fix: increase performance of outdated SDK query (#7226)

Joining might not always be the best solution. If a table contains too
much data, and you later run sorting on top of it, it will be slow.

In this case, we will first reduce the instances table to a minimal
version because instances usually share the same SDK versions. Only
after that, we join.

Based on some customer data, we reduced query time from 3000ms to 60ms.
However, this will vary based on the number of instances the customer
has.

src/lib/db/client-instance-store.ts

@@ -222,15 +222,22 @@ export default class ClientInstanceStore implements IClientInstanceStore {
         projectId: string,
     ): Promise<{ sdkVersion: string; applications: string[] }[]> {
         const rows = await this.db
+            .with(
+                'instances',
+                this.db
+                    .select('app_name', 'sdk_version')
+                    .distinct()
+                    .from('client_instances'),
+            )
             .select([
-                'ci.sdk_version as sdkVersion',
+                'i.sdk_version as sdkVersion',
                 this.db.raw('ARRAY_AGG(DISTINCT cme.app_name) as applications'),
             ])
             .from('client_metrics_env as cme')
             .leftJoin('features as f', 'f.name', 'cme.feature_name')
-            .leftJoin('client_instances as ci', 'ci.app_name', 'cme.app_name')
+            .leftJoin('instances as i', 'i.app_name', 'cme.app_name')
             .where('f.project', projectId)
-            .groupBy('ci.sdk_version');
+            .groupBy('i.sdk_version');
 
         return rows;
     }