duplicate_object role “…” already exists — 42710

Symptoms

A CREATE ROLE/CREATE USER tried to create a role whose name already exists. PostgreSQL raises SQLSTATE 42710 (duplicate_object).

• A role with that name already exists.
• Roles are cluster-wide (shared across databases).
• Common in idempotent provisioning scripts.

What the server log shows

ERROR:  role "app_user" already exists

Why PostgreSQL raises this — what the manual says

As the CREATE ROLE reference (Description) explains:

A role with that name already exists; role names must be unique across the entire cluster, so choose a different name or use ALTER ROLE to modify the existing one.

Role names are unique cluster-wide. Creating one that already exists collides with the existing role, so PostgreSQL reports 42710.

Common causes

• Re-running a provisioning script that creates the role.
• The role was created earlier (roles are cluster-wide).
• A name clash with a pre-existing role.

How to fix it

1. Skip creation if it exists: check pg_roles or use DO/conditional logic.
2. Use CREATE ROLE … only when absent; otherwise ALTER ROLE to adjust.
3. Choose a unique role name.

Related & next steps

• SQLSTATE 42710 — Duplicate Object (full reference)
• Message: type already exists
• Glossary: Role

Reference: PostgreSQL 18 — CREATE ROLE.