protected override Expression VisitClientJoin(ClientJoinExpression join) { var innerKey = this.VisitExpressionList(join.InnerKey); var outerKey = this.VisitExpressionList(join.OuterKey); ProjectionExpression projection = (ProjectionExpression)this.Visit(join.Projection); if (projection != join.Projection || innerKey != join.InnerKey || outerKey != join.OuterKey) { return(new ClientJoinExpression(projection, outerKey, innerKey)); } return(join); }
protected override Expression VisitClientJoin(ClientJoinExpression join) { // treat client joins as new top level var saveTop = this.isTopLevel; var saveSelect = this.currentSelect; this.isTopLevel = true; this.currentSelect = null; Expression result = base.VisitClientJoin(join); this.isTopLevel = saveTop; this.currentSelect = saveSelect; return(result); }
protected override Expression VisitClientJoin(ClientJoinExpression join) { // convert client join into a up-front lookup table builder & replace client-join in tree with lookup accessor // 1) lookup = query.Select(e => new KVP(key: inner, value: e)).ToLookup(kvp => kvp.Key, kvp => kvp.Value) Expression innerKey = MakeJoinKey(join.InnerKey); Expression outerKey = MakeJoinKey(join.OuterKey); ConstructorInfo kvpConstructor = typeof(KeyValuePair <,>).MakeGenericType(innerKey.Type, join.Projection.Projector.Type).GetConstructor(new Type[] { innerKey.Type, join.Projection.Projector.Type }); Expression constructKVPair = Expression.New(kvpConstructor, innerKey, join.Projection.Projector); ProjectionExpression newProjection = new ProjectionExpression(join.Projection.Select, constructKVPair); int iLookup = ++nLookup; Expression execution = this.ExecuteProjection(newProjection, false); ParameterExpression kvp = Expression.Parameter(constructKVPair.Type, "kvp"); // filter out nulls if (join.Projection.Projector.NodeType == (ExpressionType)DbExpressionType.OuterJoined) { LambdaExpression pred = Expression.Lambda( Expression.PropertyOrField(kvp, "Value").NotEqual(TypeHelper.GetNullConstant(join.Projection.Projector.Type)), kvp ); execution = Expression.Call(typeof(Enumerable), "Where", new Type[] { kvp.Type }, execution, pred); } // make lookup LambdaExpression keySelector = Expression.Lambda(Expression.PropertyOrField(kvp, "Key"), kvp); LambdaExpression elementSelector = Expression.Lambda(Expression.PropertyOrField(kvp, "Value"), kvp); Expression toLookup = Expression.Call(typeof(Enumerable), "ToLookup", new Type[] { kvp.Type, outerKey.Type, join.Projection.Projector.Type }, execution, keySelector, elementSelector); // 2) agg(lookup[outer]) ParameterExpression lookup = Expression.Parameter(toLookup.Type, "lookup" + iLookup); PropertyInfo property = lookup.Type.GetProperty("Item"); Expression access = Expression.Call(lookup, property.GetGetMethod(), this.Visit(outerKey)); if (join.Projection.Aggregator != null) { // apply aggregator access = DbExpressionReplacer.Replace(join.Projection.Aggregator.Body, join.Projection.Aggregator.Parameters[0], access); } this.variables.Add(lookup); this.initializers.Add(toLookup); return(access); }