protected internal virtual Expression VisitGroupBy(GroupByExpression node)
{
return node.Update(
Visit(node.Source),
Visit(node.KeySelector),
VisitAndConvert(node.Accumulators, "VisitGroupBy"));
}
private void TranslateGroupBy(GroupByExpression node)
{
Translate(node.Source);
var groupValue = new BsonDocument();
var idValue = AggregateLanguageTranslator.Translate(node.KeySelector);
groupValue.Add("_id", idValue);
foreach (var accumulator in node.Accumulators)
{
var accumulatorValue = AggregateLanguageTranslator.Translate(accumulator);
groupValue.Add(accumulator.FieldName, accumulatorValue);
}
_stages.Add(new BsonDocument("$group", groupValue));
}
private Expression VisitCorrelatedGroup(CorrelatedExpression node)
{
var groupExpression = (GroupByExpression)node.Expression;
if (_accumulatorLookup != null && _accumulatorLookup.Contains(node.CorrelationId))
{
var source = Visit(groupExpression.Source);
var accumulators = new List<AccumulatorExpression>();
var fieldExpressions = new List<FieldExpression>();
var comparer = new ExpressionComparer();
foreach (var correlatedAccumulator in _accumulatorLookup[node.CorrelationId])
{
var index = accumulators.FindIndex(x => comparer.Compare((Expression)x, correlatedAccumulator.Expression));
FieldExpression fieldExpression;
if (index == -1)
{
var accumulator = (AccumulatorExpression)correlatedAccumulator.Expression;
// TODO: might not need to do any renames...
accumulator = new AccumulatorExpression(
accumulator.Type,
"__agg" + accumulators.Count,
accumulator.Serializer,
accumulator.AccumulatorType,
accumulator.Argument);
accumulators.Add(accumulator);
fieldExpression = new FieldExpression(accumulator.FieldName, accumulator.Serializer);
fieldExpressions.Add(fieldExpression);
}
else
{
fieldExpression = fieldExpressions[index];
}
_accumulatorReplacementMap[correlatedAccumulator] = fieldExpression;
}
groupExpression = new GroupByExpression(
groupExpression.Type,
source,
groupExpression.KeySelector,
accumulators.AsReadOnly());
}
return Visit(groupExpression);
}
