// Arthmentic Simplification:
/*
* +/- zero to a column, or multiply/divide a column by 1
*/
internal bool IsArithIdentity(ConstExpr lce, ConstExpr rce)
{
ConstExpr ve = lce != null ? lce : rce;
ColExpr ce = (children_[0] is ColExpr) ? (ColExpr)children_[0] : (children_[1] is ColExpr ? (ColExpr)children_[1] : null);
if (ce == null)
{
return(false);
}
if (!(TypeBase.IsNumberType(ve.type_) && TypeBase.IsNumberType(ce.type_)))
{
return(false);
}
if ((op_ == "+" || op_ == "-") && ve.IsZero())
{
return(true);
}
if ((op_ == "*" || op_ == "/") && ve.IsOne())
{
return(true);
}
return(false);
}
public static ColExpr Load(XmlElement xml)
{
ColExpr res = new ColExpr();
res.Expression = xml.GetAttribute("expr");
res.Name = xml.GetAttribute("name");
switch (xml.GetAttribute("type"))
{
case "column":
res.Type = new ColumnColExprType();
break;
case "python":
res.Type = new PythonColExprType();
break;
case "null":
res.Type = new NullColExprType();
break;
case "const":
res.Type = new ConstColExprType();
break;
case "rownum":
res.Type = new RowNumberColExprType();
break;
default:
throw new InternalError("DAE-00024 Unknown col expr type:" + xml.GetAttribute("type"));
}
return(res);
}
public override void LoadFromXml(XmlElement xml, ITableStructure source, ITableStructure target)
{
m_source = source;
m_target = target;
if (xml.SelectSingleNode("Script") != null)
{
m_script = xml.SelectSingleNode("Script").InnerText;
}
TableStructure t = new TableStructure();
foreach (XmlElement e in xml.SelectNodes("Column"))
{
ColExpr ce = ColExpr.Load(e);
m_dstcols.Add(ce);
t.AddColumn(new ColumnStructure
{
ColumnName = ce.Name,
DataType = ce.GetColType(source)
}, true);
}
m_target = t;
UpdateFlags();
}
public static double EstSelectivity(this Expr filter)
{
var andorlist = filter.FilterToAndOrList();
double selectivity = filter is LogicAndExpr ? 1.0 : 0.0;
if (andorlist.Count == 1)
{
return(EstSingleSelectivity(filter));
}
else
{
// combine simple expressions of the same column
Dictionary <ColExpr, List <double> > colselcombine = new Dictionary <ColExpr, List <double> >();
foreach (var v in andorlist)
{
ColExpr col = ExtractColumn(v);
if (!(col is null))
{
if (colselcombine.ContainsKey(col))
{
colselcombine[col].Add(EstSelectivity(v));
}
else
{
colselcombine.Add(col, new List <double> {
EstSelectivity(v)
});
}
}
internal Expr SimplifyArithmetic(ConstExpr lve, ConstExpr rve)
{
// we know we have a BinExpr with numeric children
ConstExpr ve = lve != null ? lve : rve;
ColExpr ce = (children_[0] is ColExpr) ? (ColExpr)children_[0] : (children_[1] is ColExpr ? (ColExpr)children_[1] : null);
if (ce is null || ve is null)
{
return(this);
}
// Col + 0, or Col - 0 => return col
if ((op_ == "+" || op_ == "-") && ve.IsZero())
{
return(ce);
}
if ((op_ == "*" || op_ == "/") && ve.IsOne())
{
return(ce);
}
return(this);
}
