static ColumnType externalType2ColumnType(Type type)
{
ColumnType ctype;
if (type == typeof(double))
{
ctype = new DoubleType();
}
else if (type == typeof(int))
{
ctype = new IntType();
}
else if (type == typeof(string))
{
ctype = new VarCharType(64 * 1024);
}
else
{
throw new NotImplementedException();
}
return(ctype);
}
// during type coerse, we may have to change el/er type. Consider this case:
// el+er where el= 2.5 double, er = 10 decimal
// their result is decimal as decimal has higher precedence so we have to
// convert el to decimal to avoid later operator+ suprise.
//
public static ColumnType CoerseType(string op, Expr el, Expr er)
{
ColumnType result = null;
ColumnType l = el.type_;
ColumnType r = er.type_;
if (l.Equals(r))
{
return(l);
}
else
{
Type coertype = TypeBase.HigherPrecedence(l, r);
// these types needs precision etc further handling
if (coertype == typeof(NumericType))
{
if (l is DoubleType && r is NumericType rnum)
{
result = new NumericType(rnum.len_, rnum.scale_);
el.type_ = result;
if (el is ConstExpr ell)
{
ell.val_ = Convert.ToDecimal(ell.val_);
}
}
else if (r is DoubleType && l is NumericType lnum)
{
result = new NumericType(lnum.len_, lnum.scale_);
er.type_ = result;
if (er is ConstExpr erl)
{
erl.val_ = Convert.ToDecimal(erl.val_);
}
}
else if (l is NumericType || r is NumericType)
{
// FIXME: this is a rough calculation
int prec = 0, scale = 0;
if (l is NumericType ln)
{
prec = ln.len_; scale = ln.scale_;
}
if (r is NumericType rn)
{
prec = Math.Max(rn.len_, prec);
scale = Math.Max(rn.scale_, scale);
}
result = new NumericType(prec, scale);
}
}
else if (TypeBase.IsStringType(l) && TypeBase.IsStringType(r))
{
result = new VarCharType(Int32.MaxValue);
}
else
{
result = (ColumnType)Activator.CreateInstance(coertype);
}
}
Debug.Assert(result != null);
return(result);
}