// --- create ------------------------------------------------------
// from existing columns, with normalisation by default
public static DataHeading Create(IEnumerable <DataColumn> columns, bool istuple = true)
{
Logger.Assert(columns != null && columns.All(c => c.DataType.IsVariable), "bad columns");
var dh = new DataHeading()
{
_columns = columns.ToArray(),
IsTuple = istuple,
};
dh._coldict = Enumerable.Range(0, dh._columns.Length)
.ToDictionary(x => dh._columns[x].Name, x => x);
return((istuple) ? DataTypeTuple.Get(dh).Heading : dh);
}
// construct a type from a base name, optional heading and optional user type name
public static DataType Derive(DataType basetype, DataHeading heading, string username)
{
if (basetype == DataTypes.Table)
{
return(DataTypeRelation.Get(heading));
}
if (basetype == DataTypes.Row)
{
return(DataTypeTuple.Get(heading));
}
if (basetype == DataTypes.User)
{
return(DataTypeUser.Get(username, heading.Columns));
}
return(basetype);
}
// Get type from dictionary, or create and add
// Every relation needs a row type, so make sure they use the same heading
public static DataTypeRelation Get(DataHeading heading)
{
if (_headings.ContainsKey(heading))
{
return(_headings[heading]);
}
var tupletype = DataTypeTuple.Get(heading);
var dt = DataTypeRelation.Create("relation", tupletype.Heading, TypeFlags.Variable | TypeFlags.Generated | TypeFlags.HasHeading);
dt.Ordinal = _headings.Count + 1;
dt.ChildTupleType = tupletype;
dt.NativeType = TypeMaker.CreateType(dt);
_headings[heading] = dt;
var x = Activator.CreateInstance(dt.NativeType);
return(dt);
}
// Create a row that belongs to a table.
// Can be called with a tuple or non-tuple heading. If the latter, reorder values to match tuple heading.
public static DataRow Create(DataHeading heading, TypedValue[] values)
{
if (values.Length != heading.Degree)
{
throw new ArgumentOutOfRangeException("values", "wrong degree");
}
Logger.Assert(values.All(v => v != null), "null value");
var newheading = (heading.IsTuple) ? heading : DataTypeTuple.Get(heading).Heading;
var dr = new DataRow()
{
DataType = DataTypeTuple.Get(heading),
Heading = newheading,
_values = (heading.IsTuple) ? values : newheading.Columns.Select(c => values[heading.FindIndex(c)]).ToArray(),
};
dr._hashcode = dr.CalcHashCode();
dr.Heading.CheckValues(dr.Values);
return(dr);
}