//---------------------------------------------------------------------------------------
// Returns a QueryOperator<T> for any IEnumerable<T> data source. This will just do a
// cast and return a reference to the same data source if the source is another query
// operator, but will lazily allocate a scan operation and return that otherwise.
//
// Arguments:
// source - any enumerable data source to be wrapped
//
// Return Value:
// A query operator.
//
internal static QueryOperator <TOutput> AsQueryOperator(IEnumerable <TOutput> source)
{
Contract.Assert(source != null);
// Just try casting the data source to a query operator, in the case that
// our child is just another query operator.
QueryOperator <TOutput> sourceAsOperator = source as QueryOperator <TOutput>;
if (sourceAsOperator == null)
{
OrderedParallelQuery <TOutput> orderedQuery = source as OrderedParallelQuery <TOutput>;
if (orderedQuery != null)
{
// We have to handle OrderedParallelQuery<T> specially. In all other cases,
// ParallelQuery *is* the QueryOperator<T>. But, OrderedParallelQuery<T>
// is not QueryOperator<T>, it only has a reference to one. Ideally, we
// would want SortQueryOperator<T> to inherit from OrderedParallelQuery<T>,
// but that conflicts with other constraints on our class hierarchy.
sourceAsOperator = (QueryOperator <TOutput>)orderedQuery.SortOperator;
}
else
{
// If the cast failed, then the data source is a real piece of data. We
// just construct a new scan operator on top of it.
sourceAsOperator = new ScanQueryOperator <TOutput>(source);
}
}
Contract.Assert(sourceAsOperator != null);
return(sourceAsOperator);
}
internal override IEnumerator <TSource> GetEnumerator(ParallelMergeOptions?mergeOptions, bool suppressOrderPreservation)
{
ScanQueryOperator <TSource> childAsScan = m_child as ScanQueryOperator <TSource>;
if (childAsScan != null)
{
return(childAsScan.Data.GetEnumerator());
}
return(base.GetEnumerator(mergeOptions, suppressOrderPreservation));
}