func (rv *RangeVar) OpenRelation() (rel *access.Relation, err error) {
/* TODO: Refactor this to RelnameGetOid() */
class_rel, err := access.HeapOpen(access.ClassRelId)
if err != nil {
return nil, err
}
defer class_rel.Close()
scankeys := []access.ScanKey{
{access.Anum_class_relname, system.Datum(rv.RelationName)},
}
scan, err := class_rel.BeginScan(scankeys)
if err != nil {
return nil, err
}
defer scan.EndScan()
tuple, err := scan.Next()
if err != nil {
return nil, errors.New("relation not found")
}
relid := tuple.Get(int32(1)).(system.Oid)
return access.HeapOpen(relid)
}
func HeapOpen(relid system.Oid) (*Relation, error) {
if relid == ClassRelId {
relation := &Relation{
RelId: relid,
RelName: "bp_class",
RelDesc: ClassTupleDesc,
}
return relation, nil
} else if relid == AttributeRelId {
relation := &Relation{
RelId: relid,
RelName: "bp_attribute",
RelDesc: AttributeTupleDesc,
}
return relation, nil
}
/*
* Collect class information. Currently, nothing but name is stored.
*/
class_rel, err := HeapOpen(ClassRelId)
if err != nil {
return nil, err
}
defer class_rel.Close()
var scan_keys []ScanKey
scan_keys = []ScanKey{
{Anum_class_oid, system.Datum(relid)},
}
class_scan, err := class_rel.BeginScan(scan_keys)
if err != nil {
return nil, err
}
defer class_scan.EndScan()
class_tuple, err := class_scan.Next()
relation := &Relation{
RelId: relid,
RelName: class_tuple.Get(2).(system.Name),
}
attr_rel, err := HeapOpen(AttributeRelId)
if err != nil {
return nil, err
}
defer attr_rel.Close()
scan_keys = []ScanKey{
{Anum_attribute_attrelid, system.Datum(relid)},
}
/*
* Collect attributes
*/
attr_scan, err := attr_rel.BeginScan(scan_keys)
if err != nil {
return nil, err
}
defer attr_scan.EndScan()
var attributes []*Attribute
for {
attr_tuple, err := attr_scan.Next()
if err != nil {
break
}
attribute := &Attribute{
AttName: attr_tuple.Get(Anum_attribute_attname).(system.Name),
AttType: attr_tuple.Get(Anum_attribute_atttype).(system.Oid),
}
attributes = append(attributes, attribute)
}
relation.RelDesc = &TupleDesc{
Attrs: attributes,
}
return relation, nil
}