object IODataSerializer.Serialize <TElement>(IODataProjectResult <TElement> projectResult)
{
Throw.IfNull(projectResult, "projectResult");
// TODO VNext this doesn't seem like the best place for this logic. Consider changing
// the pipeline APIs so that this logic can happen earlier
IEnumerable projectedQuery;
int? inlineCount;
PaginationHelper.Paginate(projectResult, out projectedQuery, out inlineCount);
var result = this.Serialize(projectedQuery, projectResult.ProjectMapping, inlineCount);
return(result);
}
object IODataServiceQueryPipeline.Serialize <TElement>(IODataProjectResult <TElement> projectResult)
{
Throw.IfNull(projectResult, "projectResult");
// MA: TryGetValue throws on nulls, so we need this to be a separate check
Throw <NotSupportedException> .If(projectResult.ODataQuery.Format == null, "No format argument was provided");
Throw <NotSupportedException> .If(
!this._serializersByFormat.TryGetValue(projectResult.ODataQuery.Format, out var serializer),
"No serializer is available for the given format"
);
var result = serializer.Serialize(projectResult);
return(result);
}
/// <summary>
/// Optimizes pagination and counting by avoiding projection reads when <see cref="ODataQueryExpression.Top"/> is 0 and
/// avoiding counts when on the last page of items (where count can be inferred)
/// </summary>
public static void Paginate <TElement>(IODataProjectResult <TElement> projectResult, out IEnumerable projectEnumerable, out int?count)
{
// if we're doing top(0), we can skip projection and just count. This is the case when a client calls .Count() on an OData queryable
if (projectResult.ODataQuery.Top == 0)
{
projectEnumerable = Enumerable.Empty <object>();
count = projectResult.ODataQuery.InlineCount == ODataInlineCountOption.AllPages
? projectResult.InlineCountQuery.Count()
: default(int?);
return;
}
// if we're counting...
if (projectResult.ODataQuery.InlineCount == ODataInlineCountOption.AllPages)
{
// Enumerable.Cast to ensure in-memory cast
var projectArray = Enumerable.Cast <object>(projectResult.ProjectedResultQuery).ToArray();
projectEnumerable = projectArray;
// ... and we're on the last page, we can skip the count
if (!projectResult.ODataQuery.Top.HasValue ||
projectArray.Length < projectResult.ODataQuery.Top.Value)
{
count = projectResult.ODataQuery.Skip + projectArray.Length;
}
else
{
count = projectResult.InlineCountQuery.Count();
}
return;
}
// otherwise, don't count
projectEnumerable = projectResult.ProjectedResultQuery;
count = null;
}
