Method getMore

src/cursor/find_cursor.ts:101–145

@internal

()

  /** @internal */
  override async getMore(): Promise<CursorResponse> {
    const numReturned = this.numReturned;
    const limit = this.findOptions.limit ?? Infinity;
    const remaining = limit - numReturned;

    if (numReturned === limit && !this.id?.isZero()) {
      // this is an optimization for the special case of a limit for a find command to avoid an
      // extra getMore when the limit has been reached and the limit is a multiple of the batchSize.
      // This is a consequence of the new query engine in 5.0 having no knowledge of the limit as it
      // produces results for the find command.  Once a batch is filled up, it is returned and only
      // on the subsequent getMore will the query framework consider the limit, determine the cursor
      // is exhausted and return a cursorId of zero.
      // instead, if we determine there are no more documents to request from the server, we preemptively
      // close the cursor
      try {
        await this.close();
      } catch (error) {
        squashError(error);
      }
      return CursorResponse.emptyGetMore;
    }

    // TODO(DRIVERS-1448): Remove logic to enforce `limit` in the driver
    let cleanup: () => void = noop;
    const { batchSize } = this.cursorOptions;
    if (batchSize != null && batchSize > remaining) {
      this.cursorOptions.batchSize = remaining;

      // After executing the final getMore, re-assign the batchSize back to its original value so that
      // if the cursor is rewound and executed, the batchSize is still correct.
      cleanup = () => {
        this.cursorOptions.batchSize = batchSize;
      };
    }

    try {
      const response = await super.getMore();

      this.numReturned = this.numReturned + response.batchSize;

      return response;
    } finally {
      cleanup?.();
    }
  }

  /**
   * Get the count of documents for this cursor