mongodb/node-mongodb-native · error · MongoTailableCursorError

Tailable cursor does not support sorting

Error message

Tailable cursor does not support sorting

What it means

Thrown as MongoTailableCursorError by FindCursor.sort() when findOptions.tailable is true. Tailable cursors follow a capped collection in natural insertion order; applying a sort would defeat the tailing semantics and is unsupported by the server, so the driver rejects it client-side.

Source

Thrown at src/cursor/find_cursor.ts:419

   * }});
   * ```
   */
  project<T extends Document = Document>(value: Document): FindCursor<T> {
    this.throwIfInitialized();
    this.findOptions.projection = value;
    return this as unknown as FindCursor<T>;
  }

  /**
   * Sets the sort order of the cursor query.
   *
   * @param sort - The key or keys set for the sort.
   * @param direction - The direction of the sorting (1 or -1).
   */
  sort(sort: Sort | string, direction?: SortDirection): this {
    this.throwIfInitialized();
    if (this.findOptions.tailable) {
      throw new MongoTailableCursorError('Tailable cursor does not support sorting');
    }

    this.findOptions.sort = formatSort(sort, direction);
    return this;
  }

  /**
   * Allows disk use for blocking sort operations exceeding 100MB memory. (MongoDB 3.2 or higher)
   *
   * @remarks
   * {@link https://www.mongodb.com/docs/manual/reference/command/find/#find-cmd-allowdiskuse | find command allowDiskUse documentation}
   */
  allowDiskUse(allow = true): this {
    this.throwIfInitialized();

    if (!this.findOptions.sort) {
      throw new MongoInvalidArgumentError('Option "allowDiskUse" requires a sort specification');
    }

View on GitHub (pinned to 3366c21a63)

Solutions

1. Remove the .sort() call on tailable cursors — they iterate in natural order
2. If you need ordering, query a non-capped collection or read from the capped collection without tailable and sort the result set
3. Drop the tailable option if sorted results are required

Example fix

// before
coll.find({}, { tailable: true, awaitData: true }).sort({ ts: -1 });
// after
coll.find({}, { tailable: true, awaitData: true });

function sortSafe(cursor, sort, direction) {
  if (cursor.findOptions?.tailable) {
    throw new Error('cannot sort a tailable cursor; remove tailable or sort');
  }
  return cursor.sort(sort, direction);
}

When it happens

Trigger: coll.find({}, { tailable: true }).sort({ ts: -1 }) or coll.find({}, { tailable: true, awaitData: true }).sort(...). Also when tailable is inferred for a change stream's underlying cursor in custom code.

Common situations: Building a tailing listener on the oplog/capped collection and adding sort(); converting a normal find to tailable without removing the sort call.

Related errors

• Tailable cursor does not support limit
• Tailable cursor does not support skip
• Argument for maxAwaitTimeMS must be a number
• Option "allowDiskUse" requires a sort specification
• Invalid sort direction: ${JSON.stringify(direction)}

AI-assisted analysis of mongodb/node-mongodb-native@3366c21a63 (2026-08-04). Data as JSON: /data/errors/3d8513b54a97264b.json. Report an issue: GitHub.