Allow setting interface{} value to posting list, and test it thoroughly

posting/list.go

@@ -69,6 +69,9 @@ func addTripleToPosting(b *flatbuffers.Builder,
 
 	var bo flatbuffers.UOffsetT
 	if t.Value != nil {
+		if t.ValueId != math.MaxUint64 {
+			log.Fatal("This should have already been set by the caller.")
+		}
 		var buf bytes.Buffer
 		enc := gob.NewEncoder(&buf)
 		if err := enc.Encode(t.Value); err != nil {
@@ -81,14 +84,9 @@ func addTripleToPosting(b *flatbuffers.Builder,
 
 	types.PostingStart(b)
 	if bo > 0 {
-		// All triples with a value set, have the same uid. In other words,
-		// an (entity, attribute) can only have one interface{} value.
-		types.PostingAddUid(b, math.MaxUint64)
 		types.PostingAddValue(b, bo)
-
-	} else {
-		types.PostingAddUid(b, t.ValueId)
 	}
+	types.PostingAddUid(b, t.ValueId)
 	types.PostingAddSource(b, so)
 	types.PostingAddTs(b, t.Timestamp.UnixNano())
 	types.PostingAddOp(b, op)
@@ -131,6 +129,16 @@ func init() {
 		len(empty), len(emptyPosting))
 }
 
+func ParseValue(i interface{}, p types.Posting) error {
+	if p.ValueLength() == 0 {
+		return errors.New("No value found in posting")
+	}
+	var buf bytes.Buffer
+	buf.Write(p.ValueBytes())
+	dec := gob.NewDecoder(&buf)
+	return dec.Decode(i)
+}
+
 func (l *List) Init(key []byte, pstore, mstore *store.Store) {
 	l.mutex.Lock()
 	defer l.mutex.Unlock()
@@ -391,6 +399,13 @@ func (l *List) AddMutation(t x.Triple, op byte) error {
 	// a)		check if the entity exists in main posting list.
 	// 				- If yes, store the mutation.
 	// 				- If no, disregard this mutation.
+
+	// All triples with a value set, have the same uid. In other words,
+	// an (entity, attribute) can only have one interface{} value.
+	if t.Value != nil {
+		t.ValueId = math.MaxUint64
+	}
+
 	b := flatbuffers.NewBuilder(0)
 	muts := types.GetRootAsPostingList(l.mbuffer, 0)
 	var offsets []flatbuffers.UOffsetT

posting/list_test.go

@@ -19,6 +19,7 @@ package posting
 import (
 	"fmt"
 	"io/ioutil"
+	"math"
 	"os"
 	"testing"
 	"time"
@@ -54,7 +55,7 @@ func NewStore(t *testing.T) string {
 	return path
 }
 
-func TestAddTriple(t *testing.T) {
+func TestAddMutation(t *testing.T) {
 	var l List
 	key := store.Key("name", 1)
 	pdir := NewStore(t)
@@ -189,10 +190,60 @@ func TestAddTriple(t *testing.T) {
 	if err := checkUids(t, dl, uids...); err != nil {
 		t.Error(err)
 	}
+}
 
+func TestAddMutation_Value(t *testing.T) {
 	var ol List
+	key := store.Key("value", 10)
+	pdir := NewStore(t)
+	defer os.RemoveAll(pdir)
+	ps := new(store.Store)
+	ps.Init(pdir)
+
+	mdir := NewStore(t)
+	defer os.RemoveAll(mdir)
+	ms := new(store.Store)
+	ms.Init(mdir)
+
 	ol.Init(key, ps, ms)
-	if err := checkUids(t, ol, uids...); err != nil {
+
+	triple := x.Triple{
+		Value:     "oh hey there",
+		Source:    "new-testing",
+		Timestamp: time.Now(),
+	}
+	if err := ol.AddMutation(triple, Set); err != nil {
+		t.Error(err)
+	}
+	var p types.Posting
+	ol.Get(&p, 0)
+	if p.Uid() != math.MaxUint64 {
+		t.Errorf("All value uids should go to MaxUint64. Got: %v", p.Uid())
+	}
+	var out string
+	if err := ParseValue(&out, p); err != nil {
+		t.Error(err)
+	}
+	if out != "oh hey there" {
+		t.Errorf("Expected a value. Got: [%q]", out)
+	}
+
+	// The value made it to the posting list. Changing it now.
+	triple.Value = 119
+	if err := ol.AddMutation(triple, Set); err != nil {
 		t.Error(err)
 	}
+	if ol.Length() != 1 {
+		t.Errorf("Length should be one. Got: %v", ol.Length())
+	}
+	if ok := ol.Get(&p, 0); !ok {
+		t.Error("While retrieving posting")
+	}
+	var iout int
+	if err := ParseValue(&iout, p); err != nil {
+		t.Error(err)
+	}
+	if iout != 119 {
+		t.Errorf("Expected 119. Got: %v", iout)
+	}
 }