/go/libraries/doltcore/{doltdb,env}: another optimization

go/libraries/doltcore/doltdb/doltdb.go

@@ -88,6 +88,13 @@ type DoltDB struct {
 	databaseName string
 }
 
+type TagRefWithMeta struct {
+	TagRef        ref.TagRef
+	Meta          *datas.TagMeta
+	CommitAddr    hash.Hash
+	MaybeHeadAddr hash.Hash
+}
+
 // DoltDBFromCS creates a DoltDB from a noms chunks.ChunkStore
 func DoltDBFromCS(cs chunks.ChunkStore, databaseName string) *DoltDB {
 	vrw := types.NewValueStore(cs)
@@ -594,8 +601,13 @@ func (ddb *DoltDB) ResolveTag(ctx context.Context, tagRef ref.TagRef) (*Tag, err
 	return NewTag(ctx, tagRef.GetPath(), ds, ddb.vrw, ddb.ns)
 }
 
+// ResolveTag takes a TagRef and returns the corresponding Tag object.
+func (ddb *DoltDB) ResolveTagFromTagRefWithMeta(ctx context.Context, tagRefWithMeta *TagRefWithMeta) (*Tag, error) {
+	return NewTagFromTagRefWithMeta(ctx, tagRefWithMeta.TagRef.GetPath(), tagRefWithMeta, ddb.vrw, ddb.ns)
+}
+
 // ResolveTagMeta takes a TagRef and returns the corresponding TagMeta object.
-func (ddb *DoltDB) ResolveTagMeta(ctx context.Context, tagRef ref.TagRef) (*datas.TagMeta, error) {
+func (ddb *DoltDB) ResolveTagMeta(ctx context.Context, tagRef ref.TagRef) (*TagRefWithMeta, error) {
 	ds, err := ddb.db.GetDataset(ctx, tagRef.String())
 	if err != nil {
 		return nil, ErrTagNotFound
@@ -609,12 +621,13 @@ func (ddb *DoltDB) ResolveTagMeta(ctx context.Context, tagRef ref.TagRef) (*data
 		return nil, fmt.Errorf("tagRef head is not a tag")
 	}
 
-	meta, _, err := ds.HeadTag()
+	meta, commitAddr, err := ds.HeadTag()
 	if err != nil {
 		return nil, err
 	}
 
-	return meta, nil
+	addr, _ := ds.MaybeHeadAddr()
+	return &TagRefWithMeta{TagRef: tagRef, Meta: meta, CommitAddr: commitAddr, MaybeHeadAddr: addr}, nil
 }
 
 // ResolveWorkingSet takes a WorkingSetRef and returns the corresponding WorkingSet object.

go/libraries/doltcore/doltdb/tag.go

@@ -32,6 +32,31 @@ type Tag struct {
 	Commit *Commit
 }
 
+// NewTagFromTagRefWithMeta creates a new Tag object from a TagRefWithMeta.
+func NewTagFromTagRefWithMeta(ctx context.Context, name string, tagRefWithMeta *TagRefWithMeta, vrw types.ValueReadWriter, ns tree.NodeStore) (*Tag, error) {
+	dc, err := datas.LoadCommitAddr(ctx, vrw, tagRefWithMeta.CommitAddr)
+	if err != nil {
+		return nil, err
+	}
+
+	if dc.IsGhost() {
+		return nil, ErrGhostCommitEncountered
+	}
+
+	commit, err := NewCommit(ctx, vrw, ns, dc)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Tag{
+		Name:   name,
+		vrw:    vrw,
+		addr:   tagRefWithMeta.MaybeHeadAddr,
+		Meta:   tagRefWithMeta.Meta,
+		Commit: commit,
+	}, nil
+}
+
 // NewTag creates a new Tag object.
 func NewTag(ctx context.Context, name string, ds datas.Dataset, vrw types.ValueReadWriter, ns tree.NodeStore) (*Tag, error) {
 	meta, commitAddr, err := ds.HeadTag()

go/libraries/doltcore/env/actions/tag.go

@@ -139,11 +139,6 @@ func IterResolvedTags(ctx context.Context, ddb *doltdb.DoltDB, cb func(tag *dolt
 	return nil
 }
 
-type TagRefWithMeta struct {
-	TagRef ref.TagRef
-	Meta   *datas.TagMeta
-}
-
 const DefaultPageSize = 100
 
 // IterResolvedTagsPaginated iterates over tags in dEnv.DoltDB from newest to oldest, resolving the tag to a commit and calling cb().
@@ -155,17 +150,17 @@ func IterResolvedTagsPaginated(ctx context.Context, ddb *doltdb.DoltDB, startTag
 	}
 
 	// for each tag, get the meta
-	tagMetas := make([]*TagRefWithMeta, 0, len(tagRefs))
+	tagMetas := make([]*doltdb.TagRefWithMeta, 0, len(tagRefs))
 	for _, r := range tagRefs {
 		tr, ok := r.(ref.TagRef)
 		if !ok {
 			return "", fmt.Errorf("DoltDB.GetTags() returned non-tag DoltRef")
 		}
-		meta, err := ddb.ResolveTagMeta(ctx, tr)
+		tm, err := ddb.ResolveTagMeta(ctx, tr)
 		if err != nil {
 			return "", err
 		}
-		tagMetas = append(tagMetas, &TagRefWithMeta{TagRef: tr, Meta: meta})
+		tagMetas = append(tagMetas, tm)
 	}
 
 	// sort by meta timestamp
@@ -194,7 +189,7 @@ func IterResolvedTagsPaginated(ctx context.Context, ddb *doltdb.DoltDB, startTag
 
 	// resolve tags for this page
 	for _, tm := range pageTagMetas {
-		tag, err := ddb.ResolveTag(ctx, tm.TagRef)
+		tag, err := ddb.ResolveTagFromTagRefWithMeta(ctx, tm)
 		if err != nil {
 			return "", err
 		}

go/libraries/doltcore/env/actions/tag_test.go

@@ -68,7 +68,6 @@ func TestVisitResolvedTag(t *testing.T) {
 	})
 	require.Equal(t, doltdb.ErrTagNotFound, err)
 }
-
 func TestIterResolvedTagsPaginated(t *testing.T) {
 	dEnv, _ := createTestEnv()
 	ctx := context.Background()