convert to prefix byte

graph/leveldb/triplestore.go

@@ -114,7 +114,7 @@ func (ts *TripleStore) Size() int64 {
 func (ts *TripleStore) createKeyFor(d [3]graph.Direction, triple *graph.Triple) []byte {
 	key := make([]byte, 0, 2+(ts.hasher.Size()*3))
 	// TODO(kortschak) Remove dependence on String() method.
-	key = append(key, []byte(d[0].Prefix()+d[1].Prefix())...)
+	key = append(key, []byte{d[0].Prefix(), d[1].Prefix()}...)
 	key = append(key, ts.convertStringToByteHash(triple.Get(d[0]))...)
 	key = append(key, ts.convertStringToByteHash(triple.Get(d[1]))...)
 	key = append(key, ts.convertStringToByteHash(triple.Get(d[2]))...)
@@ -124,7 +124,7 @@ func (ts *TripleStore) createKeyFor(d [3]graph.Direction, triple *graph.Triple)
 func (ts *TripleStore) createProvKeyFor(d [3]graph.Direction, triple *graph.Triple) []byte {
 	key := make([]byte, 0, 2+(ts.hasher.Size()*4))
 	// TODO(kortschak) Remove dependence on String() method.
-	key = append(key, []byte(graph.Provenance.Prefix()+d[0].Prefix())...)
+	key = append(key, []byte{graph.Provenance.Prefix(), d[0].Prefix()}...)
 	key = append(key, ts.convertStringToByteHash(triple.Get(graph.Provenance))...)
 	key = append(key, ts.convertStringToByteHash(triple.Get(d[0]))...)
 	key = append(key, ts.convertStringToByteHash(triple.Get(d[1]))...)

graph/triple.go

@@ -60,20 +60,20 @@ const (
 	Provenance
 )
 
-func (d Direction) Prefix() string {
+func (d Direction) Prefix() byte {
 	switch d {
 	case Any:
-		return "a"
+		return 'a'
 	case Subject:
-		return "s"
+		return 's'
 	case Predicate:
-		return "p"
+		return 'p'
 	case Provenance:
-		return "c"
+		return 'c'
 	case Object:
-		return "o"
+		return 'o'
 	default:
-		return fmt.Sprint("illegal direction:", byte(d))
+		return '\x00'
 	}
 }