/// <inheritdoc/>
protected override SqlProvider VisitDistinct(DistinctProvider provider)
{
var source = Compile(provider.Source);
var sourceSelect = source.Request.Statement;
SqlSelect query;
if (!sourceSelect.Limit.IsNullReference() || !sourceSelect.Offset.IsNullReference())
{
var queryRef = SqlDml.QueryRef(sourceSelect);
query = SqlDml.Select(queryRef);
query.Columns.AddRange(queryRef.Columns.Cast <SqlColumn>());
}
else
{
query = sourceSelect.ShallowClone();
}
query.Distinct = true;
return(CreateProvider(query, provider, source));
}
/// <summary> /// Compiles <see cref="DistinctProvider"/>. /// </summary> /// <param name="provider">Distinct provider.</param> protected abstract TResult VisitDistinct(DistinctProvider provider);
