Golang posting.GetOrCreate函數代碼示例

func (s *state) handleNQuads(wg *sync.WaitGroup) {
	for nq := range s.cnq {
		if farm.Fingerprint64([]byte(nq.Subject))%s.mod != 0 {
			// Ignore due to mod sampling.
			atomic.AddUint64(&s.ctr.ignored, 1)
			continue
		}

		edge, err := nq.ToEdge()
		for err != nil {
			// Just put in a retry loop to tackle temporary errors.
			if err == posting.E_TMP_ERROR {
				time.Sleep(time.Microsecond)

			} else {
				glog.WithError(err).WithField("nq", nq).
					Error("While converting to edge")
				return
			}
			edge, err = nq.ToEdge()
		}

		key := posting.Key(edge.Entity, edge.Attribute)
		plist := posting.GetOrCreate(key)
		plist.AddMutation(edge, posting.Set)
		atomic.AddUint64(&s.ctr.processed, 1)
	}
	wg.Done()
}

// allocateUniqueUid returns an integer in range:
// [minIdx, maxIdx] derived based on numInstances and instanceIdx.
// which hasn't already been allocated to other xids. It does this by
// taking the fingerprint of the xid appended with zero or more spaces
// until the obtained integer is unique.
func allocateUniqueUid(instanceIdx uint64, numInstances uint64) uint64 {
	mod := math.MaxUint64 / numInstances
	minIdx := instanceIdx * mod

	buf := make([]byte, 128)
	for {
		_, err := rand.Read(buf)
		x.Checkf(err, "rand.Read shouldn't throw an error")

		uidb := farm.Fingerprint64(buf) // Generate from hash.
		uid := (uidb % mod) + minIdx
		if uid == math.MaxUint64 || !lmgr.isNew(uid) {
			continue
		}

		// Check if this uid has already been allocated.
		key := x.DataKey("_uid_", uid)
		pl, decr := posting.GetOrCreate(key)
		defer decr()

		if pl.Length(0) == 0 {
			return uid
		}
	}
	log.Fatalf("This shouldn't be reached.")
	return 0
}

func (s *state) handleNQuads(wg *sync.WaitGroup) {
	for nq := range s.cnq {
		edge, err := nq.ToEdge(s.instanceIdx, s.numInstances)
		for err != nil {
			// Just put in a retry loop to tackle temporary errors.
			if err == posting.E_TMP_ERROR {
				time.Sleep(time.Microsecond)

			} else {
				glog.WithError(err).WithField("nq", nq).
					Error("While converting to edge")
				return
			}
			edge, err = nq.ToEdge(s.instanceIdx, s.numInstances)
		}

		// Only handle this edge if the attribute satisfies the modulo rule
		if farm.Fingerprint64([]byte(edge.Attribute))%s.numInstances ==
			s.instanceIdx {
			key := posting.Key(edge.Entity, edge.Attribute)
			plist := posting.GetOrCreate(key, dataStore)
			plist.AddMutation(edge, posting.Set)
			atomic.AddUint64(&s.ctr.processed, 1)
		} else {
			atomic.AddUint64(&s.ctr.ignored, 1)
		}

	}
	wg.Done()
}

func ExternalId(uid uint64) (xid string, rerr error) {
	key := posting.Key(uid, "_xid_") // uid -> "_xid_" -> xid
	pl := posting.GetOrCreate(key, uidStore)
	if pl.Length() == 0 {
		return "", errors.New("NO external id")
	}

	if pl.Length() > 1 {
		glog.WithField("uid", uid).Fatal("This shouldn't be happening.")
		return "", errors.New("Multiple external ids for this uid.")
	}

	var p types.Posting
	if ok := pl.Get(&p, 0); !ok {
		glog.WithField("uid", uid).Error("While retrieving posting")
		return "", errors.New("While retrieving posting")
	}

	if p.Uid() != math.MaxUint64 {
		glog.WithField("uid", uid).Fatal("Value uid must be MaxUint64.")
	}
	var t interface{}
	rerr = posting.ParseValue(&t, p.ValueBytes())
	xid = t.(string)
	return xid, rerr
}

func addEdgeToUID(t *testing.T, ps *store.Store, attr string, src uint64, dst uint64) {
	edge := &task.DirectedEdge{
		ValueId: dst,
		Label:   "testing",
		Attr:    attr,
		Entity:  src,
	}
	l, _ := posting.GetOrCreate(x.DataKey(attr, src))
	require.NoError(t,
		l.AddMutationWithIndex(context.Background(), edge, posting.Set))
}

