duplicate_cursor cursor “…” already exists — 42P03

Symptoms

A DECLARE tried to create a cursor whose name is already in use in the session. PostgreSQL raises SQLSTATE 42P03 (duplicate_cursor).

• A cursor with that name already exists.
• Common when re-declaring without closing the previous one.
• Cursor names must be unique within a session.

What the server log shows

ERROR:  cursor "mycursor" already exists

Why PostgreSQL raises this — what the manual says

the DECLARE reference (Parameters):

“This must be different from any other active cursor name in the session.”

Cursor names are unique per session. Declaring a second cursor with a name still in use collides with the existing one, so PostgreSQL reports 42P03.

Common causes

• Re-declaring a cursor without closing the previous one.
• Reusing a fixed cursor name in a loop.
• A non-holdable cursor from a prior statement still open.

How to fix it

1. Close the existing cursor first: CLOSE mycursor; then re-declare.
2. Use unique cursor names, or CLOSE ALL; between iterations.
3. Wrap cursor use so each is closed when finished.

Related & next steps

• SQLSTATE 42P03 — Duplicate Cursor (full reference)
• Message: cursor does not exist
• Glossary: Cursor

Reference: PostgreSQL 18 — DECLARE.