Re: pg_dump, ATTACH, and independently restorable child partitions

Justin Pryzby <pryzby@telsasoft.com>

From: Justin Pryzby <pryzby@telsasoft.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: David Rowley <drowley@postgresql.org>, pgsql-hackers@lists.postgresql.org
Date: 2020-10-24T19:59:49Z
Lists: pgsql-hackers

Attachments

On Fri, Oct 23, 2020 at 12:29:40AM -0500, Justin Pryzby wrote:
> Since this commit, pg_dump CREATEs tables and then ATTACHes them:
> 
> |commit 33a53130a89447e171a8268ae0b221bb48af6468
> |Author: Alvaro Herrera <alvherre@alvh.no-ip.org>
> |Date:   Mon Jun 10 18:56:23 2019 -0400
> |
> |    Make pg_dump emit ATTACH PARTITION instead of PARTITION OF (reprise)
> |...
> |    This change also has the advantage that the partition is restorable from
> |    the dump (as a standalone table) even if its parent table isn't
> |    restored.
> 
> I like the idea of child tables being independently restorable, but it doesn't
> seem to work.
...
> Now that I look, it seems like this is calling PQexec(), which sends a single,
> "simple" libpq message with:
> |CREATE TABLE ..; ALTER TABLE .. ATTACH PARTITION;
> ..which is transactional, so when the 2nd command fails, the CREATE is rolled back.
> https://www.postgresql.org/docs/9.5/libpq-exec.html#LIBPQ-EXEC-MAIN

The easy fix is to add an explicit begin/commit.

-- 
Justin

Commits

  1. pg_dump: label INDEX ATTACH ArchiveEntries with an owner.

  2. Dump ALTER TABLE ... ATTACH PARTITION as a separate ArchiveEntry.

  3. Make pg_dump emit ATTACH PARTITION instead of PARTITION OF (reprise)