func markTaken(ctx context.Context, uid uint64) {
	mu := &task.DirectedEdge{
		Entity: uid,
		Attr:   "_uid_",
		Value:  []byte("_"), // not txid
		Label:  "_loader_",
	}
	key := x.DataKey("_uid_", uid)
	plist, decr := posting.GetOrCreate(key)
	plist.AddMutation(ctx, mu, posting.Set)
	decr()
}

func addEdgeToTypedValue(t *testing.T, ps *store.Store, attr string, src uint64,
	typ types.TypeID, value []byte) {
	edge := &task.DirectedEdge{
		Value:     value,
		ValueType: uint32(typ),
		Label:     "testing",
		Attr:      attr,
		Entity:    src,
	}
	l, _ := posting.GetOrCreate(x.DataKey(attr, src))
	require.NoError(t,
		l.AddMutationWithIndex(context.Background(), edge, posting.Set))
}

// handleNQuads converts the nQuads that satisfy the modulo
// rule into posting lists.
func (s *state) handleNQuads(wg *sync.WaitGroup) {
	defer wg.Done()
	// Check if we need to mark used UIDs.
	markUids := s.groupsMap[group.BelongsTo("_uid_")]
	ctx := context.Background()
	for nq := range s.cnq {
		if s.Error() != nil {
			return
		}
		// Only handle this edge if the attribute satisfies the modulo rule
		if !s.groupsMap[group.BelongsTo(nq.Predicate)] {
			atomic.AddUint64(&s.ctr.ignored, 1)
			continue
		}

		edge, err := nq.ToEdge()
		for err != nil {
			// Just put in a retry loop to tackle temporary errors.
			if err == posting.ErrRetry {
				time.Sleep(time.Microsecond)

			} else {
				s.SetError(err)
				glog.WithError(err).WithField("nq", nq).
					Error("While converting to edge")
				return
			}
			edge, err = nq.ToEdge()
		}

		key := x.DataKey(edge.Attr, edge.Entity)

		plist, decr := posting.GetOrCreate(key)
		plist.AddMutationWithIndex(ctx, edge, posting.Set)
		decr() // Don't defer, just call because we're in a channel loop.

		// Mark UIDs and XIDs as taken
		if markUids {
			// Mark entity UID.
			markTaken(ctx, edge.Entity)
			// Mark the Value UID.
			if edge.ValueId != 0 {
				markTaken(ctx, edge.ValueId)
			}
		}
		atomic.AddUint64(&s.ctr.processed, 1)
	}
}

func ProcessTask(query []byte) (result []byte, rerr error) {
	uo := flatbuffers.GetUOffsetT(query)
	q := new(task.Query)
	q.Init(query, uo)

	b := flatbuffers.NewBuilder(0)
	voffsets := make([]flatbuffers.UOffsetT, q.UidsLength())
	uoffsets := make([]flatbuffers.UOffsetT, q.UidsLength())

	attr := string(q.Attr())
	for i := 0; i < q.UidsLength(); i++ {
		uid := q.Uids(i)
		key := posting.Key(uid, attr)
		pl := posting.GetOrCreate(key, dataStore)

		var valoffset flatbuffers.UOffsetT
		if val, err := pl.Value(); err != nil {
			valoffset = b.CreateByteVector(x.Nilbyte)
		} else {
			valoffset = b.CreateByteVector(val)
		}
		task.ValueStart(b)
		task.ValueAddVal(b, valoffset)
		voffsets[i] = task.ValueEnd(b)

		ulist := pl.GetUids()
		uoffsets[i] = x.UidlistOffset(b, ulist)
	}
	task.ResultStartValuesVector(b, len(voffsets))
	for i := len(voffsets) - 1; i >= 0; i-- {
		b.PrependUOffsetT(voffsets[i])
	}
	valuesVent := b.EndVector(len(voffsets))

	task.ResultStartUidmatrixVector(b, len(uoffsets))
	for i := len(uoffsets) - 1; i >= 0; i-- {
		b.PrependUOffsetT(uoffsets[i])
	}
	matrixVent := b.EndVector(len(uoffsets))

	task.ResultStart(b)
	task.ResultAddValues(b, valuesVent)
	task.ResultAddUidmatrix(b, matrixVent)
	rend := task.ResultEnd(b)
	b.Finish(rend)
	return b.Bytes[b.Head():], nil
}

func allocateUniqueUid(xid string, instanceIdx uint64,
	numInstances uint64) (uid uint64, rerr error) {

	mod := math.MaxUint64 / numInstances
	minIdx := instanceIdx * mod
	for sp := ""; ; sp += " " {
		txid := xid + sp

		uid1 := farm.Fingerprint64([]byte(txid)) // Generate from hash.
		uid = (uid1 % mod) + minIdx

		glog.WithField("txid", txid).WithField("uid", uid).Debug("Generated")
		if uid == math.MaxUint64 {
			glog.Debug("Hit uint64max while generating fingerprint. Ignoring...")
			continue
		}

