Optimize conversation open performance

ts/sql/Server.ts

@@ -2653,7 +2653,7 @@ function getOldestMessageForConversation(
   const row = db
     .prepare<Query>(
       `
-      SELECT * FROM messages WHERE
+      SELECT received_at, sent_at, id FROM messages WHERE
         conversationId = $conversationId AND
         isStory IS 0 AND
         (${_storyIdPredicate(storyId, includeStoryReplies)})
@@ -2686,7 +2686,7 @@ function getNewestMessageForConversation(
   const row = db
     .prepare<Query>(
       `
-      SELECT * FROM messages WHERE
+      SELECT received_at, sent_at, id FROM messages WHERE
         conversationId = $conversationId AND
         isStory IS 0 AND
         (${_storyIdPredicate(storyId, includeStoryReplies)})
@@ -2750,35 +2750,29 @@ function getLastConversationPreview({
 }): MessageType | undefined {
   type Row = Readonly<{
     json: string;
-    received_at: number;
-    sent_at: number;
   }>;
 
   const db = getInstance();
 
-  const queryTemplate = (extraClause: string): string => {
-    return `
-      SELECT json, received_at, sent_at FROM messages
-      INDEXED BY messages_preview
-      WHERE
-        conversationId IS $conversationId AND
-        shouldAffectPreview IS 1 AND
-        isGroupLeaveEventFromOther IS 0 AND
-        ${includeStoryReplies ? '' : 'storyId IS NULL AND'}
-        ${extraClause}
-      ORDER BY received_at DESC, sent_at DESC
-      LIMIT 1
-    `;
-  };
+  const index = includeStoryReplies
+    ? 'messages_preview'
+    : 'messages_preview_without_story';
 
   const row: Row | undefined = prepare(
     db,
     `
-      SELECT * FROM (${queryTemplate('expiresAt IS NULL')})
-      UNION ALL
-      SELECT * FROM (${queryTemplate('expiresAt > $now')})
-      ORDER BY received_at DESC, sent_at DESC
-      LIMIT 1;
+      SELECT json FROM (
+        SELECT json, expiresAt FROM messages
+        INDEXED BY ${index}
+        WHERE
+          conversationId IS $conversationId AND
+          shouldAffectPreview IS 1 AND
+          isGroupLeaveEventFromOther IS 0
+          ${includeStoryReplies ? '' : 'AND storyId IS NULL'}
+        ORDER BY received_at DESC, sent_at DESC
+      )
+      WHERE likely(expiresAt > $now)
+      LIMIT 1
     `
   ).get({
     conversationId,
@@ -2824,7 +2818,7 @@ async function getLastConversationMessage({
   const row = db
     .prepare<Query>(
       `
-      SELECT * FROM messages WHERE
+      SELECT json FROM messages WHERE
         conversationId = $conversationId
       ORDER BY received_at DESC, sent_at DESC
       LIMIT 1;
@@ -2855,7 +2849,7 @@ function getOldestUnseenMessageForConversation(
   const row = db
     .prepare<Query>(
       `
-      SELECT * FROM messages WHERE
+      SELECT received_at, sent_at, id FROM messages WHERE
         conversationId = $conversationId AND
         seenStatus = ${SeenStatus.Unseen} AND
         isStory IS 0 AND
@@ -3130,7 +3124,6 @@ async function getExpiredMessages(): Promise<Array<MessageType>> {
     .prepare<Query>(
       `
       SELECT json FROM messages WHERE
-        expiresAt IS NOT NULL AND
         expiresAt <= $now
       ORDER BY expiresAt ASC;
       `
@@ -3181,6 +3174,10 @@ async function getSoonestMessageExpiry(): Promise<undefined | number> {
     .pluck(true)
     .get();
 
+  if (result != null && result >= Number.MAX_SAFE_INTEGER) {
+    return undefined;
+  }
+
   return result || undefined;
 }
 

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!');
+}

ts/sql/migrations/index.ts

@@ -51,6 +51,7 @@ import updateToSchemaVersion72 from './72-optimize-call-id-message-lookup';
 import updateToSchemaVersion73 from './73-remove-phone-number-discovery';
 import updateToSchemaVersion74 from './74-optimize-convo-open';
 import updateToSchemaVersion75 from './75-signal-tokenizer';
+import updateToSchemaVersion76 from './76-optimize-convo-open-2';
 
 function updateToSchemaVersion1(
   currentVersion: number,
@@ -1971,6 +1972,7 @@ export const SCHEMA_VERSIONS = [
   updateToSchemaVersion73,
   updateToSchemaVersion74,
   updateToSchemaVersion75,
+  updateToSchemaVersion76,
 ];
 
 export function updateSchema(db: Database, logger: LoggerType): void {