fix: make project ui query optimized (#8961)

From 13 seconds to 0.1 seconds.

1. Joining 1 million events to projects/features is slow. **Solved by
using CTE.**
2. Running grouping on 1 million rows is slow. **Solved by adding
index.**

src/lib/features/project/project-read-model.test.ts

@@ -46,6 +46,7 @@ afterAll(async () => {
 beforeEach(async () => {
     await projectStore.deleteAll();
     await flagStore.deleteAll();
+    await eventStore.deleteAll();
 });
 
 test("it doesn't count flags multiple times when they have multiple events associated with them", async () => {

src/lib/features/project/project-read-model.ts

@@ -83,7 +83,14 @@ export class ProjectReadModel implements IProjectReadModel {
         userId?: number,
     ): Promise<ProjectForUi[]> {
         const projectTimer = this.timer('getProjectsForAdminUi');
-        let projects = this.db(TABLE)
+        let projects = this.db
+            .with('latest_events', (qb) => {
+                qb.select('project', 'feature_name')
+                    .max('created_at as last_updated')
+                    .whereNotNull('feature_name')
+                    .from('events')
+                    .groupBy('project', 'feature_name');
+            })
             .leftJoin('features', 'features.project', 'projects.id')
             .leftJoin(
                 'last_seen_at_metrics',
@@ -95,13 +102,14 @@ export class ProjectReadModel implements IProjectReadModel {
                 'project_settings.project',
                 'projects.id',
             )
-            .leftJoin('events', (join) => {
-                join.on('events.feature_name', '=', 'features.name').andOn(
-                    'events.project',
+            .leftJoin('latest_events', (join) => {
+                join.on(
+                    'latest_events.feature_name',
                     '=',
-                    'projects.id',
-                );
+                    'features.name',
+                ).andOn('latest_events.project', '=', 'projects.id');
             })
+            .from(TABLE)
             .orderBy('projects.name', 'asc');
 
         if (query?.archived === true) {
@@ -122,7 +130,7 @@ export class ProjectReadModel implements IProjectReadModel {
                 'projects.id, projects.name, projects.description, projects.health, projects.created_at, ' +
                     'count(DISTINCT features.name) FILTER (WHERE features.archived_at is null) AS number_of_features, ' +
                     'MAX(last_seen_at_metrics.last_seen_at) AS last_usage, ' +
-                    'MAX(events.created_at) AS last_updated',
+                    'MAX(latest_events.last_updated) AS last_updated',
             ),
             'project_settings.project_mode',
             'projects.archived_at',

src/migrations/20241211143944-events-index-project-feature-created.js

@@ -0,0 +1,20 @@
+'use strict';
+
+exports.up = function (db, callback) {
+    db.runSql(
+        `
+          CREATE INDEX idx_events_project_feature_created
+            ON events (project, feature_name, created_at DESC);
+        `,
+        callback,
+    );
+};
+
+exports.down = function (db, callback) {
+    db.runSql(
+        `
+           DROP INDEX idx_events_project_feature_created;
+        `,
+        callback,
+    );
+};