Re: pg_upgrade < 9.3 -> >=9.3 misses a step around multixacts

On Tue, Jul  1, 2014 at 03:30:47PM -0400, Bruce Momjian wrote:
> > * When upgrading from 9.2 or older, all tables need to have relminmxid
> >   set to oldestMulti.  However, since pg_dump --binary-upgrade cannot
> >   extract useful values from the catalog, we will need to have the
> >   schema load create all tables with relminmxid=0.  A subsequent UPDATE
> >   will fix the values.
>
> OK, the updated attached patch does this.  It repurposes
> set_frozenxids().

OK, patch applied back through 9.3.  This leaves the two queries users
are going to have to run in 9.3.X.  The first will tell users if they
should remove offsets/0000:

    WITH list(file) AS
    (
        SELECT * FROM pg_ls_dir('pg_multixact/offsets')
    )
    SELECT     EXISTS (SELECT * FROM list WHERE file = '0000') AND
        NOT EXISTS (SELECT * FROM list WHERE file = '0001') AND
        NOT EXISTS (SELECT * FROM list WHERE file = 'FFFF') AND
        EXISTS (SELECT * FROM list WHERE file != '0000')
        AS file_0000_removal_required;

The second will tell them if they should go to a wiki page that will
show them how to set database and relation minmxid values:

    WITH list(file) AS
    (
        SELECT * FROM pg_ls_dir('pg_multixact/offsets')
    )
    SELECT     EXISTS (SELECT * FROM list WHERE file ~ '^[8-9A-F]') AND
        EXISTS (SELECT * FROM pg_database WHERE datminmxid = 1)
        AS update_database_and_relation_minmxid;

I will work on the wiki page now.

I think this issue is now ready for 9.3.X, once we write the wiki page
and release note text.

--
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + Everyone has their own god. +