/// <inheritdoc/>
        protected override Provider VisitSelect(SelectProvider provider)
        {
            OnRecursionEntrance(provider);
            var source        = VisitCompilable(provider.Source);
            var columnIndexes = (int[])OnRecursionExit(provider);

            if (source == provider.Source)
            {
                return(provider);
            }
            return(new SelectProvider(source, columnIndexes ?? provider.ColumnIndexes));
        }
 /// <summary>
 /// Visits <see cref="SelectProvider"/>.
 /// </summary>
 /// <param name="provider">Select provider.</param>
 protected abstract Provider VisitSelect(SelectProvider provider);