/**
 * Returns the largest _id value in the collection.
 */
Value findHighestInsertedId(OperationContext* opCtx, const CollectionPtr& collection);

/**
 * Returns a batch of documents totaling in size to at most batchSizeLimitBytes.
 */
std::vector<InsertStatement> fillBatchForInsert(Pipeline& pipeline, int batchSizeLimitBytes);

/**
 * Atomically inserts a batch of documents in a single storage transaction. Returns the number of
 * bytes inserted.
 *
 * Throws NamespaceNotFound if the collection doesn't already exist.
 */
int insertBatch(OperationContext* opCtx,
                const NamespaceString& nss,
                std::vector<InsertStatement>& batch);

class ReshardingCollectionCloner {
public:
    ...

    /**
     * Schedules work to repeatedly fetch and insert batches of documents.
     *
     * Returns a future that becomes ready when either:
     *   (a) all documents have been fetched and inserted, or
     *   (b) the cancellation token was canceled due to a stepdown or abort.
     */
    SemiFuture<void> run(std::shared_ptr<executor::TaskExecutor> executor,
                         CancelationToken cancelToken);

    /**
     * Fetches and inserts a single batch of documents.
     *
     * Returns true if there are more documents to be fetched and inserted, and returns false
     * otherwise.
     */
    bool doOneBatch(OperationContext* opCtx, Pipeline& pipeline);

private:
    std::unique_ptr<Pipeline, PipelineDeleter> _restartPipeline(OperationContext* opCtx);

    ...
};