|
public ChangeColumns ( IEnumerable |
||
| columns | IEnumerable |
|
| return | ||
protected override Expression VisitSelect(SqlSelectExpression selectExpression)
{
List<SqlColumnDeclaration> newColumns = null;
for (var i = 0; i < selectExpression.Columns.Count; i++)
{
var column = selectExpression.Columns[i];
var visitedColumnExpression = this.Visit(column.Expression);
if (visitedColumnExpression.Type.GetUnwrappedNullableType() == typeof(bool) && !(visitedColumnExpression is BitBooleanExpression))
{
if (newColumns == null)
{
newColumns = new List<SqlColumnDeclaration>(selectExpression.Columns.Take(i));
}
var newColumnExpression = BitBooleanExpression.Coerce(visitedColumnExpression);
var newColumnDeclaration = new SqlColumnDeclaration(column.Name, newColumnExpression);
newColumns.Add(newColumnDeclaration);
}
else if (visitedColumnExpression != column.Expression)
{
if (newColumns == null)
{
newColumns = new List<SqlColumnDeclaration>(selectExpression.Columns.Take(i));
}
newColumns.Add(column.ReplaceExpression(visitedColumnExpression));
}
else if (newColumns != null)
{
newColumns.Add(column);
}
}
var where = this.Visit(selectExpression.Where);
if ((where is BitBooleanExpression))
{
where = Expression.Equal(where, Expression.Constant(true));
}
if (where != selectExpression.Where)
{
if (newColumns != null)
{
return selectExpression.ChangeWhereAndColumns(where, new ReadOnlyList<SqlColumnDeclaration>(newColumns));
}
else
{
return selectExpression.ChangeWhere(where);
}
}
else if (newColumns != null)
{
return selectExpression.ChangeColumns(newColumns, true);
}
else
{
return base.VisitSelect(selectExpression);
}
}
protected override Expression VisitSelect(SqlSelectExpression select)
{
var columnRemoved = false;
select = (SqlSelectExpression)base.VisitSelect(select);
var columnsOrderedByName = select.Columns.OrderBy(c => c.Name).ToList();
var removedColumns = new BitArray(select.Columns.Count);
for (int i = 0, n = columnsOrderedByName.Count; i < n - 1; i++)
{
var icolumn = columnsOrderedByName[i];
var iNewColumnExpression = new SqlColumnExpression(icolumn.Expression.Type, select.Alias, icolumn.Name);
for (var j = i + 1; j < n; j++)
{
if (!removedColumns.Get(j))
{
var jcolumn = columnsOrderedByName[j];
if (IsSameExpression(icolumn.Expression, jcolumn.Expression))
{
// 'j' references should now be a reference to 'i'
var jNewColumnExpression = new SqlColumnExpression(jcolumn.Expression.Type, select.Alias, jcolumn.Name);
this.visitedColumns.Add(jNewColumnExpression, iNewColumnExpression);
removedColumns.Set(j, true);
columnRemoved = true;
}
}
}
}
if (columnRemoved)
{
var newColumnDeclarations = new List<SqlColumnDeclaration>();
for (int i = 0, n = columnsOrderedByName.Count; i < n; i++)
{
if (!removedColumns.Get(i))
{
newColumnDeclarations.Add(columnsOrderedByName[i]);
}
}
select = select.ChangeColumns(newColumnDeclarations);
}
return select;
}