		// Check if this uid has already been allocated.
		key := posting.Key(uid, "_xid_") // uid -> "_xid_" -> xid
		pl := posting.GetOrCreate(key, uidStore)

		if pl.Length() > 0 {
			// Something already present here.
			var p types.Posting
			pl.Get(&p, 0)

			var tmp interface{}
			posting.ParseValue(&tmp, p.ValueBytes())
			glog.Debug("Found existing xid: [%q]. Continuing...", tmp.(string))
			continue
		}

		// Uid hasn't been assigned yet.
		t := x.DirectedEdge{
			Value:     xid, // not txid
			Source:    "_assigner_",
			Timestamp: time.Now(),
		}
		rerr = pl.AddMutation(t, posting.Set)
		if rerr != nil {
			glog.WithError(rerr).Error("While adding mutation")
		}
		return uid, rerr
	}
	return 0, errors.New("Some unhandled route lead me here." +
		" Wake the stupid developer up.")
}

// runMutations goes through all the edges and applies them. It returns the
// mutations which were not applied in left.
func runMutations(ctx context.Context, edges []*task.DirectedEdge, op uint32) error {
	for _, edge := range edges {
		if !groups().ServesGroup(group.BelongsTo(edge.Attr)) {
			return x.Errorf("Predicate fingerprint doesn't match this instance")
		}

		key := x.DataKey(edge.Attr, edge.Entity)
		plist, decr := posting.GetOrCreate(key)
		defer decr()

		if err := plist.AddMutationWithIndex(ctx, edge, op); err != nil {
			x.Printf("Error while adding mutation: %v %v", edge, err)
			return err // abort applying the rest of them.
		}
	}
	return nil
}

func writePLs(t *testing.T, pred string, count int, vid uint64, ps *store.Store) {
	for i := 0; i < count; i++ {
		k := x.DataKey(pred, uint64(i))
		list, _ := posting.GetOrCreate(k)

		de := &task.DirectedEdge{
			ValueId: vid,
			Label:   "test",
		}
		list.AddMutation(context.TODO(), de, posting.Set)
		if merged, err := list.CommitIfDirty(context.TODO()); err != nil {
			t.Errorf("While merging: %v", err)
		} else if !merged {
			t.Errorf("No merge happened")
		}
	}
}

func GetOrAssign(xid string, instanceIdx uint64, numInstances uint64) (uid uint64, rerr error) {
	key := stringKey(xid)
	pl := posting.GetOrCreate(key)
	if pl.Length() == 0 {
		return assignNew(pl, xid, instanceIdx, numInstances)

	} else if pl.Length() > 1 {
		glog.Fatalf("We shouldn't have more than 1 uid for xid: %v\n", xid)

	} else {
		// We found one posting.
		var p types.Posting
		if ok := pl.Get(&p, 0); !ok {
			return 0, errors.New("While retrieving entry from posting list")
		}
		return p.Uid(), nil
	}
	return 0, errors.New("Some unhandled route lead me here." +
		" Wake the stupid developer up.")
}

// getPostingValue looks up key, gets the value, converts it. If any error is
// encountered, we return nil. This is used in some filtering where we do not
// want to waste time creating errors.
func getPostingValue(key []byte, scalarType types.Scalar) *types.Value {
	pl, decr := posting.GetOrCreate(key)
	defer decr()

	valBytes, vType, err := pl.Value()
	if bytes.Equal(valBytes, nil) {
		return nil
	}
	val := types.ValueForType(types.TypeID(vType))
	if val == nil {
		return nil
	}
	if err := val.UnmarshalBinary(valBytes); err != nil {
		return nil
	}
	// Convert to schema type.
	sv, err := scalarType.Convert(val)
	if err != nil {
		return nil
	}
	return &sv
}

// fetchValue gets the value for a given UID.
func fetchValue(uid uint64, attr string, scalar types.Scalar) (types.Value, error) {
	pl, decr := posting.GetOrCreate(x.DataKey(attr, uid))
	defer decr()

	valBytes, vType, err := pl.Value()
	if err != nil {
		return nil, err
	}
	val := types.ValueForType(types.TypeID(vType))
	if val == nil {
		return nil, x.Errorf("Invalid type: %v", vType)
	}
	err = val.UnmarshalBinary(valBytes)
	if err != nil {
		return nil, err
	}

	schemaVal, err := scalar.Convert(val)
	if err != nil {
		return nil, err
	}
	return schemaVal, nil
}