Optimize conversation open performance

ts/sql/migrations/76-optimize-convo-open-2.ts

@@ -0,0 +1,59 @@
+// Copyright 2023 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import type { Database } from '@signalapp/better-sqlite3';
+
+import type { LoggerType } from '../../types/Logging';
+
+export default function updateToSchemaVersion76(
+  currentVersion: number,
+  db: Database,
+  logger: LoggerType
+): void {
+  if (currentVersion >= 76) {
+    return;
+  }
+
+  db.transaction(() => {
+    db.exec(
+      `
+      -- Re-created below
+      DROP INDEX IF EXISTS message_expires_at;
+      DROP INDEX IF EXISTS messages_preview;
+
+      -- Create non-null expiresAt column
+      ALTER TABLE messages
+        DROP COLUMN expiresAt;
+
+      ALTER TABLE messages
+        ADD COLUMN
+        expiresAt INT
+        GENERATED ALWAYS
+        AS (ifnull(
+          expirationStartTimestamp + (expireTimer * 1000),
+          ${Number.MAX_SAFE_INTEGER}
+        ));
+
+      -- Re-create indexes
+      -- Note the "s" at the end of "messages"
+      CREATE INDEX messages_expires_at ON messages (
+        expiresAt
+      );
+
+      -- Note that expiresAt is intentionally dropped from the index since
+      -- expiresAt > $now is likely to be true so we just try selecting it
+      -- *after* ordering by received_at/sent_at.
+      CREATE INDEX messages_preview ON messages
+        (conversationId, shouldAffectPreview, isGroupLeaveEventFromOther,
+         received_at, sent_at);
+      CREATE INDEX messages_preview_without_story ON messages
+        (conversationId, shouldAffectPreview, isGroupLeaveEventFromOther,
+         received_at, sent_at) WHERE storyId IS NULL;
+      `
+    );
+
+    db.pragma('user_version = 76');
+  })();
+
+  logger.info('updateToSchemaVersion76: success!');
+}