From fb8d0fc19c27ff860bdefb7dcfe69eae546f837c Mon Sep 17 00:00:00 2001
From: Otavio Salvador <otavio@ossystems.com.br>
Date: Tue, 13 Oct 2026 17:19:00 -0300
Subject: [PATCH] fix(server): collect SQLite planner statistics when the
 database opens (#18471)

---
 apps/server/src/persistence/Sqlite.test.ts | 30 ++++++++++++++++++++++
 apps/server/src/persistence/Sqlite.ts      |  4 +++
 2 files changed, 34 insertions(+)

diff --git a/apps/server/src/persistence/Sqlite.test.ts b/apps/server/src/persistence/Sqlite.test.ts
index 1bdacd0d13d7814905f2e00b736a6191d02becad..666e14d3a5cc69f39b3ceae7b54609df9bfe717e 100644
--- a/apps/server/src/persistence/Sqlite.test.ts
+++ b/apps/server/src/persistence/Sqlite.test.ts
@@ -84,6 +84,36 @@ it.effect("shrinks the WAL file back to the size limit after a large write", ()
   );
 });
 
+it.effect("collects planner statistics for an existing database on open", () => {
+  const tempDir = NodeFS.mkdtempSync(NodePath.join(NodeOS.tmpdir(), "t3-sqlite-stats-"));
+  const dbPath = NodePath.join(tempDir, "state.sqlite");
+  const persistence = () =>
+    SqlitePersistence.layerFromPath(dbPath).pipe(Layer.provide(NodeServices.layer));
+
+  return Effect.gen(function* () {
+    yield* Effect.gen(function* () {
+      const sql = yield* SqlClient.SqlClient;
+      yield* sql`CREATE TABLE stats_probe(id INTEGER PRIMARY KEY, thread_id TEXT NOT NULL)`;
+      yield* sql`CREATE INDEX stats_probe_thread_idx ON stats_probe(thread_id)`;
+      yield* sql`
+        WITH RECURSIVE n(i) AS (SELECT 1 UNION ALL SELECT i + 1 FROM n WHERE i < 1000)
+        INSERT INTO stats_probe(thread_id) SELECT 'thread-' || (i % 10) FROM n
+      `;
+    }).pipe(Effect.provide(persistence()));
+
+    // A database written before statistics existed gets them on the next open.
+    yield* Effect.gen(function* () {
+      const sql = yield* SqlClient.SqlClient;
+      const rows = yield* sql<{ readonly stat: string }>`
+        SELECT stat FROM sqlite_stat1 WHERE idx = 'stats_probe_thread_idx'
+      `;
+      assert.deepEqual([...rows], [{ stat: "1000 100" }]);
+    }).pipe(Effect.provide(persistence()));
+  }).pipe(
+    Effect.ensuring(Effect.sync(() => NodeFS.rmSync(tempDir, { recursive: true, force: true }))),
+  );
+});
+
 it.effect("applies busy_timeout in the shared persistence setup", () =>
   Effect.gen(function* () {
     const sql = yield* SqlClient.SqlClient;
diff --git a/apps/server/src/persistence/Sqlite.ts b/apps/server/src/persistence/Sqlite.ts
index 0f248b5a2387776659f95aa20fdacc8a893a51b6..2ea5199b28337748918e1e5fd08d0bf52204994f 100644
--- a/apps/server/src/persistence/Sqlite.ts
+++ b/apps/server/src/persistence/Sqlite.ts
@@ -23,6 +23,10 @@ const layerSetup = Layer.effectDiscard(
     // largest size until the last connection closes.
     yield* sql.unsafe(`PRAGMA journal_size_limit = ${WAL_SIZE_LIMIT_BYTES};`);
     yield* runMigrations();
+    // Without sqlite_stat1 the planner guesses at index selectivity. 0x10012
+    // analyzes tables whose indexes lack stats or whose row count changed 10x,
+    // under a temporary analysis_limit. Otherwise it only checks table sizes.
+    yield* sql`PRAGMA optimize = 0x10012;`;
   }),
 );
 
-- 
2.54.0