docs: add guide for removing foreign data wrappers (#390)

* 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: update SQL queries to use lowercase and pg_catalog

- Convert all SQL queries to lowercase
- Replace information_schema with pg_catalog
- Add full table qualification
- Improve query readability with column aliases

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

* docs: update SQL queries and remove WASM cleanup steps

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

* docs: update SQL queries with aliases and remove verification section

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

* Update docs/guides/removing-wrappers.md

* Update docs/guides/removing-wrappers.md

* Update docs/guides/removing-wrappers.md

* Update docs/guides/removing-wrappers.md

* docs: add removing wrappers guide to nav list

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: [email protected] <[email protected]>
Co-authored-by: Oliver Rice <[email protected]>
Co-authored-by: Bo Lu <[email protected]>

docs/guides/removing-wrappers.md

@@ -0,0 +1,64 @@
+# Removing Foreign Data Wrappers
+
+This guide explains how to fully remove all foreign data wrappers 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. Wrappers Extension
+
+## Step-by-Step Removal Process
+
+### 1. List and Remove Foreign Tables
+
+First, list all foreign tables associated with your wrapper:
+
+```sql
+select c.relname as foreign_table_name,
+       n.nspname as schema_name
+from pg_catalog.pg_foreign_table ft
+join pg_catalog.pg_class c on c.oid = ft.ftrelid
+join pg_catalog.pg_namespace n on n.oid = c.relnamespace;
+```
+
+Remove each foreign table:
+
+```sql
+drop foreign table if exists schema_name.table_name;
+```
+
+### 2. Remove Foreign Servers
+
+List servers:
+
+```sql
+select fs.srvname as server_name,
+       fdw.fdwname as wrapper_name
+from pg_catalog.pg_foreign_server fs
+join pg_catalog.pg_foreign_data_wrapper fdw on fdw.oid = fs.srvfdw;
+```
+
+Remove each server:
+
+```sql
+drop server if exists server_name cascade;
+```
+
+!!! note
+
+    With `cascade` option, this will also drop all foreign tables using that foreign server.
+
+### 3. Remove the Extension
+
+```sql
+drop extension if exists wrappers cascade;
+```
+
+!!! note
+
+    With `cascade` option, this will also drop all foreign servers and foreign tables using Wrappers extension.
+

mkdocs.yaml

@@ -41,6 +41,7 @@ nav:
         - Security: 'guides/security.md'
         - FDW Statistics: 'guides/usage-statistics.md'
         - Installing Wrappers in Postgres: 'guides/installation.md'
+        - Removing Foreign Data Wrappers: 'guides/removing-wrappers.md'
         - Limitations: 'guides/limitations.md'
         - Developing a Wasm Wrapper: 
             - Quick Start: 'guides/create-wasm-wrapper.md'