protected virtual Expression VisitProjection(ProjectionExpression projection)
{
var source = (SelectExpression)Visit(projection.Source);
var projector = Visit(projection.Projector);
if (source != projection.Source || projector != projection.Projector)
return new ProjectionExpression(source, projector, projection.Aggregator);
return projection;
}
protected override Expression VisitProjection(ProjectionExpression projection)
{
var queryObject = new MongoQueryObjectBuilder().Build(projection);
queryObject.Projector = new ProjectionBuilder().Build(projection.Projector, queryObject.DocumentType, "document", queryObject.IsMapReduce);
queryObject.Aggregator = (LambdaExpression)Visit(projection.Aggregator);
Expression result = Expression.Call(
_provider,
"ExecuteQueryObject",
Type.EmptyTypes,
Expression.Constant(queryObject, typeof(MongoQueryObject)));
if (queryObject.Aggregator != null)
result = Expression.Convert(result, queryObject.Aggregator.Body.Type);
else
result = Expression.Convert(result, typeof(IEnumerable<>).MakeGenericType(queryObject.Projector.Body.Type));
return result;
}
protected virtual Expression BindGroupBy(Expression source, LambdaExpression keySelector, LambdaExpression elementSelector, LambdaExpression resultSelector)
{
var projection = VisitSequence(source);
_map[keySelector.Parameters[0]] = projection.Projector;
var keyExpression = Visit(keySelector.Body);
var elementExpression = projection.Projector;
if (elementSelector != null)
{
_map[elementSelector.Parameters[0]] = projection.Projector;
elementExpression = Visit(elementSelector.Body);
}
var subqueryBasis = VisitSequence(source);
_map[keySelector.Parameters[0]] = subqueryBasis.Projector;
var subqueryKeyExpression = Visit(keySelector.Body);
var subqueryCorrelation = Expression.Equal(keyExpression, subqueryKeyExpression);
var subqueryElementExpression = subqueryBasis.Projector;
if (elementSelector != null)
{
_map[elementSelector.Parameters[0]] = subqueryBasis.Projector;
subqueryElementExpression = Visit(elementSelector.Body);
}
var elementAlias = new Alias();
var elementProjection = _projector.ProjectFields(subqueryElementExpression, elementAlias, subqueryBasis.Source.Alias);
var elementSubquery =
new ProjectionExpression(
new SelectExpression(elementAlias, elementProjection.Fields, subqueryBasis.Source, subqueryCorrelation),
elementProjection.Projector);
var alias = new Alias();
var info = new GroupByInfo(alias, elementExpression);
_groupByMap[elementSubquery] = info;
Expression resultExpression;
if (resultSelector != null)
{
var saveGroupElement = _currentGroupElement;
_currentGroupElement = elementSubquery;
_map[resultSelector.Parameters[0]] = keyExpression;
_map[resultSelector.Parameters[1]] = elementSubquery;
resultExpression = Visit(resultSelector.Body);
_currentGroupElement = saveGroupElement;
}
else
{
resultExpression = Expression.New(
typeof(Grouping<,>).MakeGenericType(keyExpression.Type, subqueryElementExpression.Type).GetConstructors()[0],
new[] { keyExpression, elementSubquery });
}
var fieldProjection = _projector.ProjectFields(resultExpression, alias, projection.Source.Alias);
var projectedElementSubquery = ((NewExpression)fieldProjection.Projector).Arguments[1];
_groupByMap[projectedElementSubquery] = info;
return new ProjectionExpression(
new SelectExpression(alias, new FieldDeclaration[0], projection.Source, null, null, keyExpression, false, null, null),
fieldProjection.Projector);
}
private Expression BindFirstOrSingle(Expression source, LambdaExpression predicate, string kind, bool isRoot)
{
var projection = VisitSequence(source);
Expression where = null;
if (predicate != null)
{
_map[predicate.Parameters[0]] = projection.Projector;
where = Visit(predicate.Body);
}
Expression take = kind.StartsWith("First") ? Expression.Constant(1) : null;
if (take == null & kind.StartsWith("Single"))
take = Expression.Constant(2);
if (take != null || where != null)
{
var alias = new Alias();
var fieldProjection = _projector.ProjectFields(projection.Projector, alias, projection.Source.Alias);
projection = new ProjectionExpression(
new SelectExpression(alias, fieldProjection.Fields, projection.Source, where, null, null, false, null, take),
fieldProjection.Projector);
}
if (isRoot)
{
var elementType = projection.Projector.Type;
var p = Expression.Parameter(typeof(IEnumerable<>).MakeGenericType(elementType), "p");
var lambda = Expression.Lambda(Expression.Call(typeof(Enumerable), kind, new[] { elementType }, p), p);
return new ProjectionExpression(projection.Source, projection.Projector, lambda);
}
return projection;
}
protected virtual bool CompareProjection(ProjectionExpression a, ProjectionExpression b)
{
if (!Compare(a.Source, b.Source))
return false;
var save = _aliasScope;
try
{
_aliasScope = new ScopedDictionary<Alias, Alias>(_aliasScope);
_aliasScope.Add(a.Source.Alias, b.Source.Alias);
return Compare(a.Projector, b.Projector)
&& Compare(a.Aggregator, b.Aggregator)
&& a.IsSingleton == b.IsSingleton;
}
finally
{
_aliasScope = save;
}
}