protected virtual Expression VisitOuterJoined(DbOuterJoinedExpression outer)
{
var test = this.Visit(outer.Test);
var expression = this.Visit(outer.Expression);
return(this.UpdateOuterJoined(outer, test, expression));
}
protected DbOuterJoinedExpression UpdateOuterJoined(DbOuterJoinedExpression outer, Expression test, Expression expression)
{
if (test != outer.Test || expression != outer.Expression)
{
return(new DbOuterJoinedExpression(test, expression));
}
return(outer);
}
protected virtual Expression VisitOuterJoined(DbOuterJoinedExpression outer)
{
this.Write("Outer(");
this.WriteLine(Indentation.Inner);
this.Visit(outer.Test);
this.Write(", ");
this.WriteLine(Indentation.Same);
this.Visit(outer.Expression);
this.WriteLine(Indentation.Outer);
this.Write(")");
return(outer);
}
public static DbProjectionExpression AddOuterJoinTest(this DbProjectionExpression proj, QueryLanguage language, Expression expression)
{
var colName = proj.Select.Columns.GetAvailableColumnName("Test");
var colType = language.TypeSystem.GetColumnType(expression.Type);
var newSource = proj.Select.AddColumn(new DbColumnDeclaration(colName, expression, colType));
var newProjector = new DbOuterJoinedExpression
(
new DbColumnExpression(expression.Type, colType, newSource.Alias, colName),
proj.Projector
);
return(new DbProjectionExpression(newSource, newProjector, proj.Aggregator));
}
protected override Expression VisitOuterJoined(DbOuterJoinedExpression outer)
{
var expr = this.Visit(outer.Expression);
var column = outer.Test as DbColumnExpression;
if (this.scope.TryGetValue(column, out ParameterExpression reader, out int iOrdinal))
{
return(Expression.Condition
(
Expression.Call(reader, "IsDbNull", null, Expression.Constant(iOrdinal)),
Expression.Constant(TypeHelper.GetDefault(outer.Type), outer.Type),
expr
));
}
return(expr);
}
