it seems "obviously" more correct
than the original.

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Commits

  1. logical decoding: process ASSIGNMENT during snapshot build

  2. Ability to advance replication slots