Date: Thu, 9 Oct 2014 07:07:00 -0700 (PDT)
From: jim_yates <pg@wg5jim.net>
To: pgsql-sql@postgresql.org
Message-ID: <1412863620263-5822376.post@n5.nabble.com>
In-Reply-To: <20141008205416.GZ7043@eldon.alvh.no-ip.org>
References: <1412791213607-5822248.post@n5.nabble.com>
 <20141008185538.GY7043@eldon.alvh.no-ip.org>
 <1412797415000-5822268.post@n5.nabble.com>
 <20141008205416.GZ7043@eldon.alvh.no-ip.org>
Subject: Re: could not access status of transaction pg_multixact issue
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Alvaro Herrera-9 wrote
> jim_yates wrote:
>=20
>> > A better way not involving mxid_age() would be to use pg_controldata to
>> > extract the current value of the mxid counter, then subtract the
>> current
>> > relminmxid from that value.
>>=20
>>=20
>> It's not clear which lines from pg_controldata to use for updating
>> pg_database.datminmxid.
>=20
> The one labelled NextMultiXactId.
>=20
>> I also assume I would do the pg_database update on a idle database.
>=20
> It doesn't matter, actually.  pg_database is a shared catalog, so an
> update would affect all the databases.
>=20
> --=20
> =C3=81lvaro Herrera                http://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Training & Services

I tried doing the update to pg_database on my Dev server and I can't get it
to work.  How do I calculate the new datminmxid value?

NextMultiXactId:  30349  relminmxid from pg_class for the table: 8376

If I subtract the relminmxid from the nextmulixact I get 21793 which won't
work.

production-copy=3D# update pg_database set datminmxid=3D21973 where
datname=3D'production-copy';
ERROR:  column "datminmxid" is of type xid but expression is of type integer


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