// public static methods
public static AstPipeline Translate(TranslationContext context, MethodCallExpression expression)
{
var method = expression.Method;
var arguments = expression.Arguments;
if (method.Is(QueryableMethod.Select))
{
var sourceExpression = arguments[0];
var pipeline = ExpressionToPipelineTranslator.Translate(context, sourceExpression);
var sourceSerializer = pipeline.OutputSerializer;
var selectorLambda = ExpressionHelper.UnquoteLambda(arguments[1]);
if (selectorLambda.Body == selectorLambda.Parameters[0])
{
return(pipeline); // ignore identity projection: Select(x => x)
}
var selectorTranslation = ExpressionToAggregationExpressionTranslator.TranslateLambdaBody(context, selectorLambda, sourceSerializer, asRoot: true);
var(projectStage, projectionSerializer) = ProjectionHelper.CreateProjectStage(selectorTranslation);
pipeline = pipeline.AddStages(projectionSerializer, projectStage);
return(pipeline);
}
throw new ExpressionNotSupportedException(expression);
}
// public static methods
public static AstPipeline Translate(TranslationContext context, MethodCallExpression expression)
{
var method = expression.Method;
var arguments = expression.Arguments;
if (method.Is(QueryableMethod.Join))
{
var outerExpression = arguments[0];
var pipeline = ExpressionToPipelineTranslator.Translate(context, outerExpression);
var outerSerializer = pipeline.OutputSerializer;
var wrapOuterStage = AstStage.Project(
AstProject.Set("_outer", AstExpression.Var("ROOT")),
AstProject.ExcludeId());
var wrappedOuterSerializer = WrappedValueSerializer.Create("_outer", outerSerializer);
var innerExpression = arguments[1];
var(innerCollectionName, innerSerializer) = innerExpression.GetCollectionInfo(containerExpression: expression);
var outerKeySelectorLambda = ExpressionHelper.UnquoteLambda(arguments[2]);
var localFieldPath = outerKeySelectorLambda.GetFieldPath(context, wrappedOuterSerializer);
var innerKeySelectorLambda = ExpressionHelper.UnquoteLambda(arguments[3]);
var foreignFieldPath = innerKeySelectorLambda.GetFieldPath(context, innerSerializer);
var lookupStage = AstStage.Lookup(
from: innerCollectionName,
match: new AstLookupStageEqualityMatch(localFieldPath, foreignFieldPath),
@as: "_inner");
var unwindStage = AstStage.Unwind("_inner");
var resultSelectorLambda = ExpressionHelper.UnquoteLambda(arguments[4]);
var root = AstExpression.Var("ROOT", isCurrent: true);
var outerParameter = resultSelectorLambda.Parameters[0];
var outerField = AstExpression.GetField(root, "_outer");
var outerSymbol = context.CreateSymbol(outerParameter, outerField, outerSerializer);
var innerParameter = resultSelectorLambda.Parameters[1];
var innerField = AstExpression.GetField(root, "_inner");
var innerSymbol = context.CreateSymbol(innerParameter, innerField, innerSerializer);
var resultSelectorContext = context.WithSymbols(outerSymbol, innerSymbol);
var resultSelectorTranslation = ExpressionToAggregationExpressionTranslator.Translate(resultSelectorContext, resultSelectorLambda.Body);
var(projectStage, newOutputSerializer) = ProjectionHelper.CreateProjectStage(resultSelectorTranslation);
pipeline = pipeline.AddStages(
newOutputSerializer,
wrapOuterStage,
lookupStage,
unwindStage,
projectStage);
return(pipeline);
}
throw new ExpressionNotSupportedException(expression);
}
private static AstPipeline TranslateResultSelector(
TranslationContext context,
AstPipeline pipeline,
ReadOnlyCollection <Expression> arguments,
IBsonSerializer keySerializer,
IBsonSerializer elementSerializer)
{
var resultSelectorLambda = ExpressionHelper.UnquoteLambda(arguments.Last());
var root = AstExpression.Var("ROOT", isCurrent: true);
var keyParameter = resultSelectorLambda.Parameters[0];
var keyField = AstExpression.GetField(root, "_id");
var keySymbol = context.CreateSymbol(keyParameter, keyField, keySerializer);
var elementsParameter = resultSelectorLambda.Parameters[1];
var elementsField = AstExpression.GetField(root, "_elements");
var elementsSerializer = IEnumerableSerializer.Create(elementSerializer);
var elementsSymbol = context.CreateSymbol(elementsParameter, elementsField, elementsSerializer);
var resultSelectContext = context.WithSymbols(keySymbol, elementsSymbol);
var resultSelectorTranslation = ExpressionToAggregationExpressionTranslator.Translate(resultSelectContext, resultSelectorLambda.Body);
var(projectStage, projectionSerializer) = ProjectionHelper.CreateProjectStage(resultSelectorTranslation);
return(pipeline.AddStages(projectionSerializer, projectStage));
}
