protected override Expression VisitClientJoin(ClientJoinExpression join)
{
// convert client join into a up-front lookup table builder and 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[] { innerKey.Type, join.Projection.Projector.Type });
Expression constructKVPair = Expression.New(kvpConstructor, innerKey, join.Projection.Projector);
ProjectionExpression newProjection = new ProjectionExpression(join.Projection.Source, constructKVPair);
int iLookup = ++nLookup;
Expression execution = 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.NotEqual(
Expression.PropertyOrField(kvp, "Value"),
Expression.Constant(null, join.Projection.Projector.Type)
),
kvp
);
execution = Expression.Call(typeof(Enumerable), "Where", new[] { 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[] { 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(), Visit(outerKey));
if (join.Projection.Aggregator != null)
{
// apply aggregator
access = DbExpressionReplacer.Replace(join.Projection.Aggregator.Body,
join.Projection.Aggregator.Parameters[0], access);
}
variables.Add(lookup);
initializers.Add(toLookup);
return(access);
}
// end mike
private Expression ExecuteProjection(ProjectionExpression projection, bool okayToDefer)
{
okayToDefer &= (receivingMember != null && policy.IsDeferLoaded(receivingMember));
// parameterize query
projection = (ProjectionExpression)Parameterizer.Parameterize(projection);
if (scope != null)
{
// also convert references to outer alias to named values! these become SQL parameters too
projection = (ProjectionExpression)OuterParameterizer.Parameterize(scope.Alias, projection);
}
var saveScope = scope;
ParameterExpression reader = Expression.Parameter(typeof(DbDataReader), "r" + nReaders++);
scope = new Scope(scope, reader, projection.Source.Alias, projection.Source.Columns);
LambdaExpression projector = Expression.Lambda(Visit(projection.Projector), reader);
scope = saveScope;
List <string> columnNames = ColumnNamedGatherer.Gather(projector.Body); //mike
string commandText = policy.Mapping.Language.Format(projection.Source);
ReadOnlyCollection <NamedValueExpression> namedValues = NamedValueGatherer.Gather(projection.Source);
string[] names = namedValues.Select(v => v.Name).ToArray();
Expression[] values = namedValues.Select(v => Expression.Convert(Visit(v.Value), typeof(object))).ToArray();
string methExecute = okayToDefer
? "ExecuteDeferred"
: "Execute";
if (okayToDefer)
{
}
// call low-level execute directly on supplied DbQueryProvider
Expression result = Expression.Call(provider, methExecute, new[] { projector.Body.Type },
Expression.New(
typeof(QueryCommand <>).MakeGenericType(projector.Body.Type).
GetConstructors()[0],
Expression.Constant(commandText),
Expression.Constant(names),
projector, Expression.Constant(columnNames)
),
Expression.NewArrayInit(typeof(object), values)
);
if (projection.Aggregator != null)
{
// apply aggregator
result = DbExpressionReplacer.Replace(projection.Aggregator.Body, projection.Aggregator.Parameters[0],
result);
}
return(result);
}
