And waits for them. That's pointless.
const FutureMergedMutatedPart & future_part,
    const StorageMetadataPtr & metadata_snapshot,
    const MutationCommands & commands,
    MergeListEntry & merge_entry,
    time_t time_of_mutation,
    ContextPtr context,
    const ReservationPtr & space_reservation,
    TableLockHolder & holder)
{
    checkOperationIsNotCanceled(merge_entry);