perf(server): the shell read no longer sorts every run of every thread

apps/server/src/orchestration-v2/ProjectionStore.test.ts

@@ -5206,6 +5206,32 @@ it.layer(layerTest)("ProjectionStoreV2", (it) => {
     }),
   );
 
+  it.effect("reads a thread's last executed run through the last executed run index", () =>
+    Effect.gen(function* () {
+      const projectionStore = yield* ProjectionStore.ProjectionStoreV2;
+      const sql = yield* SqlClient.SqlClient;
+      const { projectId } = yield* assertProjectScopedShells("sql-shell-last-executed-index");
+      const { statements, tracer } = traceSqlStatements();
+      yield* projectionStore
+        .getShellSnapshot({ projectId, location: "active" })
+        .pipe(Effect.withTracer(tracer));
+
+      const threadQuery = statements.find((statement) =>
+        statement.includes("AS latest_run_stop_requested"),
+      );
+      assert.isDefined(threadQuery);
+      const plan = (yield* sql.unsafe<{ readonly detail: string }>(
+        `EXPLAIN QUERY PLAN ${threadQuery}`,
+      )).map((row) => row.detail);
+      const lastExecutedIndex = plan.findIndex((detail) =>
+        detail.includes("orchestration_v2_projection_runs_last_executed_idx"),
+      );
+      assert.notStrictEqual(lastExecutedIndex, -1);
+      // The lookup that follows the search is the sort it no longer needs.
+      assert.notInclude(plan[lastExecutedIndex + 1] ?? "", "USE TEMP B-TREE");
+    }),
+  );
+
   it.effect("reads a run's turn-start items by thread and run, not by walking thread history", () =>
     Effect.gen(function* () {
       const projectionStore = yield* ProjectionStore.ProjectionStoreV2;

apps/server/src/persistence/Migrations.ts

@@ -85,6 +85,7 @@ import Migration0079 from "./Migrations/079_DelegatedRecoveryIndexes.ts";
 import Migration0080 from "./Migrations/080_ScheduledTaskThreadMode.ts";
 import Migration0081 from "./Migrations/081_ProjectionMessageSearchText.ts";
 import Migration0082 from "./Migrations/082_TurnItemConversationIndex.ts";
+import Migration0083 from "./Migrations/083_LastExecutedRunIndex.ts";
 
 const migrationEntries = [
   [1, "OrchestrationEvents", Migration0001],
@@ -170,6 +171,7 @@ const migrationEntries = [
   [80, "ScheduledTaskThreadMode", Migration0080],
   [81, "ProjectionMessageSearchText", Migration0081],
   [82, "TurnItemConversationIndex", Migration0082],
+  [83, "LastExecutedRunIndex", Migration0083],
 ] as const;
 
 export const migrationManifest = migrationEntries.map(([id, name]) => [id, name] as const);

apps/server/src/persistence/Migrations/083_LastExecutedRunIndex.ts

@@ -0,0 +1,18 @@
+import * as Effect from "effect/Effect";
+import * as SqlClient from "effect/sql/SqlClient";
+
+export default Effect.gen(function* () {
+  const sql = yield* SqlClient.SqlClient;
+
+  // The shell's last executed run lookup sorts every run of the thread. This index carries
+  // that order and the same predicate the lookup filters on. A database that already has
+  // the index keeps it, so a hand-applied one does not fail the migration.
+  yield* sql`
+    CREATE INDEX IF NOT EXISTS orchestration_v2_projection_runs_last_executed_idx
+    ON orchestration_v2_projection_runs(
+      thread_id, (completed_at IS NULL) DESC, completed_at DESC, ordinal DESC, run_id DESC
+    )
+    WHERE status <> 'queued'
+      AND NOT (status = 'cancelled' AND json_extract(payload_json, '$.startedAt') IS NULL)
+  `;
+});

apps/server/src/persistence/reconcileV2PreviewMigration.test.ts

@@ -62,6 +62,7 @@ describe("V2 preview upgrade", () => {
         [80, "ScheduledTaskThreadMode"],
         [81, "ProjectionMessageSearchText"],
         [82, "TurnItemConversationIndex"],
+        [83, "LastExecutedRunIndex"],
       ]);
       assert.deepStrictEqual(yield* runMigrations(), []);
       assert.deepStrictEqual(yield* sql`SELECT * FROM orchestration_v2_legacy_imports`, imports);
@@ -167,6 +168,7 @@ describe("V2 preview upgrade", () => {
         [80, "ScheduledTaskThreadMode"],
         [81, "ProjectionMessageSearchText"],
         [82, "TurnItemConversationIndex"],
+        [83, "LastExecutedRunIndex"],
       ]);
     }).pipe(Effect.provide(NodeSqliteClient.layer({ filename: ":memory:" }))),
   );