Move Size handling out of Base

graph/iterator/hasa_iterator.go

@@ -240,3 +240,7 @@ func (it *HasA) Close() {
 
 // Register this iterator as a HasA.
 func (it *HasA) Type() graph.Type { return graph.HasA }
+
+func (it *HasA) Size() (int64, bool) {
+	return 0, true
+}

graph/iterator/iterator.go

@@ -80,11 +80,6 @@ func (it *Base) Result() graph.Value {
 	return it.Last
 }
 
-// If you're empty and you know it, clap your hands.
-func (it *Base) Size() (int64, bool) {
-	return 0, true
-}
-
 // Accessor
 func (it *Base) CanNext() bool { return it.canNext }
 

graph/iterator/linksto_iterator.go

@@ -200,3 +200,7 @@ func (it *LinksTo) Stats() graph.IteratorStats {
 		Size:      fanoutFactor * subitStats.Size,
 	}
 }
+
+func (it *LinksTo) Size() (int64, bool) {
+	return 0, true
+}

graph/iterator/optional_iterator.go

@@ -151,3 +151,8 @@ func (it *Optional) Stats() graph.IteratorStats {
 		Size:      subStats.Size,
 	}
 }
+
+// If you're empty and you know it, clap your hands.
+func (it *Optional) Size() (int64, bool) {
+	return 0, true
+}

graph/iterator/value_comparison_iterator.go

@@ -212,3 +212,7 @@ func (it *Comparison) Optimize() (graph.Iterator, bool) {
 func (it *Comparison) Stats() graph.IteratorStats {
 	return it.subIt.Stats()
 }
+
+func (it *Base) Size() (int64, bool) {
+	return 0, true
+}