Re: Bogus pg_class.relminmxid value for pg_database

Heikki Linnakangas wrote:
> Right after a fresh initdb on a 9.3 or master database:
>
> postgres=# select oid,relname,relminmxid from pg_class where
> relname='pg_database';
> oid | relname | relminmxid
> ------+-------------+------------
> 1262 | pg_database | 4244967297
> (1 row)
>
> That bogus value seems to appear already some time during initdb.
> The relminmxid for all other tables is 1, which is correct.

I finally figured the source of this issue: it's caused by VACUUM FULL
(executed by initdb while copying template1 into template0): we're
missing a protection that relminmxid doesn't go backwards when swapping
heaps. We already have such a check for xids.

This is mostly innocuous, but I'm about to push the attached fix all the
same, backpatched to 9.3. (The extra context lines make the patch very
clear.)

--
Álvaro Herrera http://www.2ndQuadrant.com/
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