Re: Pg_upgrade and toast tables bug discovered

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Andres Freund <andres(at)2ndquadrant(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Pg_upgrade and toast tables bug discovered
Date: 2014-07-10 22:38:26
Message-ID: 20140710223826.GD7366@momjian.us
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On Thu, Jul 10, 2014 at 06:17:14PM -0400, Bruce Momjian wrote:
> Well, we are going to need to call internal C functions, often bypassing
> their typical call sites and the assumption about locking, etc. Perhaps
> this could be done from a plpgsql function. We could add and drop a
> dummy column to force TOAST table creation --- we would then only need a
> way to detect if a function _needs_ a TOAST table, which was skipped in
> binary upgrade mode previously.
>
> That might be a minimalistic approach.

I have thought some more on this. I thought I would need to open
pg_class in C and do complex backend stuff, but I now realize I can do
it from libpq, and just call ALTER TABLE and I think that always
auto-checks if a TOAST table is needed. All I have to do is query
pg_class from libpq, then construct ALTER TABLE commands for each item,
and it will optionally create the TOAST table if needed. I just have to
use a no-op ALTER TABLE command, like SET STATISTICS.

I am in Asia the next two weeks but will work on it after I return.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ Everyone has their own god. +

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