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Re: Pg_upgrade speed for many tables

Andres Freund <andres@2ndquadrant.com>

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From: Andres Freund <andres@2ndquadrant.com>
To: Bruce Momjian <bruce@momjian.us>
Cc: Robert Haas <robertmhaas@gmail.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, Jeff Janes <jeff.janes@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Magnus Hagander <magnus@hagander.net>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2012-11-05T22:03:45Z
Lists: pgsql-hackers 
On Mon, Nov 05, 2012 at 04:42:56PM -0500, Bruce Momjian wrote:
> On Mon, Nov  5, 2012 at 04:39:27PM -0500, Robert Haas wrote:
> > On Mon, Nov 5, 2012 at 4:33 PM, Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
> > > AFAIR any transaction that modifies catalogs gets sync commit forcibly,
> > > regardless of the setting.  And sync commit means you get to wait for
> > > all previous transactions to be flushed as well.  So simply creating a
> > > temp table ought to do the trick ...

SET synchronous_commit = on;
SELECT txid_current();

Should be enough.

> > I don't think there's a carve-out for system tables ... but creating a
> > temp table with synchronous_commit=on will certainly do the trick.
>
> What is a temp table writing to WAL?  The pg_class/pg_attribute changes?

Yes.

Andres