As discussed with @kitaisreal 
{
    if (&other == this)
        return *this;
    columns = other.columns;
    secondary_indices = other.secondary_indices;
    constraints = other.constraints;
    projections = other.projections.clone();
    partition_key = other.partition_key;
    primary_key = other.primary_key;
    sorting_key = other.sorting_key;
    sampling_key = other.sampling_key;
    column_ttls_by_name = other.column_ttls_by_name;
    table_ttl = other.table_ttl;
    if (other.settings_changes)
        settings_changes = other.settings_changes->clone();
    else
        settings_changes.reset();
    select = other.select;
    comment = other.comment;
    return *this;
}
void StorageInMemoryMetadata::setComment(const String & comment_)