undefined_object index “…” does not exist — 42704

Symptoms

A statement referenced an index that does not exist. PostgreSQL raises SQLSTATE 42704 (undefined_object).

• The named index isn’t defined.
• Common in DROP INDEX/ALTER INDEX/REINDEX.
• Index names live in a schema like tables.

What the server log shows

ERROR:  index "idx_orders_customer" does not exist

Why PostgreSQL raises this — what the manual says

the DROP INDEX reference (Description):

“A normal DROP INDEX acquires an ACCESS EXCLUSIVE lock on the table, blocking other accesses until the index drop can be completed.”

Indexes are named schema objects. Referencing a name that doesn’t exist (typo, already dropped, or wrong schema/search_path) cannot be resolved, so PostgreSQL reports 42704.

Common causes

• A typo or wrong case in the index name.
• The index was already dropped or never created.
• It lives in a schema not on the search_path.

How to fix it

1. List indexes: \di or query pg_indexes.
2. Use the exact (optionally schema-qualified) index name.
3. Use DROP INDEX IF EXISTS for idempotency.

Related & next steps

• SQLSTATE 42704 — Undefined Object (full reference)
• Message: tablespace does not exist
• Glossary: Index

Reference: PostgreSQL 18 — DROP INDEX.