For some reasons when we delete a MergeTree Part in atomic way something may go wrong - and leave the `delete_tmp_*` folder or it's part on disk. This may lead to a disk space consumption over time.

It's suggested to delete this folders at least at server start-up. Current solution with `clearOldTemporaryDirectories()` doesn't work because this method is called periodically from a thread without any locks or advisory on folders - it may cause the race conditions.
{
    return getContext()->getStoragePolicy(getSettings()->storage_policy);
}
bool MergeTreeData::supportsFinal() const
{
    return merging_params.mode == MergingParams::Collapsing
        || merging_params.mode == MergingParams::Summing
        || merging_params.mode == MergingParams::Aggregating
        || merging_params.mode == MergingParams::Replacing
        || merging_params.mode == MergingParams::Graphite
        || merging_params.mode == MergingParams::VersionedCollapsing;
}
static void checkKeyExpression(const ExpressionActions & expr, const Block & sample_block, const String & key_name, bool allow_nullable_key)