diff --git a/graph/bolt/quadstore.go b/graph/bolt/quadstore.go
index 16bf75a..08ceb69 100644
--- a/graph/bolt/quadstore.go
+++ b/graph/bolt/quadstore.go
@@ -136,18 +136,28 @@ func bucketFor(d [4]quad.Direction) []byte {
 	return []byte{d[0].Prefix(), d[1].Prefix(), d[2].Prefix(), d[3].Prefix()}
 }
 
+func hashOf(s string) []byte {
+	h := hashPool.Get().(hash.Hash)
+	h.Reset()
+	defer hashPool.Put(h)
+	key := make([]byte, 0, hashSize)
+	h.Write([]byte(s))
+	key = h.Sum(key)
+	return key
+}
+
 func (qs *QuadStore) createKeyFor(d [4]quad.Direction, q quad.Quad) []byte {
 	key := make([]byte, 0, (hashSize * 4))
-	key = append(key, qs.hashOf(q.Get(d[0]))...)
-	key = append(key, qs.hashOf(q.Get(d[1]))...)
-	key = append(key, qs.hashOf(q.Get(d[2]))...)
-	key = append(key, qs.hashOf(q.Get(d[3]))...)
+	key = append(key, hashOf(q.Get(d[0]))...)
+	key = append(key, hashOf(q.Get(d[1]))...)
+	key = append(key, hashOf(q.Get(d[2]))...)
+	key = append(key, hashOf(q.Get(d[3]))...)
 	return key
 }
 
 func (qs *QuadStore) createValueKeyFor(s string) []byte {
 	key := make([]byte, 0, hashSize)
-	key = append(key, qs.hashOf(s)...)
+	key = append(key, hashOf(s)...)
 	return key
 }
 
@@ -379,16 +389,6 @@ func (qs *QuadStore) Quad(k graph.Value) quad.Quad {
 	return q
 }
 
-func (qs *QuadStore) hashOf(s string) []byte {
-	h := hashPool.Get().(hash.Hash)
-	h.Reset()
-	defer hashPool.Put(h)
-	key := make([]byte, 0, hashSize)
-	h.Write([]byte(s))
-	key = h.Sum(key)
-	return key
-}
-
 func (qs *QuadStore) ValueOf(s string) graph.Value {
 	return &Token{
 		bucket: nodeBucket,
diff --git a/graph/leveldb/quadstore.go b/graph/leveldb/quadstore.go
index c140277..828ab46 100644
--- a/graph/leveldb/quadstore.go
+++ b/graph/leveldb/quadstore.go
@@ -146,21 +146,31 @@ func (qa *QuadStore) createDeltaKeyFor(d graph.Delta) []byte {
 	return key
 }
 
+func hashOf(s string) []byte {
+	h := hashPool.Get().(hash.Hash)
+	h.Reset()
+	defer hashPool.Put(h)
+	key := make([]byte, 0, hashSize)
+	h.Write([]byte(s))
+	key = h.Sum(key)
+	return key
+}
+
 func (qs *QuadStore) createKeyFor(d [4]quad.Direction, q quad.Quad) []byte {
 	key := make([]byte, 0, 2+(hashSize*3))
 	// TODO(kortschak) Remove dependence on String() method.
 	key = append(key, []byte{d[0].Prefix(), d[1].Prefix()}...)
-	key = append(key, qs.hashOf(q.Get(d[0]))...)
-	key = append(key, qs.hashOf(q.Get(d[1]))...)
-	key = append(key, qs.hashOf(q.Get(d[2]))...)
-	key = append(key, qs.hashOf(q.Get(d[3]))...)
+	key = append(key, hashOf(q.Get(d[0]))...)
+	key = append(key, hashOf(q.Get(d[1]))...)
+	key = append(key, hashOf(q.Get(d[2]))...)
+	key = append(key, hashOf(q.Get(d[3]))...)
 	return key
 }
 
 func (qs *QuadStore) createValueKeyFor(s string) []byte {
 	key := make([]byte, 0, 1+hashSize)
 	key = append(key, []byte("z")...)
-	key = append(key, qs.hashOf(s)...)
+	key = append(key, hashOf(s)...)
 	return key
 }
 
@@ -347,16 +357,6 @@ func (qs *QuadStore) Quad(k graph.Value) quad.Quad {
 	return q
 }
 
-func (qs *QuadStore) hashOf(s string) []byte {
-	h := hashPool.Get().(hash.Hash)
-	h.Reset()
-	defer hashPool.Put(h)
-	key := make([]byte, 0, hashSize)
-	h.Write([]byte(s))
-	key = h.Sum(key)
-	return key
-}
-
 func (qs *QuadStore) ValueOf(s string) graph.Value {
 	return Token(qs.createValueKeyFor(s))
 }
diff --git a/graph/mongo/quadstore.go b/graph/mongo/quadstore.go
index b4e6fd5..12e6400 100644
--- a/graph/mongo/quadstore.go
+++ b/graph/mongo/quadstore.go
@@ -102,14 +102,14 @@ func newQuadStore(addr string, options graph.Options) (graph.QuadStore, error) {
 }
 
 func (qs *QuadStore) getIdForQuad(t quad.Quad) string {
-	id := qs.hashOf(t.Subject)
-	id += qs.hashOf(t.Predicate)
-	id += qs.hashOf(t.Object)
-	id += qs.hashOf(t.Label)
+	id := hashOf(t.Subject)
+	id += hashOf(t.Predicate)
+	id += hashOf(t.Object)
+	id += hashOf(t.Label)
 	return id
 }
 
-func (qs *QuadStore) hashOf(s string) string {
+func hashOf(s string) string {
 	h := hashPool.Get().(hash.Hash)
 	h.Reset()
 	defer hashPool.Put(h)
@@ -288,7 +288,7 @@ func (qs *QuadStore) QuadsAllIterator() graph.Iterator {
 }
 
 func (qs *QuadStore) ValueOf(s string) graph.Value {
-	return qs.hashOf(s)
+	return hashOf(s)
 }
 
 func (qs *QuadStore) NameOf(v graph.Value) string {