From: Ed Sabol <edwardjsabol@gmail.com>
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Date: Wed, 18 Feb 2026 20:47:27 -0500
Subject: Duplicate key value violates unique constraint
 "pg_type_typname_nsp_index" error
Message-Id: <1D3D88D6-5E8C-4144-BF79-DB531FE4FE39@gmail.com>
To: Pgsql-admin <pgsql-admin@lists.postgresql.org>
Archived-At: 
 <https://www.postgresql.org/message-id/1D3D88D6-5E8C-4144-BF79-DB531FE4FE39%40gmail.com>
Precedence: bulk

Using PostgreSQL 15.16, I have some SQL for creating a materialized view =
that's inside a larger transaction which randomly emits the following =
error:

ERROR:  duplicate key value violates unique constraint =
"pg_type_typname_nsp_index"
DETAIL:  Key (typname, typnamespace)=3D(largetable, 20488) already =
exists.

The error doesn't happen 100% of the times I try to execute this =
transaction. Maybe 30% of the time? Also, I've had it happen on multiple =
separate PostgreSQL servers.

I'm not entirely sure how to interpret these ERROR and DETAIL messages. =
Can someone explain it?

I've tried the following queries to try to figure out what typnamespace =
=3D 20488 refers to:

SELECT nspname FROM pg_namespace WHERE oid =3D 20488;
SELECT count(*) FROM pg_catalog.pg_type WHERE typname =3D 'targetable' =
AND typnamespace =3D 20488;

Neither query provides any useful information. The latter always returns =
zero immediately immediately prior to the SQL error.

Here's the (slightly sanitized) SQL which causes the error:

CREATE MATERIALIZED VIEW someschema.largetable AS
(
   SELECT=20
      row_number() OVER () AS __row,
      sub.*,
      public.somefunc1(afield) AS s_result1,
      public.somefunc2(anotherfield) AS s_result2,
      public.somefunc3(somefield1, somefield2) AS s_result3
   FROM (
      SELECT * FROM someschema.largetable_upd_1
      UNION ALL SELECT * FROM someschema.largetable_upd_2
      UNION ALL SELECT * FROM someschema.largetable_upd_3
      UNION ALL SELECT * FROM someschema.largetable_upd_4
      UNION ALL SELECT * FROM someschema.largetable_upd_5
      UNION ALL SELECT * FROM someschema.largetable_upd_6
      UNION ALL SELECT * FROM someschema.largetable_upd_8
      UNION ALL SELECT * FROM someschema.largetable_upd_9
      UNION ALL SELECT * FROM someschema.largetable_upd_10
   ) sub
);

public.somefunc1, public.somefunc2, and public.somefunc3 return three =
types defined in PgSphere. I have the latest PgSphere installed.
Any ideas as to how to eliminate the error?

My first thought was to change the asterisks to explicit lists of =
columns.

Any assistance would be appreciated!

Thanks,
Ed