Merge pull request #153 from mataevs/exceptop

Except/Not Operator for Gremlin.

query/gremlin/build_iterator.go

@@ -298,6 +298,21 @@ func buildIteratorTreeHelper(obj *otto.Object, qs graph.QuadStore, base graph.It
 		it = buildIteratorTreeHelper(arg.Object(), qs, subIt)
 	case "in":
 		it = buildInOutIterator(obj, qs, subIt, true)
+	case "except":
+		arg, _ := obj.Get("_gremlin_values")
+		firstArg, _ := arg.Object().Get("0")
+		if !isVertexChain(firstArg.Object()) {
+			return iterator.NewNull()
+		}
+
+		allIt := qs.NodesAllIterator()
+		toComplementIt := buildIteratorTree(firstArg.Object(), qs)
+		notIt := iterator.NewNot(toComplementIt, allIt)
+
+		and := iterator.NewAnd()
+		and.AddSubIterator(subIt)
+		and.AddSubIterator(notIt)
+		it = and
 	}
 	return it
 }

query/gremlin/gremlin_test.go

@@ -120,6 +120,20 @@ var testQueries = []struct {
 		tag:    "acd",
 		expect: []string{"D"},
 	},
+	{
+		message: "use Except to filter out a single vertex",
+		query: `
+			g.V("A", "B").Except(g.V("A")).All()
+		`,
+		expect: []string{"B"},
+	},
+	{
+		message: "use chained Except",
+		query: `
+			g.V("A", "B", "C").Except(g.V("B")).Except(g.V("C")).All()
+		`,
+		expect: []string{"A"},
+	},
 
 	// Morphism tests.
 	{

query/gremlin/traversals.go

@@ -38,6 +38,8 @@ func (wk *worker) embedTraversals(env *otto.Otto, obj *otto.Object) {
 	obj.Set("Has", wk.gremlinFunc("has", obj, env))
 	obj.Set("Save", wk.gremlinFunc("save", obj, env))
 	obj.Set("SaveR", wk.gremlinFunc("saver", obj, env))
+	obj.Set("Except", wk.gremlinFunc("except", obj, env))
+	obj.Set("Difference", wk.gremlinFunc("except", obj, env))
 }
 
 func (wk *worker) gremlinFunc(kind string, prev *otto.Object, env *otto.Otto) func(otto.FunctionCall) otto.Value {