public override Expression?Visit(Expression?expression)
{
if (this.candidates.Contains(expression !))
{
if (expression is ColumnExpression column)
{
if (!projectTrivialColumns)
{
return(expression);
}
if (this.map.TryGetValue(column, out var mapped))
{
return(mapped);
}
mapped = generator.MapColumn(column).GetReference(newAlias);
this.map[column] = mapped;
return(mapped);
}
else
{
if (expression !.Type.UnNullify().IsEnum)
{
var convert = expression.TryConvert(expression.Type.IsNullable() ? typeof(int?) : typeof(int));
return(generator.NewColumn(convert).GetReference(newAlias).TryConvert(expression.Type));
}
protected internal override Expression VisitProjection(ProjectionExpression proj)
{
if (currentSource == null)
{
currentSource = WithoutOrder(proj.Select);
Expression projector = this.Visit(proj.Projector);
if (projector != proj.Projector)
{
proj = new ProjectionExpression(proj.Select, projector, proj.UniqueFunction, proj.Type);
}
currentSource = null;
return(proj);
}
else
{
HashSet <ColumnExpression> columns = ExternalColumnGatherer.Gatherer(proj, currentSource.Alias);
if (columns.Count == 0)
{
Expression projector = Visit(proj.Projector);
ConstantExpression key = Expression.Constant(0);
Type kvpType = typeof(KeyValuePair <,>).MakeGenericType(key.Type, projector.Type);
ConstructorInfo ciKVP = kvpType.GetConstructor(new[] { key.Type, projector.Type }) !;
Type projType = proj.UniqueFunction == null ? typeof(IEnumerable <>).MakeGenericType(kvpType) : kvpType;
var childProj = new ProjectionExpression(proj.Select,
Expression.New(ciKVP, key, projector), proj.UniqueFunction, projType);
return(new ChildProjectionExpression(childProj,
Expression.Constant(0), inMList != null, inMList ?? proj.Type, new LookupToken()));
}
else
{
SelectExpression external;
IEnumerable <ColumnExpression> externalColumns;
if (!IsKey(currentSource, columns))
{
Alias aliasDistinct = aliasGenerator.GetUniqueAlias(currentSource.Alias.Name + "D");
ColumnGenerator generatorDistinct = new ColumnGenerator();
List <ColumnDeclaration> columnDistinct = columns.Select(ce => generatorDistinct.MapColumn(ce)).ToList();
external = new SelectExpression(aliasDistinct, true, null, columnDistinct, currentSource, null, null, null, 0);
Dictionary <ColumnExpression, ColumnExpression> distinctReplacements = columnDistinct.ToDictionary(
cd => (ColumnExpression)cd.Expression,
cd => cd.GetReference(aliasDistinct));
proj = (ProjectionExpression)ColumnReplacer.Replace(proj, distinctReplacements);
externalColumns = distinctReplacements.Values.ToHashSet();
}
else
{
external = currentSource;
externalColumns = columns;
}
ColumnGenerator generatorSM = new ColumnGenerator();
List <ColumnDeclaration> columnsSMExternal = externalColumns.Select(ce => generatorSM.MapColumn(ce)).ToList();
List <ColumnDeclaration> columnsSMInternal = proj.Select.Columns.Select(cd => generatorSM.MapColumn(cd.GetReference(proj.Select.Alias))).ToList();
SelectExpression @internal = ExtractOrders(proj.Select, out List <OrderExpression>?innerOrders);
Alias aliasSM = aliasGenerator.GetUniqueAlias(@internal.Alias.Name + "SM");
SelectExpression selectMany = new SelectExpression(aliasSM, false, null, columnsSMExternal.Concat(columnsSMInternal),
new JoinExpression(JoinType.CrossApply,
external,
@internal, null), null, innerOrders, null, 0);
SelectExpression old = currentSource;
currentSource = WithoutOrder(selectMany);
var selectManyReplacements = selectMany.Columns.ToDictionary(
cd => (ColumnExpression)cd.Expression,
cd => cd.GetReference(aliasSM));
Expression projector = ColumnReplacer.Replace(proj.Projector, selectManyReplacements);
projector = Visit(projector);
currentSource = old;
Expression key = TupleReflection.TupleChainConstructor(columnsSMExternal.Select(cd => MakeEquatable(cd.GetReference(aliasSM))));
Type kvpType = typeof(KeyValuePair <,>).MakeGenericType(key.Type, projector.Type);
ConstructorInfo ciKVP = kvpType.GetConstructor(new[] { key.Type, projector.Type }) !;
Type projType = proj.UniqueFunction == null ? typeof(IEnumerable <>).MakeGenericType(kvpType) : kvpType;
var childProj = new ProjectionExpression(selectMany,
Expression.New(ciKVP, key, projector), proj.UniqueFunction, projType);
return(new ChildProjectionExpression(childProj,
TupleReflection.TupleChainConstructor(columns.Select(a => MakeEquatable(a))), inMList != null, inMList ?? proj.Type, new LookupToken()));
}
}
}
