private static IEnumerable <CosmosElement> ProjectOnGroupings(
IEnumerable <IGrouping <GroupByKey, CosmosElement> > groupings,
SqlSelectClause sqlSelectClause)
{
foreach (IGrouping <GroupByKey, CosmosElement> grouping in groupings)
{
IEnumerable <CosmosElement> dataSource = grouping;
if (AggregateProjectionDector.HasAggregate(sqlSelectClause.SelectSpec))
{
// If there is an aggregate then we need to just project out the one document
// But we need to transform the query to first evaluate the aggregate on all the documents
AggregateProjectionTransformer aggregateProjectionTransformer = new AggregateProjectionTransformer(dataSource);
SqlSelectSpec transformedSpec = aggregateProjectionTransformer
.TransformAggregatesInProjection(sqlSelectClause.SelectSpec);
CosmosElement aggregationResult = transformedSpec.Accept(
Projector.Singleton,
dataSource.FirstOrDefault());
if (aggregationResult != null)
{
dataSource = new CosmosElement[] { aggregationResult };
}
else
{
dataSource = Array.Empty <CosmosElement>();
}
}
else
{
dataSource = dataSource
.Select(element => sqlSelectClause.SelectSpec.Accept(
Projector.Singleton,
element))
.Where(projection => projection != Undefined);
}
if (dataSource.Any())
{
yield return(dataSource.First());
}
}
}
/// <summary>
/// Determines whether or not the SqlSelectSpec has an aggregate in the outer most query.
/// </summary>
/// <param name="selectSpec">The select spec to traverse.</param>
/// <returns>Whether or not the SqlSelectSpec has an aggregate in the outer most query.</returns>
public static bool HasAggregate(SqlSelectSpec selectSpec)
{
return(selectSpec.Accept(AggregateProjectionDectorVisitor.Singleton));
}
private static void AssertEvaluation(CosmosElement expected, SqlSelectSpec sqlSelectSpec, CosmosElement document = null)
{
CosmosElement evaluation = sqlSelectSpec.Accept(Projector.Singleton, document);
Assert.AreEqual(expected, evaluation);
}
public SqlSelectSpec TransformAggregatesInProjection(SqlSelectSpec selectSpec)
{
return(selectSpec.Accept(this.visitor));
}