dependent_objects_still_exist cannot drop column … of table … because other objects depend on it — 2BP01

Symptoms

A DROP COLUMN (or similar) was blocked because other objects depend on the column. PostgreSQL raises SQLSTATE 2BP01 (dependent_objects_still_exist) and lists the dependents.

• Views, constraints, indexes, or rules depend on the column.
• A DETAIL/HINT lists dependents and suggests CASCADE.
• Default behaviour is RESTRICT (block the drop).

What the server log shows

ERROR:  cannot drop column amount of table orders because other objects depend on it
DETAIL:  view orders_summary depends on column amount
HINT:  Use DROP ... CASCADE to drop the dependent objects too.

Why PostgreSQL raises this — what the manual says

Section 5.14 Dependency Tracking:

“Almost all DROP commands in PostgreSQL support specifying CASCADE.”

PostgreSQL records inter-object dependencies in pg_depend. Dropping a column that others rely on would leave them broken, so under the default RESTRICT it blocks the drop with 2BP01 unless you cascade.

Common causes

• A view/index/constraint referencing the column.
• A rule or trigger depending on the column.
• Generated columns or defaults referencing it.

How to fix it

1. Drop or adjust the dependent objects first, then drop the column.
2. Use DROP COLUMN … CASCADE if you intend to remove dependents too (review the list).
3. Inspect dependents before deciding (the DETAIL lists them).

Related & next steps

• SQLSTATE 2BP01 — Dependent Objects Still Exist (full reference)
• Message: cannot alter type of a column used by a view or rule
• Glossary: Dependency

Reference: PostgreSQL 18 Section 5.15 “Dependency Tracking”.