perf(database): drop unused TaskRun(scheduleId, createdAt) index

The schedule list view reads from ClickHouse, so this composite
index served no Prisma query while still being maintained on every
TaskRun INSERT/UPDATE.

Author: ericallam

.server-changes/drop-taskrun-scheduleid-createdat-idx.md

@@ -0,0 +1,6 @@
+---
+area: webapp
+type: improvement
+---
+
+Reduce primary database write load on `TaskRun` by dropping an unused composite index on `(scheduleId, createdAt)`. The schedule list view reads from ClickHouse, so this Postgres index served no Prisma query while still being maintained on every `TaskRun` INSERT/UPDATE.

internal-packages/database/prisma/migrations/20260522150206_drop_task_run_schedule_id_created_at_idx/migration.sql

@@ -0,0 +1,2 @@
+-- DropIndex
+DROP INDEX CONCURRENTLY IF EXISTS "public"."TaskRun_scheduleId_createdAt_idx";

internal-packages/database/prisma/schema.prisma

@@ -1084,8 +1084,6 @@ model TaskRun {
   // Run page inspector
   @@index([spanId])
   @@index([parentSpanId])
-  // Schedule list page
-  @@index([scheduleId, createdAt(sort: Desc)])
   // Finding runs in a batch
   @@index([runTags(ops: ArrayOps)], type: Gin)
   @@index([runtimeEnvironmentId, batchId])