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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: 2023-07-17T02:37:28Z
Lists: pgsql-hackers 
On Thu, Jun 01, 2023 at 08:50:50AM -0400, Michael Paquier wrote:
> >> Speaking of which, ATExecSetAccessMethodNoStorage() does a catalog
> >> update even if ALTER TABLE is defined to use the same table AM as what
> >> is currently set.  There is no need to update the relation's pg_class
> >> entry in this case.  Be careful that InvokeObjectPostAlterHook() still
> >> needs to be checked in this case.  Perhaps some tests should be added
> >> in test_oat_hooks.sql?  It would be tempted to add a new SQL file for
> >> that.
> >
> > Are you suggesting to put this in a conditional: if oldrelam!=newAccessMethod ?
> 
> Yes, that's what I would add with a few lines close to the beginning
> of ATExecSetTableSpaceNoStorage() to save from catalog updates if
> these are not needed.

I understand that it's possible for it to be conditional, but I don't
undertand why it's desirable/important ?

It still seems preferable to be unconditional.

On Wed, May 31, 2023 at 06:35:34PM -0500, Justin Pryzby wrote:
>> Why is that desirable ?  I'd prefer to see it written with fewer
>> conditionals, not more; then, it hits the same path every time.

It's not conditional in the tablespace code that this follows, nor
others like ATExecSetStatistics(), ATExecForceNoForceRowSecurity(),
ATExecSetCompression(), etc, some of which are recently-added.  If it's
important to do here, isn't it also important to do everywhere else ?

-- 
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