func (m *JobBuilder) VisitJoin(from *expr.SqlSource) (expr.Task, error) {
u.Debugf("VisitJoin %s", from.Source)
//u.Debugf("from.Name:'%v' : %v", from.Name, from.Source.String())
source := m.schema.Conn(from.SourceName())
//u.Debugf("left source: %T", source)
// Must provider either Scanner, SourcePlanner, Seeker interfaces
if sourcePlan, ok := source.(datasource.SourcePlanner); ok {
// This is flawed, visitor pattern would have you pass in a object which implements interface
// but is one of many different objects that implement that interface so that the
// Accept() method calls the apppropriate method
u.Warnf("SourcePlanner????")
scanner, err := sourcePlan.Accept(NewSourcePlan(from))
if err == nil {
return NewSourceJoin(from, scanner), nil
}
u.Errorf("Could not source plan for %v %T %#v", from.Name, source, source)
}
scanner, ok := source.(datasource.Scanner)
if !ok {
u.Errorf("Could not create scanner for %v %T %#v", from.Name, source, source)
return nil, fmt.Errorf("Must Implement Scanner")
}
if err := buildColIndex(scanner, from); err != nil {
return nil, err
}
return NewSourceJoin(from, scanner), nil
}
