Fix: Database timeout when deleting large sources (#737)

* fix: implement CASCADE DELETE for source deletion timeout issue

- Add migration 009 to add CASCADE DELETE constraints to foreign keys
- Simplify delete_source() to only delete parent record
- Database now handles cascading deletes efficiently
- Fixes timeout issues when deleting sources with thousands of pages

* chore: update complete_setup.sql to include CASCADE DELETE constraints

- Add ON DELETE CASCADE to foreign keys in initial setup
- Include migration 009 in the migrations tracking
- Ensures new installations have CASCADE DELETE from the start

migration/0.1.0/009_add_cascade_delete_constraints.sql

@@ -0,0 +1,67 @@
+-- =====================================================
+-- Migration 009: Add CASCADE DELETE constraints
+-- =====================================================
+-- This migration adds CASCADE DELETE to foreign key constraints
+-- for archon_crawled_pages and archon_code_examples tables
+-- to fix database timeout issues when deleting large sources
+--
+-- Issue: Deleting sources with thousands of crawled pages times out
+-- Solution: Let the database handle cascading deletes efficiently
+-- =====================================================
+
+-- Start transaction for atomic changes
+BEGIN;
+
+-- Drop existing foreign key constraints
+ALTER TABLE archon_crawled_pages
+    DROP CONSTRAINT IF EXISTS archon_crawled_pages_source_id_fkey;
+
+ALTER TABLE archon_code_examples
+    DROP CONSTRAINT IF EXISTS archon_code_examples_source_id_fkey;
+
+-- Re-add foreign key constraints with CASCADE DELETE
+ALTER TABLE archon_crawled_pages
+    ADD CONSTRAINT archon_crawled_pages_source_id_fkey
+    FOREIGN KEY (source_id)
+    REFERENCES archon_sources(source_id)
+    ON DELETE CASCADE;
+
+ALTER TABLE archon_code_examples
+    ADD CONSTRAINT archon_code_examples_source_id_fkey
+    FOREIGN KEY (source_id)
+    REFERENCES archon_sources(source_id)
+    ON DELETE CASCADE;
+
+-- Add comment explaining the CASCADE behavior
+COMMENT ON CONSTRAINT archon_crawled_pages_source_id_fkey ON archon_crawled_pages IS
+    'Foreign key with CASCADE DELETE - automatically deletes all crawled pages when source is deleted';
+
+COMMENT ON CONSTRAINT archon_code_examples_source_id_fkey ON archon_code_examples IS
+    'Foreign key with CASCADE DELETE - automatically deletes all code examples when source is deleted';
+
+-- Record the migration
+INSERT INTO archon_migrations (version, migration_name)
+VALUES ('0.1.0', '009_add_cascade_delete_constraints')
+ON CONFLICT (version, migration_name) DO NOTHING;
+
+-- Commit transaction
+COMMIT;
+
+-- =====================================================
+-- Verification queries (run separately if needed)
+-- =====================================================
+-- To verify the constraints after migration:
+--
+-- SELECT
+--     tc.table_name,
+--     tc.constraint_name,
+--     tc.constraint_type,
+--     rc.delete_rule
+-- FROM information_schema.table_constraints tc
+-- JOIN information_schema.referential_constraints rc
+--     ON tc.constraint_name = rc.constraint_name
+-- WHERE tc.table_name IN ('archon_crawled_pages', 'archon_code_examples')
+--     AND tc.constraint_type = 'FOREIGN KEY';
+--
+-- Expected result: Both constraints should show delete_rule = 'CASCADE'
+-- =====================================================

migration/complete_setup.sql

@@ -223,8 +223,8 @@ CREATE TABLE IF NOT EXISTS archon_crawled_pages (
     -- Add a unique constraint to prevent duplicate chunks for the same URL
     UNIQUE(url, chunk_number),
 
-    -- Add foreign key constraint to sources table
-    FOREIGN KEY (source_id) REFERENCES archon_sources(source_id)
+    -- Add foreign key constraint to sources table with CASCADE DELETE
+    FOREIGN KEY (source_id) REFERENCES archon_sources(source_id) ON DELETE CASCADE
 );
 
 -- Multi-dimensional indexes
@@ -272,8 +272,8 @@ CREATE TABLE IF NOT EXISTS archon_code_examples (
     -- Add a unique constraint to prevent duplicate chunks for the same URL
     UNIQUE(url, chunk_number),
 
-    -- Add foreign key constraint to sources table
-    FOREIGN KEY (source_id) REFERENCES archon_sources(source_id)
+    -- Add foreign key constraint to sources table with CASCADE DELETE
+    FOREIGN KEY (source_id) REFERENCES archon_sources(source_id) ON DELETE CASCADE
 );
 
 -- Multi-dimensional indexes
@@ -990,7 +990,8 @@ VALUES
   ('0.1.0', '005_ollama_create_functions'),
   ('0.1.0', '006_ollama_create_indexes_optional'),
   ('0.1.0', '007_add_priority_column_to_tasks'),
-  ('0.1.0', '008_add_migration_tracking')
+  ('0.1.0', '008_add_migration_tracking'),
+  ('0.1.0', '009_add_cascade_delete_constraints')
 ON CONFLICT (version, migration_name) DO NOTHING;
 
 -- Enable Row Level Security on migrations table