undefined_object extension “…” is not available — 42704

Symptoms

A command referenced an extension that is not available (its control/script files are not installed on the server). PostgreSQL raises SQLSTATE 42704 (undefined_object).

• The named extension isn’t available to install.
• Common when the extension package isn’t on the server.
• Distinct from “already exists”.

What the server log shows

ERROR:  extension "postgis" is not available
DETAIL:  Could not open extension control file "/usr/share/postgresql/extension/postgis.control": No such file or directory.
HINT:  The extension must first be installed on the system where PostgreSQL is running.

Why PostgreSQL raises this — what the manual says

the CREATE EXTENSION reference (Notes):

“Before you can use CREATE EXTENSION to load an extension into a database, the extension’s supporting files must be installed.”

CREATE EXTENSION loads from on-disk control/script files. If those files aren’t installed at the OS level, the extension can’t be resolved, so PostgreSQL reports 42704.

Common causes

• The extension’s OS package isn’t installed on the server.
• A typo in the extension name.
• The extension files are in a different PostgreSQL installation.

How to fix it

1. Install the extension package on the server (e.g. postgresql-contrib or the vendor package).
2. List available extensions: SELECT * FROM pg_available_extensions;.
3. Then run CREATE EXTENSION postgis;.

Related & next steps

• SQLSTATE 42704 — Undefined Object (full reference)
• Message: extension already exists
• Glossary: Extension

Reference: PostgreSQL 18 — CREATE EXTENSION.