Re: Allow table AMs to define their own reloptions - Mailing list pgsql-hackers

On Thu, 4 Jun 2026 at 04:32, Andrew Dunstan <andrew@dunslane.net> wrote:

On 2025-05-26 Mo 7:06 AM, Julien Tachoires wrote:
> On Sat, Mar 29, 2025 at 08:46:01AM +0100, Julien Tachoires wrote:
>> On Sun, Mar 02, 2025 at 02:23:54PM +0100, Julien Tachoires wrote:
>>> On Sun, Mar 02, 2025 at 09:56:41AM +0100, Julien Tachoires wrote:
>>>> With the help of the new TAM routine 'relation_options', table access
>>>> methods can with this patch define their own reloptions
>>>> parser/validator.
>>>>
>>>> These reloptions can be set via the following commands:
>>>> 1. CREATE TABLE ... USING table_am
>>>>         WITH (option1='value1', option2='value2');
>>>> 2. ALTER TABLE ...
>>>>         SET (option1 'value1', option2 'value2');
>>>> 3. ALTER TABLE ... SET ACCESS METHOD table_am
>>>>         OPTIONS (option1 'value1', option2 'value2');
>>>>
>>>> When changing table's access method, the settings inherited from the
>>>> former TAM can be dropped (if not supported by the new TAM) via: DROP
>>>> option, or, updated via: SET option 'value'.
>>>>
>>>> Currently, tables using different TAMs than heap are able to use heap's
>>>> reloptions (fillfactor, toast_tuple_target, etc...). With this patch
>>>> applied, this is not the case anymore: if the TAM needs to have access
>>>> to similar settings to heap ones, they have to explicitly define them.
>>>>
>>>> The 2nd patch file includes a new test module 'dummy_table_am' which
>>>> implements a dummy table access method utilized to exercise TAM
>>>> reloptions. This test module is strongly based on what we already have
>>>> in 'dummy_index_am'. 'dummy_table_am' provides a complete example of TAM
>>>> reloptions definition.
>>>>
>>>> This work is directly derived from SadhuPrasad's patch here [2]. Others
>>>> attempts were posted here [1] and here [3].
>>>>
>>>> [1] https://www.postgresql.org/message-id/flat/429fb58fa3218221bb17c7bf9e70e1aa6cfc6b5d.camel%40j-davis.com
>>>> [2] https://www.postgresql.org/message-id/flat/CAFF0-CG4KZHdtYHMsonWiXNzj16gWZpduXAn8yF7pDDub+GQMg@mail.gmail.com
>>>> [3] https://www.postgresql.org/message-id/flat/AMUA1wBBBxfc3tKRLLdU64rb.1.1683276279979.Hmail.wuhao%40hashdata.cn
>>> Please find a new version including minor fixes: 'TAM' terms are
>>> replaced by 'table AM'
>> Please find a new rebased version.
> New rebased version.
>


This thread seems to have gone dormant, sadly. Here's a fresh attempt I
made (with assistance from Claude), before I was aware of the existence
of this and other efforts. I think it meets most of the previous
objections, and is in line with what we do for Index AMs.

I was testing this patch and found this issue,

CREATE EXTENSION dummy_table_am;

CREATE TABLE t (a int) USING dummy_table_am WITH (option_int = 42);

ALTER TABLE t SET ACCESS METHOD heap;

SELECT reloptions FROM pg_class WHERE oid = 't'::regclass;

  reloptions    
-----------------
 {option_int=42}
(1 row)
ALTER TABLE t SET (fillfactor = 50);
2026-07-16 19:01:36.060 IST [95058] ERROR:  unrecognized parameter "option_int"
2026-07-16 19:01:36.060 IST [95058] STATEMENT:  ALTER TABLE t SET (fillfactor = 50);
ERROR:  unrecognized parameter "option_int"

Basically, the option is left behind after changing the tableam to heap, I think that isn't intentional.