From ef9754910e1b4c32c556d030c929bb4eebd0398d Mon Sep 17 00:00:00 2001
From: Xiang Li <xiangli.cs@gmail.com>
Date: Tue, 28 Jun 2016 08:49:44 -0700
Subject: [PATCH] mvcc: do not hash consistent index

---
 mvcc/backend/backend.go      | 16 ++++++++++++----
 mvcc/backend/backend_test.go |  4 ++--
 mvcc/kvstore.go              |  9 ++++++++-
 mvcc/kvstore_test.go         | 14 +++++++-------
 4 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/mvcc/backend/backend.go b/mvcc/backend/backend.go
index c9b41307b..51b89021d 100644
--- a/mvcc/backend/backend.go
+++ b/mvcc/backend/backend.go
@@ -55,7 +55,7 @@ const (
 type Backend interface {
 	BatchTx() BatchTx
 	Snapshot() Snapshot
-	Hash() (uint32, error)
+	Hash(ignores map[IgnoreKey]struct{}) (uint32, error)
 	// Size returns the current size of the backend.
 	Size() int64
 	Defrag() error
@@ -144,7 +144,12 @@ func (b *backend) Snapshot() Snapshot {
 	return &snapshot{tx}
 }
 
-func (b *backend) Hash() (uint32, error) {
+type IgnoreKey struct {
+	Bucket string
+	Key    string
+}
+
+func (b *backend) Hash(ignores map[IgnoreKey]struct{}) (uint32, error) {
 	h := crc32.New(crc32.MakeTable(crc32.Castagnoli))
 
 	b.mu.RLock()
@@ -158,8 +163,11 @@ func (b *backend) Hash() (uint32, error) {
 			}
 			h.Write(next)
 			b.ForEach(func(k, v []byte) error {
-				h.Write(k)
-				h.Write(v)
+				bk := IgnoreKey{Bucket: string(next), Key: string(k)}
+				if _, ok := ignores[bk]; !ok {
+					h.Write(k)
+					h.Write(v)
+				}
 				return nil
 			})
 		}
diff --git a/mvcc/backend/backend_test.go b/mvcc/backend/backend_test.go
index 769c95f2c..06d908db5 100644
--- a/mvcc/backend/backend_test.go
+++ b/mvcc/backend/backend_test.go
@@ -141,7 +141,7 @@ func TestBackendDefrag(t *testing.T) {
 	size := b.Size()
 
 	// shrink and check hash
-	oh, err := b.Hash()
+	oh, err := b.Hash(nil)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -151,7 +151,7 @@ func TestBackendDefrag(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	nh, err := b.Hash()
+	nh, err := b.Hash(nil)
 	if err != nil {
 		t.Fatal(err)
 	}
diff --git a/mvcc/kvstore.go b/mvcc/kvstore.go
index 6712910ed..b8d53324b 100644
--- a/mvcc/kvstore.go
+++ b/mvcc/kvstore.go
@@ -320,7 +320,14 @@ func (s *store) Hash() (uint32, int64, error) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 
-	h, err := s.b.Hash()
+	// ignore hash consistent index field for now.
+	// consistent index might be changed due to v2 internal sync, which
+	// is not controllable by the user.
+	ignores := make(map[backend.IgnoreKey]struct{})
+	bk := backend.IgnoreKey{Bucket: string(metaBucketName), Key: string(consistentIndexKeyName)}
+	ignores[bk] = struct{}{}
+
+	h, err := s.b.Hash(ignores)
 	rev := s.currentRev.main
 	return h, rev, err
 }
diff --git a/mvcc/kvstore_test.go b/mvcc/kvstore_test.go
index 814e989a2..c401354fe 100644
--- a/mvcc/kvstore_test.go
+++ b/mvcc/kvstore_test.go
@@ -593,13 +593,13 @@ type fakeBackend struct {
 	tx *fakeBatchTx
 }
 
-func (b *fakeBackend) BatchTx() backend.BatchTx   { return b.tx }
-func (b *fakeBackend) Hash() (uint32, error)      { return 0, nil }
-func (b *fakeBackend) Size() int64                { return 0 }
-func (b *fakeBackend) Snapshot() backend.Snapshot { return nil }
-func (b *fakeBackend) ForceCommit()               {}
-func (b *fakeBackend) Defrag() error              { return nil }
-func (b *fakeBackend) Close() error               { return nil }
+func (b *fakeBackend) BatchTx() backend.BatchTx                                    { return b.tx }
+func (b *fakeBackend) Hash(ignores map[backend.IgnoreKey]struct{}) (uint32, error) { return 0, nil }
+func (b *fakeBackend) Size() int64                                                 { return 0 }
+func (b *fakeBackend) Snapshot() backend.Snapshot                                  { return nil }
+func (b *fakeBackend) ForceCommit()                                                {}
+func (b *fakeBackend) Defrag() error                                               { return nil }
+func (b *fakeBackend) Close() error                                                { return nil }
 
 type indexGetResp struct {
 	rev     revision