public virtual ProjectionExpression AddOuterJoinTest(ProjectionExpression proj)
{
Expression test = GetOuterJoinTest(proj.Select);
SelectExpression select = proj.Select;
ColumnExpression testCol = null;
// look to see if test expression exists in columns already
foreach (ColumnDeclaration col in select.Columns)
{
if (test.Equals(col.Expression))
{
QueryType colType = TypeSystem.GetColumnType(test.Type);
testCol = new ColumnExpression(test.Type, colType, select.Alias, col.Name);
break;
}
}
if (testCol == null)
{
// add expression to projection
testCol = test as ColumnExpression;
string colName = (testCol != null) ? testCol.Name : "Test";
colName = proj.Select.Columns.GetAvailableColumnName(colName);
QueryType colType = TypeSystem.GetColumnType(test.Type);
select = select.AddColumn(new ColumnDeclaration(colName, test, colType));
testCol = new ColumnExpression(test.Type, colType, select.Alias, colName);
}
var newProjector = new OuterJoinedExpression(testCol, proj.Projector);
return(new ProjectionExpression(select, newProjector, proj.Aggregator));
}
protected override Expression VisitSelect(SelectExpression select)
{
select = (SelectExpression)base.VisitSelect(select);
if (select.Skip != null)
{
SelectExpression newSelect = select.SetSkip(null).SetTake(null);
bool canAddColumn = !select.IsDistinct && (select.GroupBy == null || select.GroupBy.Count == 0);
if (!canAddColumn)
{
newSelect = newSelect.AddRedundantSelect(language, new TableAlias());
}
QueryType colType = language.TypeSystem.GetColumnType(typeof(int));
newSelect = newSelect.AddColumn(new ColumnDeclaration("_rownum", new RowNumberExpression(select.OrderBy), colType));
// add layer for WHERE clause that references new rownum column
newSelect = newSelect.AddRedundantSelect(language, new TableAlias());
newSelect = newSelect.RemoveColumn(newSelect.Columns.Single(c => c.Name == "_rownum"));
TableAlias newAlias = ((SelectExpression)newSelect.From).Alias;
var rnCol = new ColumnExpression(typeof(int), colType, newAlias, "_rownum");
Expression where;
if (select.Take != null)
{
where = new BetweenExpression(rnCol, Expression.Add(select.Skip, Expression.Constant(1)), Expression.Add(select.Skip, select.Take));
}
else
{
where = rnCol.GreaterThan(select.Skip);
}
if (newSelect.Where != null)
{
where = newSelect.Where.And(where);
}
newSelect = newSelect.SetWhere(where);
select = newSelect;
}
return(select);
}
