Reenable FTS optimization

ts/sql/Server.ts

@@ -93,6 +93,7 @@ import type {
   DeleteSentProtoRecipientResultType,
   EditedMessageType,
   EmojiType,
+  FTSOptimizationStateType,
   GetAllStoriesResultType,
   GetConversationRangeCenteredOnMessageResultType,
   GetKnownMessageAttachmentsResultType,
@@ -402,6 +403,8 @@ const dataInterface: ServerInterface = {
 
   getStatisticsForLogging,
 
+  optimizeFTS,
+
   // Server-only
 
   initialize,
@@ -2219,6 +2222,7 @@ async function _removeAllMessages(): Promise<void> {
   const db = getInstance();
   db.exec(`
     DELETE FROM messages;
+    INSERT INTO messages_fts(messages_fts) VALUES('optimize');
   `);
 }
 
@@ -5544,6 +5548,8 @@ async function removeAll(): Promise<void> {
       DELETE FROM unprocessed;
       DELETE FROM uninstalled_sticker_packs;
 
+      INSERT INTO messages_fts(messages_fts) VALUES('optimize');
+
       --- Re-create the messages delete trigger
       --- See migration 45
       CREATE TRIGGER messages_on_delete AFTER DELETE ON messages BEGIN
@@ -6127,6 +6133,48 @@ async function removeKnownDraftAttachments(
   return Object.keys(lookup);
 }
 
+const OPTIMIZE_FTS_PAGE_COUNT = 64;
+
+// This query is incremental. It gets the `state` from the return value of
+// previous `optimizeFTS` call. When `state.done` is `true` - optimization is
+// complete.
+async function optimizeFTS(
+  state?: FTSOptimizationStateType
+): Promise<FTSOptimizationStateType | undefined> {
+  // See https://www.sqlite.org/fts5.html#the_merge_command
+  let pageCount = OPTIMIZE_FTS_PAGE_COUNT;
+  if (state === undefined) {
+    pageCount = -pageCount;
+  }
+  const db = getInstance();
+  const getChanges = prepare(db, 'SELECT total_changes() as changes;', {
+    pluck: true,
+  });
+
+  const changeDifference = db.transaction(() => {
+    const before: number = getChanges.get({});
+
+    prepare(
+      db,
+      `
+        INSERT INTO messages_fts(messages_fts, rank) VALUES ('merge', $pageCount);
+      `
+    ).run({ pageCount });
+
+    const after: number = getChanges.get({});
+
+    return after - before;
+  })();
+
+  const nextSteps = (state?.steps ?? 0) + 1;
+
+  // From documentation:
+  // "If the difference is less than 2, then the 'merge' command was a no-op"
+  const done = changeDifference < 2;
+
+  return { steps: nextSteps, done };
+}
+
 async function getJobsInQueue(queueType: string): Promise<Array<StoredJob>> {
   const db = getInstance();
   return getJobsInQueueSync(db, queueType);