Re: Postgres Partitions Limitations (5.11.2.3)

On Fri, 2023-01-06 at 08:28 +0000, PG Doc comments form wrote:
> The following documentation comment has been logged on the website:
>
> Page: https://www.postgresql.org/docs/15/ddl-partitioning.html
> Description:
>
> Link:
> https://www.postgresql.org/docs/current/ddl-partitioning.html#DDL-PARTITIONING-DECLARATIVE
>
> "Using ONLY to add or drop a constraint on only the partitioned table is
> supported as long as there are no partitions. Once partitions exist, using
> ONLY will result in an error. Instead, constraints on the partitions
> themselves can be added and (if they are not present in the parent table)
> dropped." This seems in contradiction to the example involving adding a
> unique constraint while minimizing locking at the bottom of "5.11.2.2.
> Partition Maintenance", which seems to run fine on my local Pg instance:
>
> "
> This technique can be used with UNIQUE and PRIMARY KEY constraints too; the
> indexes are created implicitly when the constraint is created. Example:
>
> ```ALTER TABLE ONLY measurement ADD UNIQUE (city_id, logdate);
>
> ALTER TABLE measurement_y2006m02 ADD UNIQUE (city_id, logdate);
> ALTER INDEX measurement_city_id_logdate_key
>     ATTACH PARTITION measurement_y2006m02_city_id_logdate_key;
> ...
> ```
> "
>
> I might be misinterpreting something. Sorry if that's the case!

No, that is actually an omission in the documentation.

The attached patch tries to improve that.

Yours,
Laurenz Albe