private BsonDocument TranslateProjectValue(Expression selector)
{
BsonDocument projectValue;
var result = AggregateLanguageTranslator.Translate(selector, _translationOptions);
if (result.BsonType == BsonType.String)
{
// this means we got back a field expression prefixed with a $ sign.
projectValue = new BsonDocument(result.ToString().Substring(1), 1);
}
else if (result.BsonType == BsonType.Document)
{
projectValue = (BsonDocument)result;
}
else
{
throw new NotSupportedException($"The expression {selector.ToString()} is not supported.");
}
if (!projectValue.Contains("_id"))
{
projectValue.Add("_id", 0);
}
return(projectValue);
}
private void VisitDistinct(DistinctExpression node)
{
Visit(node.Source);
var id = new BsonDocument("_id", AggregateLanguageTranslator.Translate(node.Selector));
_stages.Add(new BsonDocument("$group", id));
}
public static BsonValue Translate <TSource, TResult>(
Expression <Func <TSource, TResult> > expression,
IBsonSerializer <TSource> sourceSerializer,
IBsonSerializerRegistry serializerRegistry,
ExpressionTranslationOptions translationOptions)
{
var bindingContext = new PipelineBindingContext(serializerRegistry);
var boundExpression = BindResult(bindingContext, expression, sourceSerializer);
return(AggregateLanguageTranslator.Translate(boundExpression, translationOptions));
}
public static BsonDocument TranslateProject(Expression expression, ExpressionTranslationOptions translationOptions)
{
var projection = (BsonDocument)AggregateLanguageTranslator.Translate(expression, translationOptions);
if (!projection.Contains("_id"))
{
projection.Add("_id", 0);
}
return(projection);
}
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("$group", group));
}
private void TranslateGroupBy(GroupByExpression node)
{
Translate(node.Source);
var groupValue = new BsonDocument();
var idValue = AggregateLanguageTranslator.Translate(node.KeySelector, _translationOptions);
groupValue.Add("_id", idValue);
foreach (var accumulator in node.Accumulators)
{
var accumulatorValue = AggregateLanguageTranslator.Translate(accumulator, _translationOptions);
groupValue.Add(accumulator.FieldName, accumulatorValue);
}
_stages.Add(new BsonDocument("$group", groupValue));
}
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("$group", group));
}
public static RenderedProjectionDefinition <TResult> Translate <TKey, TDocument, TResult>(Expression <Func <TDocument, TKey> > idProjector, Expression <Func <IGrouping <TKey, TDocument>, TResult> > groupProjector, IBsonSerializer <TDocument> parameterSerializer, IBsonSerializerRegistry serializerRegistry, ExpressionTranslationOptions translationOptions)
{
var bindingContext = new PipelineBindingContext(serializerRegistry);
var keySelector = BindKeySelector(bindingContext, idProjector, parameterSerializer);
var boundGroupExpression = BindGroup(bindingContext, groupProjector, parameterSerializer, keySelector);
var projectionSerializer = bindingContext.GetSerializer(boundGroupExpression.Type, boundGroupExpression);
var projection = AggregateLanguageTranslator.Translate(boundGroupExpression, translationOptions).AsBsonDocument;
// must have an "_id" in a group document
if (!projection.Contains("_id"))
{
var idProjection = AggregateLanguageTranslator.Translate(keySelector, translationOptions);
projection.InsertAt(0, new BsonElement("_id", idProjection));
}
return(new RenderedProjectionDefinition <TResult>(projection, (IBsonSerializer <TResult>)projectionSerializer));
}
private void TranslateJoin(JoinExpression node)
{
Translate(node.Source);
var joined = node.Joined as CollectionExpression;
if (joined == null)
{
throw new NotSupportedException("Only a collection is allowed to be joined.");
}
var localFieldValue = AggregateLanguageTranslator.Translate(node.SourceKeySelector, _translationOptions);
if (localFieldValue.BsonType != BsonType.String)
{
throw new NotSupportedException("Could not translate the local field.");
}
var localField = localFieldValue.ToString().Substring(1); // remove '$'
var foreignFieldValue = AggregateLanguageTranslator.Translate(node.JoinedKeySelector, _translationOptions);
if (foreignFieldValue.BsonType != BsonType.String)
{
throw new NotSupportedException("Could not translate the foreign field.");
}
var foreignField = foreignFieldValue.ToString().Substring(1); // remove '$'
_stages.Add(new BsonDocument("$lookup", new BsonDocument
{
{ "from", ((CollectionExpression)node.Joined).CollectionNamespace.CollectionName },
{ "localField", localField },
{ "foreignField", foreignField },
{ "as", node.JoinedItemName }
}));
_stages.Add(new BsonDocument("$unwind", "$" + node.JoinedItemName));
}