protected virtual Expression VisitBetween(DbBetweenExpression between)
{
Expression expr = Visit(between.Expression);
Expression lower = Visit(between.Lower);
Expression upper = Visit(between.Upper);
return(UpdateBetween(between, expr, lower, upper));
}
protected DbBetweenExpression UpdateBetween(DbBetweenExpression between,
Expression expression, Expression lower, Expression upper)
{
if (expression != between.Expression ||
lower != between.Lower || upper != between.Upper)
{
return(new DbBetweenExpression(expression, lower, upper));
}
return(between);
}
protected override Expression VisitSelect(DbSelectExpression select)
{
select = (DbSelectExpression)base.VisitSelect(select);
if (select.Skip != null)
{
DbSelectExpression newSelect = select.SetSkip(null).SetTake(null);
bool canAddColumn = !select.IsDistinct && (select.GroupBy == null || select.GroupBy.Count == 0);
if (!canAddColumn)
{
newSelect = newSelect.AddRedundantSelect(new DbTableAlias());
}
newSelect = newSelect.AddColumn(new DbColumnDeclaration("rownum", new DbRowNumberExpression(select.OrderBy)));
// add layer for WHERE clause that references new rownum column
newSelect = newSelect.AddRedundantSelect(new DbTableAlias());
newSelect = newSelect.RemoveColumn(newSelect.Columns.Single(c => c.Name == "rownum"));
var newAlias = ((DbSelectExpression)newSelect.From).Alias;
DbColumnExpression rnCol = new DbColumnExpression(typeof(int), null, newAlias, "rownum");
Expression where;
if (select.Take != null)
{
where = new DbBetweenExpression(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;
}
protected override Expression VisitSelect(DbSelectExpression select)
{
select = (DbSelectExpression)base.VisitSelect(select);
if (select.Skip != null)
{
DbSelectExpression newSelect = select.SetSkip(null).SetTake(null);
bool canAddColumn = !select.IsDistinct && (select.GroupBy == null || select.GroupBy.Count == 0);
if (!canAddColumn)
{
newSelect = newSelect.AddRedundantSelect(new DbTableAlias());
}
newSelect = newSelect.AddColumn(new DbColumnDeclaration("rownum", new DbRowNumberExpression(select.OrderBy)));
// add layer for WHERE clause that references new rownum column
newSelect = newSelect.AddRedundantSelect(new DbTableAlias());
newSelect = newSelect.RemoveColumn(newSelect.Columns.Single(c => c.Name == "rownum"));
var newAlias = ((DbSelectExpression)newSelect.From).Alias;
DbColumnExpression rnCol = new DbColumnExpression(typeof(int), null, newAlias, "rownum");
Expression where;
if (select.Take != null)
{
where = new DbBetweenExpression(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);
}
protected DbBetweenExpression UpdateBetween(DbBetweenExpression between,
Expression expression, Expression lower, Expression upper)
{
if (expression != between.Expression ||
lower != between.Lower || upper != between.Upper)
return new DbBetweenExpression(expression, lower, upper);
return between;
}
protected virtual Expression VisitBetween(DbBetweenExpression between)
{
Expression expr = Visit(between.Expression);
Expression lower = Visit(between.Lower);
Expression upper = Visit(between.Upper);
return UpdateBetween(between, expr, lower, upper);
}
protected virtual bool CompareBetween(DbBetweenExpression a, DbBetweenExpression b)
{
return(Compare(a.Expression, b.Expression) &&
Compare(a.Lower, b.Lower) &&
Compare(a.Upper, b.Upper));
}
protected override Expression VisitBetween(DbBetweenExpression between)
{
this.VisitValue(between.Expression);
this.Write(" BETWEEN ");
this.VisitValue(between.Lower);
this.Write(" AND ");
this.VisitValue(between.Upper);
return between;
}
protected virtual bool CompareBetween(DbBetweenExpression a, DbBetweenExpression b)
{
return Compare(a.Expression, b.Expression)
&& Compare(a.Lower, b.Lower)
&& Compare(a.Upper, b.Upper);
}
