How to Uninstall ClickHouse Extension in PostgreSQL

Galaxy Glossary

How do I completely uninstall the ClickHouse extension from PostgreSQL?

DROP EXTENSION fully removes the ClickHouse FDW extension and all its objects from the current PostgreSQL database.

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Description

Example H2

Example H3

Why remove ClickHouse FDW?

Unload the extension when you migrate queries back to native tables, decommission ClickHouse, or tidy unused dependencies. This frees shared libraries and avoids confusion for new engineers.

What is the uninstall command?

Use DROP EXTENSION clickhouse_fdw; to delete the extension. Add IF EXISTS to avoid errors if it is already gone. Add CASCADE to drop dependent foreign tables automatically.

When should I use CASCADE vs RESTRICT?

Choose CASCADE when you no longer need any foreign tables that rely on ClickHouse.Choose RESTRICT (default) when you plan to migrate those tables first; the command will abort if dependencies exist.

Step-by-step uninstall workflow

1. Confirm the extension \dx clickhouse_fdw.
2. Migrate or drop foreign tables: CREATE TABLE orders_pg AS TABLE orders_ch;
3. Remove servers and user mappings if needed.
4. Run DROP EXTENSION IF EXISTS clickhouse_fdw CASCADE;
5. Verify with \dx.

Does it affect other databases?

Extensions are database-local. You must repeat the command in every database that loaded ClickHouse FDW.Dropping it in postgres does not remove it from analytics.

Best practices for safe removal

• Take a backup with pg_dump.
• Migrate critical data.
• Check application code for remaining foreign table references.
• Drop user mappings and servers to keep the catalog clean.

Quick checklist before running DROP EXTENSION

✓ No production queries run against foreign tables.
✓ All data replicated or archived.
✓ You are connected to the correct database.
✓ Proper privileges (superuser or owner).

Why How to Uninstall ClickHouse Extension in PostgreSQL is important

How to Uninstall ClickHouse Extension in PostgreSQL Example Usage


-- Migrate data, then remove ClickHouse FDW
BEGIN;
-- Copy remote orders into local table
CREATE TABLE Orders_Local AS
SELECT * FROM Orders;           -- Orders is a ClickHouse foreign table
-- Remove foreign table
DROP FOREIGN TABLE Orders;
-- Uninstall extension
DROP EXTENSION IF EXISTS clickhouse_fdw CASCADE;
COMMIT;

How to Uninstall ClickHouse Extension in PostgreSQL Syntax


DROP EXTENSION [IF EXISTS] clickhouse_fdw [CASCADE | RESTRICT];

-- Example with safety checks
-- 1. Confirm extension
\dx clickhouse_fdw
-- 2. Uninstall only if present and force-remove dependents
DROP EXTENSION IF EXISTS clickhouse_fdw CASCADE;

Common Mistakes

Forgetting CASCADE: If foreign tables still depend on the extension, DROP EXTENSION without CASCADE fails with error “dependent objects exist.” Fix by migrating/dropping the tables or rerunning with CASCADE.
Running DROP EXTENSION in the wrong database: Extensions are database-scoped, so the command silently does nothing in an unrelated database. Always connect to the database that actually loaded ClickHouse FDW.