public Expression Bind(ProjectionExpression projection, ProjectionBindingContext context, MethodCallExpression node, IEnumerable <Expression> arguments)
{
var id = BindId(projection, context, arguments.Single());
var iGroupingType = typeof(IGrouping <,>).MakeGenericType(id.Type, projection.Projector.Type);
var group = new CorrelatedGroupByExpression(
Guid.NewGuid(),
typeof(IEnumerable <>).MakeGenericType(iGroupingType),
projection.Source,
id,
Enumerable.Empty <Expression>());
var groupingType = typeof(Grouping <,>).MakeGenericType(id.Type, projection.Projector.Type);
Expression selector = Expression.Convert(
Expression.New(
groupingType.GetConstructors()[0],
id),
iGroupingType);
var projector = BuildProjector(projection, context, id, selector);
context.GroupMap.Add(projector, group.CorrelationId);
return(new ProjectionExpression(group, projector));
}
private void VisitCorrelatedGroupBy(CorrelatedGroupByExpression node)
{
Visit(node.Source);
var group = new BsonDocument();
group.Add("_id", AggregateLanguageTranslator.Translate(node.Id));
foreach (var accumulator in node.Accumulators)
{
var serializationExpression = (SerializationExpression)accumulator;
group.Add(
serializationExpression.SerializationInfo.ElementName,
AggregateLanguageTranslator.Translate(serializationExpression.Expression));
}
_stages.Add(new BsonDocument("$group", group));
}
protected internal override Expression VisitCorrelatedGroupBy(CorrelatedGroupByExpression node)
{
if (_lookup != null && _lookup.Contains(node.CorrelationId))
{
var source = Visit(node.Source);
var accumulators = new List <SerializationExpression>();
var comparer = new ExpressionComparer();
foreach (var correlatedAccumulator in _lookup[node.CorrelationId])
{
var index = accumulators.FindIndex(x => comparer.Compare(x.Expression, correlatedAccumulator.Accumulator));
if (index == -1)
{
var serializer = _serializerRegistry.GetSerializer(correlatedAccumulator.Type);
var info = new BsonSerializationInfo(
"__agg" + accumulators.Count,
serializer,
serializer.ValueType);
var serializationExpression = new SerializationExpression(correlatedAccumulator.Accumulator, info);
accumulators.Add(serializationExpression);
_map[correlatedAccumulator] = serializationExpression;
}
else
{
_map[correlatedAccumulator] = accumulators[index];
}
}
node = node.Update(
source,
node.Id,
accumulators.OfType <Expression>());
}
return(base.VisitCorrelatedGroupBy(node));
}