refactor: daily active users remove FK and update index (#8025)

* refactor: daily active users remove FK and update index

* chore: update code

* chore: remove comments

Author: darcyYe

packages/schemas/alterations/next-1764580455-remove-daily-active-users-foreign-key.ts

@@ -0,0 +1,69 @@
+import { sql } from '@silverhand/slonik';
+
+import type { AlterationScript } from '../lib/types/alteration.js';
+
+/**
+ * Remove foreign key constraint from daily_active_users table to allow
+ * historical billing data to persist even after tenant deletion.
+ * This supports the MAU-based billing system requirements.
+ *
+ * Index optimizations:
+ * 1. Removes redundant (tenant_id, id) index (id is already primary key)
+ * 2. Adds optimized index (tenant_id, date, user_id) for aggregation queries
+ * 3. Replaces problematic partial index with BRIN index
+ */
+
+const alteration: AlterationScript = {
+  up: async (pool) => {
+    // Drop the existing foreign key constraint
+    await pool.query(sql`
+      alter table daily_active_users
+      drop constraint if exists daily_active_users_tenant_id_fkey
+    `);
+
+    // Remove the redundant (tenant_id, id) index since id is already primary key
+    await pool.query(sql`
+      drop index if exists daily_active_users__id
+    `);
+
+    // Add optimized index for aggregation queries with better write performance
+    await pool.query(sql`
+      create index daily_active_users__tenant_date_user
+      on daily_active_users (tenant_id, date, user_id)
+    `);
+
+    // Add BRIN index for time-series date range queries
+    // Optimized for sequential data insertion and range scans (date >= ?)
+    await pool.query(sql`
+      create index daily_active_users__date_brin
+      on daily_active_users using brin (date)
+    `);
+  },
+
+  down: async (pool) => {
+    // Drop the new indexes we created
+    await pool.query(sql`
+      drop index if exists daily_active_users__date_brin
+    `);
+
+    await pool.query(sql`
+      drop index if exists daily_active_users__tenant_date_user
+    `);
+
+    // Recreate the original redundant index
+    await pool.query(sql`
+      create index daily_active_users__id
+      on daily_active_users (tenant_id, id)
+    `);
+
+    // Recreate the foreign key constraint
+    await pool.query(sql`
+      alter table daily_active_users
+      add constraint daily_active_users_tenant_id_fkey
+      foreign key (tenant_id) references tenants(id)
+      on update cascade on delete cascade
+    `);
+  },
+};
+
+export default alteration;

packages/schemas/tables/daily_active_users.sql

@@ -1,16 +1,21 @@
 create table daily_active_users (
   id varchar(21) not null,
-  tenant_id varchar(21) not null
-    references tenants (id) on update cascade on delete cascade,
+  tenant_id varchar(21) not null,
   user_id varchar(21) not null,
   date timestamptz not null default (now()),
   primary key (id),
   constraint daily_active_users__user_id_date
     unique (user_id, date)
 );
 
-create index daily_active_users__id
-  on daily_active_users (tenant_id, id);
+-- Optimized index for aggregation queries with better write performance
+create index daily_active_users__tenant_date_user
+  on daily_active_users (tenant_id, date, user_id);
+
+-- BRIN index for time-series date range queries
+-- Optimized for sequential data insertion and range scans (date >= ?)
+create index daily_active_users__date_brin
+  on daily_active_users using brin (date);
 
 create index daily_active_users__date
   on daily_active_users (tenant_id, date);