replace the slow postgres trigger function for updating label names

packages/db/migrations/0158.do.create_label_names_update_trigger.sql

@@ -0,0 +1,30 @@
+-- Type: DO
+-- Name: create_label_names_update_trigger
+-- Description: Create label_names_update trigger in library_item table
+
+BEGIN;
+
+CREATE OR REPLACE FUNCTION update_label_names()
+RETURNS TRIGGER AS $$
+BEGIN
+    UPDATE omnivore.library_item
+    SET label_names = array_replace(label_names, OLD.name, NEW.name)
+    WHERE user_id = OLD.user_id AND OLD.name = ANY(label_names);
+
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+-- triggers when label name is updated
+CREATE TRIGGER label_names_update
+AFTER UPDATE ON omnivore.labels
+FOR EACH ROW
+WHEN (OLD.name <> NEW.name)
+EXECUTE FUNCTION update_label_names();
+
+-- remove old trigger which is too slow
+DROP TRIGGER IF EXISTS entity_labels_update ON omnivore.labels;
+
+DROP FUNCTION IF EXISTS omnivore.update_entity_labels();
+
+COMMIT;

packages/db/migrations/0158.undo.create_label_names_update_trigger.sql

@@ -0,0 +1,30 @@
+-- Type: UNDO
+-- Name: create_label_names_update_trigger
+-- Description: Create label_names_update trigger in library_item table
+
+BEGIN;
+
+CREATE OR REPLACE FUNCTION update_entity_labels()
+RETURNS trigger AS $$
+BEGIN
+    -- update entity_labels table to trigger update on library_item table
+    UPDATE omnivore.entity_labels
+    SET label_id = NEW.id
+    WHERE label_id = OLD.id;
+
+    return NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+-- triggers when label name is updated
+CREATE TRIGGER entity_labels_update
+AFTER UPDATE ON omnivore.labels
+FOR EACH ROW
+WHEN (OLD.name <> NEW.name)
+EXECUTE FUNCTION update_entity_labels();
+
+DROP TRIGGER IF EXISTS label_names_update ON omnivore.labels;
+
+DROP FUNCTION IF EXISTS omnivore.update_label_names();
+
+COMMIT;