protected virtual Expression VisitBetween(DbBetweenExpression between)
{
var expr = this.Visit(between.Expression);
var lower = this.Visit(between.Lower);
var upper = this.Visit(between.Upper);
return(this.UpdateBetween(between, expr, lower, upper));
}
protected virtual bool CompareBetween(DbBetweenExpression a, DbBetweenExpression b)
{
return
(
this.Compare(a.Expression, b.Expression) &&
this.Compare(a.Lower, b.Lower) &&
this.Compare(a.Upper, b.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 VisitBetween(DbBetweenExpression between)
{
this.VisitValue(between.Expression);
this.Write(" BETWEEN ");
this.VisitValue(between.Lower);
this.Write(" AND ");
this.VisitValue(between.Upper);
return(between);
}
protected override Expression VisitSelect(DbSelectExpression select)
{
select = base.VisitSelect(select) as DbSelectExpression;
if (select.Skip != null)
{
var newSelect = select.SetSkip(null).SetTake(null);
var canAddColumn = !select.IsDistinct && (select.GroupBy == null || select.GroupBy.Count == 0);
if (canAddColumn == false)
{
newSelect = newSelect.AddRedundantSelect(this.language, new TableAlias());
}
var colType = this.language.TypeSystem.GetColumnType(typeof(int));
newSelect = newSelect.AddColumn(new DbColumnDeclaration("_rownum", new DbRowNumberExpression(select.OrderBy), colType));
newSelect = newSelect.AddRedundantSelect(this.language, new TableAlias());
newSelect = newSelect.RemoveColumn(newSelect.Columns.Single(c => c.Name == "_rownum"));
var newAlias = (newSelect.From as DbSelectExpression).Alias;
var rnCol = new DbColumnExpression(typeof(int), colType, newAlias, "_rownum");
var where = null as Expression;
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);
}
