// get the type of a relation from some persistence store
// Used during compilation or startup -- if successful, variable will be created with flags
// Then use AddRelvar to import the value
public DataType GetRelvarType(string source, string what)
{
var islinked = (source == DefaultDatabaseSource);
if (islinked)
{
if (SqlFlag)
{
var heading = SqlTarget.Current.GetTableHeading(what);
return((heading == null) ? null : DataTypeRelation.Get(heading));
}
else
{
var type = Persist.Create(DatabasePath, false).Peek(what);
return(type);
}
}
else
{
var heading = DataSourceStream.Create(source, SourcePath).Peek(what);
if (heading != null)
{
return(DataTypeRelation.Get(heading));
}
}
return(null);
}
// Get the value of a relation by importing some other format
// Entry previously created by peeking
public bool ImportRelvar(string source, string name, string what, string locator)
{
var entry = GlobalVars.FindEntry(name);
Logger.Assert(entry != null, name);
var heading = entry.DataType.Heading;
var stream = DataSourceStream.Create(source, locator);
var table = stream.Read(what, heading);
if (table == null || !heading.Equals(table.Heading))
{
throw ProgramError.Fatal("Catalog", "{0} table not found: '{1}'", source, stream.GetPath(what));
}
GlobalVars.SetValue(entry, RelationValue.Create(table));
return(true);
}
