public override Expression Bind(ProjectionExpression projection, ProjectionBindingContext context, MethodCallExpression node, IEnumerable<Expression> arguments)
{
LambdaExpression aggregator;
if (node.Method.Name.EndsWith("Async"))
{
aggregator = CreateAsyncAggregator();
}
else
{
aggregator = CreateSyncAggregator();
}
var source = projection.Source;
var argument = arguments.FirstOrDefault();
if (argument != null && ExtensionExpressionVisitor.IsLambda(argument))
{
source = BindPredicate(projection, context, source, argument);
}
source = new TakeExpression(source, 1);
var serializer = context.SerializerRegistry.GetSerializer(typeof(int));
var accumulator = new AccumulatorExpression(typeof(int), AccumulatorType.Count, null);
var serializationAccumulator = new SerializationExpression(
accumulator,
new BsonSerializationInfo("__agg0", serializer, serializer.ValueType));
var rootAccumulator = new RootAccumulatorExpression(source, serializationAccumulator);
return new ProjectionExpression(
rootAccumulator,
serializationAccumulator,
aggregator);
}
public override Expression Bind(Expressions.ProjectionExpression projection, ProjectionBindingContext context, System.Linq.Expressions.MethodCallExpression node, IEnumerable<System.Linq.Expressions.Expression> arguments)
{
var aggregatorName = "Single";
var returnType = node.Method.ReturnType;
if (node.Method.Name.EndsWith("Async"))
{
aggregatorName += "Async";
returnType = returnType.GetGenericArguments()[0];
}
var aggregator = CreateAggregator(aggregatorName, returnType);
var source = projection.Source;
var argument = arguments.FirstOrDefault();
if (argument != null && ExtensionExpressionVisitor.IsLambda(argument))
{
var lambda = ExtensionExpressionVisitor.GetLambda(argument);
var binder = new AccumulatorBinder(context.GroupMap, context.SerializerRegistry);
binder.RegisterParameterReplacement(lambda.Parameters[0], projection.Projector);
argument = binder.Bind(lambda.Body);
}
else
{
argument = projection.Projector;
var select = source as SelectExpression;
if (select != null)
{
source = select.Source;
}
}
var serializer = context.SerializerRegistry.GetSerializer(returnType);
var accumulator = new AccumulatorExpression(returnType, AccumulatorType, argument);
var serializationAccumulator = new SerializationExpression(
accumulator,
new BsonSerializationInfo("__agg0", serializer, serializer.ValueType));
var rootAccumulator = new RootAccumulatorExpression(source, serializationAccumulator);
return new ProjectionExpression(
rootAccumulator,
serializationAccumulator,
aggregator);
}
protected internal virtual Expression VisitRootAccumulator(RootAccumulatorExpression node)
{
return(node.Update(
Visit(node.Source),
Visit(node.Accumulator)));
}
private void VisitRootAccumulator(RootAccumulatorExpression node)
{
Visit(node.Source);
var group = new BsonDocument("_id", BsonNull.Value);
var serializationAccumulator = (SerializationExpression)node.Accumulator;
group.Add(
serializationAccumulator.SerializationInfo.ElementName,
AggregateLanguageTranslator.Translate(serializationAccumulator.Expression));
_stages.Add(new BsonDocument("$group", group));
}
protected internal virtual Expression VisitRootAccumulator(RootAccumulatorExpression node)
{
return node.Update(
Visit(node.Source),
Visit(node.Accumulator));
}
