public static IFastCollectionEnumerable <TResult> Select <TSource, TResult>(
[NotNull] this IFastCollectionEnumerable <TSource> source,
[NotNull] Expression <Func <TSource, TResult> > selector)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
if (selector == null)
{
throw new ArgumentNullException(nameof(selector));
}
var sourceIterator = source.ExtractIterator();
// In linq pipeline:
// 1) Select clause changes operation target
var newOperationTarget = sourceIterator.OperationTarget.ExtendWithSelector(selector);
// 2) Select clause changes data
var compiledSelector = selector.Compile();
var newItemsEnumerable = sourceIterator.ItemsEnumerable.Select(x => new FastCollectionItem <TResult>(x.Id, compiledSelector(x.Data)));
var fastCollectionSelectEnumerable = new FastCollectionIterator <TResult>(sourceIterator.SourceCollection, newOperationTarget, newItemsEnumerable);
return(fastCollectionSelectEnumerable);
}
public static IFastCollectionEnumerable <TSource> Where <TSource>(
[NotNull] this IFastCollectionEnumerable <TSource> source,
[NotNull] Expression <Func <TSource, bool> > predicate)
{
if (source == null)
{
throw new ArgumentNullException(nameof(source));
}
if (predicate == null)
{
throw new ArgumentNullException(nameof(predicate));
}
var sourceIterator = source.ExtractIterator();
var filter = new FiltersParser().ParsePredicate(predicate, sourceIterator.OperationTarget);
var filtersExecutor = new FiltersExecutor();
var preparedFilterExecution = filtersExecutor.PrepareExecution(filter, sourceIterator.SourceCollection.IndicesCoverage);
if (preparedFilterExecution.CanBeExecuted)
{
// We can use indices for execution
return(new FastCollectionLazyIterator <TSource>(
sourceIterator.SourceCollection,
sourceIterator.OperationTarget,
() =>
{
// This lambda will be called on items demand
var cuttedIds = new HashSet <int>(preparedFilterExecution.ExecuteAction());
return sourceIterator.ItemsEnumerable.Where(x => cuttedIds.Contains(x.Id));
}));
}
else
{
// In this case we can't use indices for execution and we have to check each item
var compiledPredicate = predicate.Compile();
var newItemsEnumerable = sourceIterator.ItemsEnumerable.Where(x => compiledPredicate(x.Data));
var fastCollectionWhereEnumerable = new FastCollectionIterator <TSource>(sourceIterator.SourceCollection, sourceIterator.OperationTarget, newItemsEnumerable);
return(fastCollectionWhereEnumerable);
}
}