From d050f9c11095cdbdb29f8d039d6c3de447bf6fed Mon Sep 17 00:00:00 2001
From: Andy Arthur <andy@dolthub.com>
Date: Mon, 12 Oct 2020 18:12:07 -0700
Subject: [PATCH] pr feedback, added visited set to traversal

---
 bats/garbage_collection.bats           |  2 ++
 go/libraries/doltcore/doltdb/doltdb.go | 17 ++++-------------
 go/store/types/value_store.go          |  5 +++++
 3 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/bats/garbage_collection.bats b/bats/garbage_collection.bats
index 7fdedf3c46..9cb9e10988 100644
--- a/bats/garbage_collection.bats
+++ b/bats/garbage_collection.bats
@@ -128,5 +128,7 @@ SQL
     AFTER=$(du .dolt/noms/ | sed 's/[^0-9]*//g')
 
     # assert space was reclaimed
+    echo "$BEFORE"
+    echo "$AFTER"
     [ "$BEFORE" -gt "$AFTER" ]
 }
diff --git a/go/libraries/doltcore/doltdb/doltdb.go b/go/libraries/doltcore/doltdb/doltdb.go
index 2877ae85a2..c82796be93 100644
--- a/go/libraries/doltcore/doltdb/doltdb.go
+++ b/go/libraries/doltcore/doltdb/doltdb.go
@@ -18,6 +18,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"math/rand"
 	"strings"
 	"time"
 
@@ -25,7 +26,6 @@ import (
 	"github.com/dolthub/dolt/go/libraries/doltcore/ref"
 	"github.com/dolthub/dolt/go/libraries/utils/filesys"
 	"github.com/dolthub/dolt/go/libraries/utils/pantoerr"
-	"github.com/dolthub/dolt/go/libraries/utils/set"
 	"github.com/dolthub/dolt/go/store/chunks"
 	"github.com/dolthub/dolt/go/store/datas"
 	"github.com/dolthub/dolt/go/store/hash"
@@ -921,6 +921,7 @@ func (ddb *DoltDB) GC(ctx context.Context, uncommitedVals ...hash.Hash) error {
 		return err
 	}
 
+	rand.Seed(time.Now().UnixNano())
 	tmpDatasets := make([]datas.Dataset, len(uncommitedVals))
 	for i, h := range uncommitedVals {
 		v, err := ddb.db.ReadValue(ctx, h)
@@ -931,7 +932,7 @@ func (ddb *DoltDB) GC(ctx context.Context, uncommitedVals ...hash.Hash) error {
 			return fmt.Errorf("empty value for value hash %s", h.String())
 		}
 
-		ds, err := ddb.db.GetDataset(ctx, fmt.Sprintf("tmp/%d", time.Now().UnixNano()))
+		ds, err := ddb.db.GetDataset(ctx, fmt.Sprintf("tmp/%d", rand.Int63()))
 		if err != nil {
 			return err
 		}
@@ -972,16 +973,6 @@ func (ddb *DoltDB) GC(ctx context.Context, uncommitedVals ...hash.Hash) error {
 }
 
 func (ddb *DoltDB) pruneUnreferencedDatasets(ctx context.Context) error {
-	rr, err := ddb.GetRefs(ctx)
-	if err != nil {
-		return err
-	}
-
-	refs := set.NewStrSet(nil)
-	for _, r := range rr {
-		refs.Add(r.String())
-	}
-
 	dd, err := ddb.db.Datasets(ctx)
 	if err != nil {
 		return err
@@ -990,7 +981,7 @@ func (ddb *DoltDB) pruneUnreferencedDatasets(ctx context.Context) error {
 	var deletes []string
 	_ = dd.Iter(ctx, func(ds, _ types.Value) (stop bool, err error) {
 		dsID := string(ds.(types.String))
-		if !refs.Contains(dsID) {
+		if !ref.IsRef(dsID) {
 			deletes = append(deletes, dsID)
 		}
 		return false, nil
diff --git a/go/store/types/value_store.go b/go/store/types/value_store.go
index 4dfe09ca69..80d6fcae66 100644
--- a/go/store/types/value_store.go
+++ b/go/store/types/value_store.go
@@ -599,6 +599,7 @@ func (lvs *ValueStore) GC(ctx context.Context) error {
 			return err
 		}
 		hashQueue := list.New()
+		visited := hash.NewHashSet(root)
 		hashQueue.PushBack(root)
 		for hashQueue.Len() > 0 {
 			e := hashQueue.Front()
@@ -615,11 +616,15 @@ func (lvs *ValueStore) GC(ctx context.Context) error {
 
 			err = val.WalkRefs(lvs.nbf, func(reachable Ref) error {
 				h := reachable.TargetHash()
+				if visited.Has(h) {
+					return nil
+				}
 				err := sendHash(h)
 				if err != nil {
 					return err
 				}
 				hashQueue.PushBack(h)
+				visited.Insert(h)
 				return nil
 			})
 			if err != nil {