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Re: ALTER TABLE SET ACCESS METHOD on partitioned tables

Justin Pryzby <pryzby@telsasoft.com>

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From: Justin Pryzby <pryzby@telsasoft.com>
To: Michael Paquier <michael@paquier.xyz>
Cc: Soumyadeep Chakraborty <soumyadeep2007@gmail.com>, Zhihong Yu <zyu@yugabyte.com>, pgsql-hackers@postgresql.org, Ashwin Agrawal <ashwinstar@gmail.com>, vanjared@vmware.com
Date: 2023-03-30T05:07:58Z
Lists: pgsql-hackers

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On Mon, Mar 27, 2023 at 11:34:36PM -0500, Justin Pryzby wrote:
> On Tue, Mar 28, 2023 at 09:13:10AM +0900, Michael Paquier wrote:
> > On Mon, Mar 20, 2023 at 09:30:50AM +0900, Michael Paquier wrote:
> > > Did you check dump and restore flows with partition
> > > trees and --no-table-access-method?  Perhaps there should be
> > > some regression tests with partitioned tables?
> > 
> > I was looking at the patch, and as I suspected the dumps generated
> > are forgetting to apply the AM to the partitioned tables.
> 
> The patch said:
> 
> +       else if (RELKIND_HAS_TABLE_AM(relkind) || relkind == RELKIND_PARTITIONED_TABLE)
> 
> pg_dump was missing a similar change that's conditional on
> RELKIND_HAS_TABLE_AM().  It looks like those are the only two places
> that need be be specially handled.
> 
> I dug up my latest patch from 2021 and incorporated the changes from the
> 0001 patch here, and added a test case.
> 
> I realized that one difference with tablespaces is that, as written,
> partitioned tables will *always* have an AM specified,  and partitions
> will never use default_table_access_method.  Is that what's intended ?
> 
> Or do we need logic similar tablespaces, such that the relam of a
> partitioned table is set only if it differs from default_table_am ?

Actually .. I think it'd be a mistake if the relam needed to be
interpretted differently for partitioned tables than other relkinds.

I updated the patch to allow intermediate partitioned tables to inherit
relam from their parent.

Michael wrote:
> .. and there are quite more points to consider.

What more points ?  There's nothing that's been raised here.  In fact,
your message last week is the first comment since last June ..

-- 
Justin

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Add information about access method for partitioned relations in \dP+

  2. Fix dumps of partitioned tables with table AMs

  3. Don't use the pg_am system catalog in new test

  4. ALTER TABLE: rework determination of access method ID

  5. Allow specifying an access method for partitioned tables

  6. Review wording on tablespaces w.r.t. partitioned tables

  7. Add support for DEFAULT in ALTER TABLE .. SET ACCESS METHOD

  8. Update comment of AlterTableCmd->name in parsenodes.h