Ticket CV2-5653 [WIP]: Adding migration related to last commit

db/migrate/20241123135242_add_trigger_to_relationships_table.rb

@@ -0,0 +1,37 @@
+class AddTriggerToRelationshipsTable < ActiveRecord::Migration[6.1]
+  def up
+    # Create the trigger function
+    execute <<~SQL
+      CREATE OR REPLACE FUNCTION validate_relationships()
+      RETURNS TRIGGER AS $$
+      BEGIN
+          -- Check if source_id exists as a target_id
+          IF EXISTS (SELECT 1 FROM relationships WHERE target_id = NEW.source_id) THEN
+              RAISE EXCEPTION 'source_id % already exists as a target_id', NEW.source_id;
+          END IF;
+
+          -- Check if target_id exists as a source_id
+          IF EXISTS (SELECT 1 FROM relationships WHERE source_id = NEW.target_id) THEN
+              RAISE EXCEPTION 'target_id % already exists as a source_id', NEW.target_id;
+          END IF;
+
+          RETURN NEW;
+      END;
+      $$ LANGUAGE plpgsql;
+    SQL
+
+    # Attach the trigger to the table
+    execute <<~SQL
+      CREATE TRIGGER enforce_relationships
+      BEFORE INSERT OR UPDATE ON relationships
+      FOR EACH ROW
+      EXECUTE FUNCTION validate_relationships();
+    SQL
+  end
+
+  def down
+    # Remove the trigger and function if rolling back
+    execute "DROP TRIGGER IF EXISTS enforce_relationships ON relationships;"
+    execute "DROP FUNCTION IF EXISTS validate_relationships();"
+  end
+end