Fix messages_preview index

ts/sql/Server.ts

@@ -2541,10 +2541,8 @@ function getLastConversationActivity({
 }
 function getLastConversationPreview({
   conversationId,
-  ourUuid,
 }: {
   conversationId: string;
-  ourUuid: UUIDStringType;
 }): MessageType | undefined {
   const db = getInstance();
   const row = prepare(
@@ -2565,7 +2563,6 @@ function getLastConversationPreview({
       `
   ).get({
     conversationId,
-    ourUuid,
     now: Date.now(),
   });
 
@@ -2591,10 +2588,7 @@ async function getLastConversationMessages({
         conversationId,
         ourUuid,
       }),
-      preview: getLastConversationPreview({
+      preview: getLastConversationPreview({ conversationId }),
-        conversationId,
-        ourUuid,
-      }),
       hasUserInitiatedMessages: hasUserInitiatedMessages(conversationId),
     };
   })();

ts/sql/migrations/49-fix-preview-index.ts

@@ -0,0 +1,33 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import type { Database } from 'better-sqlite3';
+
+import type { LoggerType } from '../../types/Logging';
+
+export default function updateToSchemaVersion49(
+  currentVersion: number,
+  db: Database,
+  logger: LoggerType
+): void {
+  if (currentVersion >= 49) {
+    return;
+  }
+
+  db.transaction(() => {
+    db.exec(
+      `
+      DROP INDEX messages_preview;
+
+      -- Note the omitted 'expiresAt' column in the index. If it is present
+      -- sqlite can't ORDER BY received_at, sent_at using this index.
+      CREATE INDEX messages_preview ON messages
+        (conversationId, shouldAffectPreview, isGroupLeaveEventFromOther, received_at, sent_at);
+      `
+    );
+
+    db.pragma('user_version = 49');
+  })();
+
+  logger.info('updateToSchemaVersion49: success!');
+}

ts/sql/migrations/index.ts

@@ -24,6 +24,7 @@ import updateToSchemaVersion45 from './45-stories';
 import updateToSchemaVersion46 from './46-optimize-stories';
 import updateToSchemaVersion47 from './47-further-optimize';
 import updateToSchemaVersion48 from './48-fix-user-initiated-index';
+import updateToSchemaVersion49 from './49-fix-preview-index';
 
 function updateToSchemaVersion1(
   currentVersion: number,
@@ -1911,6 +1912,7 @@ export const SCHEMA_VERSIONS = [
   updateToSchemaVersion46,
   updateToSchemaVersion47,
   updateToSchemaVersion48,
+  updateToSchemaVersion49,
 ];
 
 export function updateSchema(db: Database, logger: LoggerType): void {

ts/test-node/sql_migrations_test.ts

@@ -1292,4 +1292,36 @@ describe('SQL migrations test', () => {
       );
     });
   });
+
+  describe('updateToSchemaVersion49', () => {
+    it('creates usable index for messages preview', () => {
+      updateToVersion(49);
+
+      const details = db
+        .prepare(
+          `
+        EXPLAIN QUERY PLAN
+        SELECT json FROM messages
+        WHERE
+          conversationId = 'convo' AND
+          shouldAffectPreview IS 1 AND
+          isGroupLeaveEventFromOther IS 0 AND
+          (
+            expiresAt IS NULL
+            OR
+            expiresAt > 123
+          )
+        ORDER BY received_at DESC, sent_at DESC
+        LIMIT 1;
+        `
+        )
+        .all()
+        .map(({ detail }) => detail)
+        .join('\n');
+
+      assert.include(details, 'USING INDEX messages_preview');
+      assert.notInclude(details, 'TEMP B-TREE');
+      assert.notInclude(details, 'SCAN');
+    });
+  });
 });