Message-ID: <1223bd05e1482396b63c9ffc01dee7e7f357babe.camel@cybertec.at>
Subject: Re: Documentation incorrect pg_partition_root function description.
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: udv.mail@gmail.com, pgsql-docs@lists.postgresql.org
Date: Sat, 28 Feb 2026 21:12:06 +0100
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On Sat, 2026-02-28 at 08:36 +0000, PG Doc comments form wrote:
> The following documentation comment has been logged on the website:
>=20
> Page: https://www.postgresql.org/docs/18/functions-admin.html
> Description:
>=20
> https://www.postgresql.org/docs/current/functions-admin.html
>=20
> pg_partition_root ( regclass ) =E2=86=92 regclass
> Returns the top-most parent of the partition tree to which the given
> relation belongs. Returns NULL if the relation does not exist or is not a
> partition or partitioned table.
>=20
> "does not exist" is not correct description, if table does not exist, we'=
ll
> get an error, not NULL:
>=20
> EXAMPLE:
> SELECT * FROM pg_partition_root( 'nonexisting_table' );
>=20
> RESULT:
> SQL Error [42P01]: ERROR: relation "nonexisting_table" does not exist
> Position: 34

The error you are getting is *not* from pg_partition_root(), but from the
cast from "text" to "regclass":

  SELECT 'nonexisting_table'::regclass;
  ERROR:  relation "nonexisting_table" does not exist
  LINE 1: SELECT 'nonexisting_table'::regclass;
                 ^

And if you take a "regclass" that corresponds to an object ID that is not
the object ID of any existing relation, you get a NULL result:

  SELECT pg_partition_root('12345'::regclass);

   pg_partition_root=20
  -------------------
 =20
  (1 row)

Yours,
Laurenz Albe