feat: add flow_id index in executions

packages/backend/src/db/migrations/20231025101146_add_flow_id_index_in_executions.ts

@@ -0,0 +1,13 @@
+import { Knex } from 'knex';
+
+export async function up(knex: Knex): Promise<void> {
+  await knex.schema.table('executions', (table) => {
+    table.index('flow_id');
+  });
+}
+
+export async function down(knex: Knex): Promise<void> {
+  await knex.schema.table('executions', (table) => {
+    table.dropIndex('flow_id');
+  });
+}