docs: add guide for removing foreign data wrappers

- Add comprehensive guide for removing FDWs
- Cover both native and WASM wrapper cleanup
- Include verification steps
- Fixes #177

Co-Authored-By: [email protected] <[email protected]>

docs/guides/removing-wrappers.md

@@ -0,0 +1,86 @@
+# Removing Foreign Data Wrappers
+
+This guide explains how to fully remove a foreign data wrapper from your PostgreSQL database.
+
+## Components to Remove
+
+When removing a foreign data wrapper, you need to remove several components in the correct order:
+
+1. Foreign Tables
+2. Foreign Servers
+3. Extension
+4. (For WASM wrappers only) Cache files
+
+## Step-by-Step Removal Process
+
+### 1. List and Remove Foreign Tables
+
+First, list all foreign tables associated with your wrapper:
+
+```sql
+SELECT foreign_table_schema, foreign_table_name
+FROM information_schema.foreign_tables;
+```
+
+Remove each foreign table:
+
+```sql
+DROP FOREIGN TABLE IF EXISTS [schema_name.]table_name;
+```
+
+### 2. Remove Foreign Servers
+
+List servers:
+
+```sql
+SELECT srvname, fdwname
+FROM pg_foreign_server fs
+JOIN pg_foreign_data_wrapper fdw ON fs.srvfdw = fdw.oid;
+```
+
+Remove each server:
+
+```sql
+DROP SERVER IF EXISTS server_name CASCADE;
+```
+
+### 3. Remove the Extension
+
+```sql
+DROP EXTENSION IF EXISTS wrappers CASCADE;
+```
+
+### 4. Additional Steps for WASM Wrappers
+
+WASM wrappers cache their compiled code locally. To fully clean up:
+
+1. Stop the PostgreSQL server
+2. Remove cached WASM files:
+   ```bash
+   rm -rf /var/lib/postgresql/[version]/wasm_cache/*
+   ```
+3. Restart the PostgreSQL server
+
+## Verification
+
+After removal, verify that all components are gone:
+
+```sql
+-- Check for remaining foreign tables
+SELECT foreign_table_schema, foreign_table_name
+FROM information_schema.foreign_tables;
+
+-- Check for remaining servers
+SELECT srvname, fdwname
+FROM pg_foreign_server fs
+JOIN pg_foreign_data_wrapper fdw ON fs.srvfdw = fdw.oid;
+
+-- Check for the extension
+SELECT * FROM pg_extension WHERE extname = 'wrappers';
+```
+
+## Common Issues
+
+- Always use CASCADE when dropping servers if you're unsure about dependencies
+- For production environments, take a backup before removing components
+- Some wrappers might have additional cleanup steps; check wrapper-specific documentation

docs/index.md

@@ -67,3 +67,16 @@ Although a foreign table behaves like any other table, the data is not stored in
 The following Postgres providers support Wrappers:
 
 - [supabase.com](https://supabase.com)
+
+## Guides
+
+Learn how to use and manage Foreign Data Wrappers:
+
+- [Installing Wrappers](guides/installation.md)
+- [Removing Wrappers](guides/removing-wrappers.md)
+- [Native vs WASM Wrappers](guides/native-wasm.md)
+- [Query Pushdown](guides/query-pushdown.md)
+- [Remote Subqueries](guides/remote-subqueries.md)
+- [Usage Statistics](guides/usage-statistics.md)
+- [Security](guides/security.md)
+- [Limitations](guides/limitations.md)