public AggregateSubqueryExpression(Alias groupByAlias, Expression aggregateInGroupSelect, ScalarExpression aggregateAsSubquery)
: base(MongoExpressionType.AggregateSubquery, aggregateAsSubquery.Type)
{
GroupByAlias = groupByAlias;
AggregateInGroupSelect = aggregateInGroupSelect;
AggregateAsSubquery = aggregateAsSubquery;
}
public AggregateSubqueryExpression(Alias groupByAlias, Expression aggregateInGroupSelect, ScalarExpression aggregateAsSubquery)
: base(MongoExpressionType.AggregateSubquery, aggregateAsSubquery.Type)
{
GroupByAlias = groupByAlias;
AggregateInGroupSelect = aggregateInGroupSelect;
AggregateAsSubquery = aggregateAsSubquery;
}
protected virtual Expression VisitScalar(ScalarExpression scalar)
{
SelectExpression select = (SelectExpression)Visit(scalar.Select);
if (select != scalar.Select)
{
return(new ScalarExpression(scalar.Type, select));
}
return(scalar);
}
protected virtual Expression VisitAggregateSubquery(AggregateSubqueryExpression aggregateSubquery)
{
Expression e = Visit(aggregateSubquery.AggregateAsSubquery);
ScalarExpression subquery = (ScalarExpression)e;
if (subquery != aggregateSubquery.AggregateAsSubquery)
{
return(new AggregateSubqueryExpression(aggregateSubquery.GroupByAlias, aggregateSubquery.AggregateInGroupSelect, subquery));
}
return(aggregateSubquery);
}
protected override Expression VisitScalar(ScalarExpression scalar)
{
return scalar;
}
private Expression BindAggregate(Expression source, MethodInfo method, LambdaExpression argument, bool isRoot)
{
var returnType = method.ReturnType;
var aggregateType = GetAggregateType(method.Name);
bool hasPredicateArgument = HasPredicateArgument(aggregateType);
bool distinct = false;
bool argumentWasPredicate = false;
var methodCallExpression = source as MethodCallExpression;
if (methodCallExpression != null && !hasPredicateArgument && argument == null)
{
if (methodCallExpression.Method.Name == "Distinct" && methodCallExpression.Arguments.Count == 1
&& (methodCallExpression.Method.DeclaringType == typeof(Queryable) || methodCallExpression.Method.DeclaringType == typeof(Enumerable)))
{
source = methodCallExpression.Arguments[0];
distinct = true;
}
}
if (argument != null && hasPredicateArgument)
{
source = Expression.Call(typeof(Queryable), "Where", method.GetGenericArguments(), source, argument);
argument = null;
argumentWasPredicate = true;
}
var projection = VisitSequence(source);
Expression argExpression = null;
if (argument != null)
{
_map[argument.Parameters[0]] = projection.Projector;
argExpression = Visit(argument.Body);
}
else if (!hasPredicateArgument)
argExpression = projection.Projector;
var alias = new Alias();
Expression aggregateExpression = new AggregateExpression(returnType, aggregateType, argExpression, distinct);
var selectType = typeof(IEnumerable<>).MakeGenericType(returnType);
string fieldName = "_$agg" + (_aggregateCount++);
var select = new SelectExpression(alias, new[] { new FieldDeclaration(fieldName, aggregateExpression) }, projection.Source, null);
if (isRoot)
{
var parameter = Expression.Parameter(selectType, "p");
var lambda = Expression.Lambda(Expression.Call(typeof(Enumerable), "Single", new[] { returnType }, parameter), parameter);
return new ProjectionExpression(
select,
new FieldExpression(aggregateExpression, alias, fieldName),
lambda);
}
var subquery = new ScalarExpression(returnType, select);
GroupByInfo info;
if (!argumentWasPredicate && _groupByMap.TryGetValue(projection, out info))
{
if (argument != null)
{
_map[argument.Parameters[0]] = info.Element;
argExpression = Visit(argument.Body);
}
else if (!hasPredicateArgument)
argExpression = info.Element;
aggregateExpression = new AggregateExpression(returnType, aggregateType, argExpression, distinct);
if (projection == _currentGroupElement)
return aggregateExpression;
return new AggregateSubqueryExpression(info.Alias, aggregateExpression, subquery);
}
return subquery;
}
protected virtual bool CompareScalar(ScalarExpression a, ScalarExpression b)
{
return(Compare(a.Select, b.Select));
}
protected virtual Expression VisitScalar(ScalarExpression scalar)
{
SelectExpression select = (SelectExpression)Visit(scalar.Select);
if (select != scalar.Select)
return new ScalarExpression(scalar.Type, select);
return scalar;
}
protected virtual bool CompareScalar(ScalarExpression a, ScalarExpression b)
{
return Compare(a.Select, b.Select);
}