wrong_object_type “…” is a foreign table — 42809

Symptoms

An operation valid only for ordinary tables was applied to a foreign table. PostgreSQL raises SQLSTATE 42809 (wrong_object_type).

• The relation is a foreign table managed by an FDW.
• Some local-table commands don’t apply to foreign tables.
• Use foreign-table-specific commands instead.

What the server log shows

ERROR:  "remote_orders" is a foreign table
DETAIL:  Certain commands are not supported on foreign tables.

Why PostgreSQL raises this — what the manual says

Section 5.12 Foreign Data:

“A foreign table can be used in queries just like a normal table, but a foreign table has no storage in the PostgreSQL server.”

Foreign tables proxy data in an external source via a foreign data wrapper; they have no local storage. Commands assuming local storage are not applicable and PostgreSQL rejects them with 42809.

Common causes

• Applying a storage-specific command to a foreign table.
• Confusing a foreign table with a local table.
• Operations the FDW does not support.

How to fix it

1. Use ALTER FOREIGN TABLE and FDW-appropriate operations.
2. Perform storage operations on the underlying source instead.
3. Check the object kind with \d remote_orders.

Related & next steps

• SQLSTATE 42809 — Wrong Object Type (full reference)
• Message: relation is not a table
• Glossary: Foreign data wrapper

Reference: PostgreSQL 18 Section 5.12 “Foreign Data”.