Enumerate iterator types

graph/memstore/iterator.go

@@ -101,12 +101,18 @@ func (it *Iterator) DebugString(indent int) string {
 	return fmt.Sprintf("%s(%s tags:%s size:%d %s)", strings.Repeat(" ", indent), it.Type(), it.Tags(), size, it.data)
 }
 
-func (it *Iterator) Type() string {
-	return "llrb"
-}
-func (it *Iterator) Sorted() bool {
-	return true
+var memType graph.Type
+
+func init() {
+	memType = graph.Register("llrb")
 }
+
+func Type() graph.Type { return memType }
+
+func (it *Iterator) Type() graph.Type { return memType }
+
+func (it *Iterator) Sorted() bool { return true }
+
 func (it *Iterator) Optimize() (graph.Iterator, bool) {
 	return it, false
 }

graph/memstore/triplestore_iterator_optimize.go

@@ -21,7 +21,7 @@ import (
 
 func (ts *TripleStore) OptimizeIterator(it graph.Iterator) (graph.Iterator, bool) {
 	switch it.Type() {
-	case "linksto":
+	case graph.LinksTo:
 		return ts.optimizeLinksTo(it.(*iterator.LinksTo))
 
 	}
@@ -34,7 +34,7 @@ func (ts *TripleStore) optimizeLinksTo(it *iterator.LinksTo) (graph.Iterator, bo
 		return it, false
 	}
 	primary := subs[0]
-	if primary.Type() == "fixed" {
+	if primary.Type() == graph.Fixed {
 		size, _ := primary.Size()
 		if size == 1 {
 			val, ok := primary.Next()

graph/memstore/triplestore_test.go

@@ -105,7 +105,7 @@ func TestLinksToOptimization(t *testing.T) {
 	if !changed {
 		t.Error("Iterator didn't change")
 	}
-	if newIt.Type() != "llrb" {
+	if newIt.Type() != Type() {
 		t.Fatal("Didn't swap out to LLRB")
 	}
 	v := newIt.(*Iterator)