If they are defined, they can override table-level settings.
{
    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)