Skip to content

Commit

Permalink
Optimize computing reverse reindexing
Browse files Browse the repository at this point in the history 
We used to compute reverse count indexes twice while reindexing.
First, while computing reverse edges, and then later while explicitly
computing reverse count index. Now, we use a different function
while reindexing reverse edges and do not compute the reverse
count indexes.
  • Loading branch information
@mangalaman93
mangalaman93 committed Feb 14, 2020
1 parent e96fb63 commit 1e92791
Show file tree
Hide file tree
Showing 2 changed files with 105 additions and 12 deletions.
68 changes: 68 additions & 0 deletions dgraph/cmd/alpha/reindex_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -117,3 +117,71 @@ func TestReindexLang(t *testing.T) {
}
}`, res)
}

func TestReindexReverseCount(t *testing.T) {
require.NoError(t, dropAll())
require.NoError(t, alterSchema(`value: [uid] .`))

m1 := `{
set {
<1> <value> <4> .
<1> <value> <5> .
<1> <value> <6> .
<1> <value> <7> .
<1> <value> <8> .
<2> <value> <4> .
<2> <value> <5> .
<2> <value> <6> .
<3> <value> <5> .
<3> <value> <6> .
}
}`
_, err := mutationWithTs(m1, "application/rdf", false, true, 0)
require.NoError(t, err)

// reindex
require.NoError(t, alterSchema(`value: [uid] @count @reverse .`))

q1 := `{
q(func: eq(count(~value), "3")) {
uid
}
}`
res, _, err := queryWithTs(q1, "application/graphql+-", "", 0)
require.NoError(t, err)
require.JSONEq(t, `{
"data": {
"q": [
{
"uid": "0x5"
},
{
"uid": "0x6"
}
]
}
}`, res)

// adding another triplet
m2 := `{ set { <9> <value> <4> . }}`
_, err = mutationWithTs(m2, "application/rdf", false, true, 0)
require.NoError(t, err)

res, _, err = queryWithTs(q1, "application/graphql+-", "", 0)
require.NoError(t, err)
require.JSONEq(t, `{
"data": {
"q": [
{
"uid": "0x4"
},
{
"uid": "0x5"
},
{
"uid": "0x6"
}
]
}
}`, res)
}
49 changes: 37 additions & 12 deletions posting/index.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -172,6 +172,30 @@ func (txn *Txn) addReverseMutationHelper(ctx context.Context, plist *List,
}

func (txn *Txn) addReverseMutation(ctx context.Context, t *pb.DirectedEdge) error {
key := x.ReverseKey(t.Attr, t.ValueId)
plist, err := txn.GetFromDelta(key)
if err != nil {
return err
}
x.AssertTrue(plist != nil)

// We must create a copy here.
edge := &pb.DirectedEdge{
Entity: t.ValueId,
ValueId: t.Entity,
Attr: t.Attr,
Op: t.Op,
Facets: t.Facets,
}
if err := plist.addMutation(ctx, txn, edge); err != nil {
return err
}

ostats.Record(ctx, x.NumEdges.M(1))
return nil
}

func (txn *Txn) addReverseAndCountMutation(ctx context.Context, t *pb.DirectedEdge) error {
key := x.ReverseKey(t.Attr, t.ValueId)
hasCountIndex := schema.State().HasCount(t.Attr)

Expand Down Expand Up @@ -231,7 +255,7 @@ func (l *List) handleDeleteAll(ctx context.Context, edge *pb.DirectedEdge,
case isReversed:
// Delete reverse edge for each posting.
delEdge.ValueId = p.Uid
return txn.addReverseMutation(ctx, delEdge)
return txn.addReverseAndCountMutation(ctx, delEdge)
case isIndexed:
// Delete index edge of each posting.
val := types.Val{
Expand Down Expand Up @@ -282,7 +306,6 @@ func (txn *Txn) addCountMutation(ctx context.Context, t *pb.DirectedEdge, count
}
ostats.Record(ctx, x.NumEdges.M(1))
return nil

}

func (txn *Txn) updateCount(ctx context.Context, params countParams) error {
Expand All @@ -291,9 +314,11 @@ func (txn *Txn) updateCount(ctx context.Context, params countParams) error {
Attr: params.attr,
Op: pb.DirectedEdge_DEL,
}
if err := txn.addCountMutation(ctx, &edge, uint32(params.countBefore),
params.reverse); err != nil {
return err
if params.countBefore > 0 {
if err := txn.addCountMutation(ctx, &edge, uint32(params.countBefore),
params.reverse); err != nil {
return err
}
}

if params.countAfter > 0 {
Expand Down Expand Up @@ -431,7 +456,7 @@ func (l *List) AddMutationWithIndex(ctx context.Context, edge *pb.DirectedEdge,
// Add reverse mutation irrespective of hasMutated, server crash can happen after
// mutation is synced and before reverse edge is synced
if (pstore != nil) && (edge.ValueId != 0) && schema.State().IsReversed(edge.Attr) {
if err := txn.addReverseMutation(ctx, edge); err != nil {
if err := txn.addReverseAndCountMutation(ctx, edge); err != nil {
return err
}
}
Expand Down Expand Up @@ -533,14 +558,12 @@ func (r *rebuilder) Run(ctx context.Context) error {
dbOpts := badger.DefaultOptions(tmpIndexDir).
WithSyncWrites(false).
WithNumVersionsToKeep(math.MaxInt64).
WithLogger(&x.ToGlog{}).
WithCompression(options.None).
WithEventLogging(false).
WithLogRotatesToFlush(10).
WithMaxCacheSize(50) // TODO(Aman): Disable cache altogether

// TODO(Ibrahim): Remove this once badger is updated.
dbOpts.ZSTDCompressionLevel = 1

tmpDB, err := badger.OpenManaged(dbOpts)
if err != nil {
return errors.Wrap(err, "error opening temp badger for reindexing")
Expand All @@ -558,9 +581,6 @@ func (r *rebuilder) Run(ctx context.Context) error {
// Todo(Aman): Replace TxnWriter with WriteBatch. While we do that we should ensure that
// WriteBatch has a mechanism for throttling. Also, find other places where TxnWriter
// could be replaced with WriteBatch in the code
// Todo(Aman): Replace TxnWriter with WriteBatch. While we do that we should ensure that
// WriteBatch has a mechanism for throttling. Also, find other places where TxnWriter
// could be replaced with WriteBatch in the code.
tmpWriter := NewTxnWriter(tmpDB)
stream := pstore.NewStreamAt(r.startTs)
stream.LogPrefix = fmt.Sprintf("Rebuilding index for predicate %s (1/2):", r.attr)
Expand All @@ -583,6 +603,9 @@ func (r *rebuilder) Run(ctx context.Context) error {
return nil, errors.Wrapf(err, "error reading posting list from disk")
}

// We are using different transactions in each call to KeyToList function. This could
// be a problem for computing reverse count indexes if deltas for same key are added
// in different transactions. Such a case doesn't occur for now.
txn := NewTxn(r.startTs)
if err := r.fn(pk.Uid, l, txn); err != nil {
return nil, err
Expand Down Expand Up @@ -1002,6 +1025,8 @@ func rebuildReverseEdges(ctx context.Context, rb *IndexRebuild) error {
edge.Label = pp.Label

for {
// we only need to build reverse index here.
// We will update the reverse count index separately.
err := txn.addReverseMutation(ctx, &edge)
switch err {
case ErrRetry:
Expand Down

0 comments on commit 1e92791

Please sign in to comment.