duplicate_schema schema “…” already exists — 42P06

Symptoms

A CREATE SCHEMA tried to create a schema whose name already exists in the database. PostgreSQL raises SQLSTATE 42P06 (duplicate_schema).

• A schema with that name already exists.
• Schema names are unique within a database.
• Common in re-run migrations.

What the server log shows

ERROR:  schema "reporting" already exists

Why PostgreSQL raises this — what the manual says

As the CREATE SCHEMA reference (Description) explains:

A schema with that name already exists in the current database; schema names must be unique per database — choose a different name or add IF NOT EXISTS to skip creation when it already exists.

Schema names are unique within a database. Creating one that already exists collides with the existing schema, so PostgreSQL reports 42P06.

Common causes

• Re-running a migration that creates the schema.
• The schema was created earlier.
• A name clash with an existing schema.

How to fix it

1. Use CREATE SCHEMA IF NOT EXISTS for idempotency.
2. Check existence via \dn or pg_namespace.
3. Choose a unique schema name.

Related & next steps

• SQLSTATE 42P06 — Duplicate Schema (full reference)
• Message: database already exists
• Glossary: Schema

Reference: PostgreSQL 18 — CREATE SCHEMA.