blockstore: save only the last seen commit (#6212)

store/store.go

@@ -477,13 +477,18 @@ func (bs *BlockStore) SaveBlock(block *types.Block, blockParts *types.PartSet, s
 	}
 
 	// Save seen commit (seen +2/3 precommits for block)
-	// NOTE: we can delete this at a later height
 	pbsc := seenCommit.ToProto()
 	seenCommitBytes := mustEncode(pbsc)
 	if err := batch.Set(seenCommitKey(height), seenCommitBytes); err != nil {
 		panic(err)
 	}
 
+	// remove the previous seen commit that we have just replaced with the
+	// canonical commit
+	if err := batch.Delete(seenCommitKey(height - 1)); err != nil {
+		panic(err)
+	}
+
 	if err := batch.WriteSync(); err != nil {
 		panic(err)
 	}

store/store_test.go

@@ -35,8 +35,14 @@ func makeTestCommit(height int64, timestamp time.Time) *types.Commit {
 		Timestamp:        timestamp,
 		Signature:        []byte("Signature"),
 	}}
-	return types.NewCommit(height, 0,
-		types.BlockID{Hash: []byte(""), PartSetHeader: types.PartSetHeader{Hash: []byte(""), Total: 2}}, commitSigs)
+	return types.NewCommit(
+		height,
+		0,
+		types.BlockID{
+			Hash:          crypto.CRandBytes(32),
+			PartSetHeader: types.PartSetHeader{Hash: crypto.CRandBytes(32), Total: 2},
+		},
+		commitSigs)
 }
 
 func makeTxs(height int64) (txs []types.Tx) {
@@ -504,6 +510,45 @@ func TestBlockFetchAtHeight(t *testing.T) {
 	require.Nil(t, blockAtHeightPlus2, "expecting an unsuccessful load of Height()+2")
 }
 
+func TestSeenAndCanonicalCommit(t *testing.T) {
+	bs, _ := freshBlockStore()
+	height := int64(2)
+	loadCommit := func() (interface{}, error) {
+		meta := bs.LoadSeenCommit(height)
+		return meta, nil
+	}
+
+	// Initially no contents.
+	// 1. Requesting for a non-existent blockMeta shouldn't fail
+	res, _, panicErr := doFn(loadCommit)
+	require.Nil(t, panicErr, "a non-existent blockMeta shouldn't cause a panic")
+	require.Nil(t, res, "a non-existent blockMeta should return nil")
+
+	// produce a few blocks and check that the correct seen and cannoncial commits
+	// are persisted.
+	for h := int64(3); h <= 5; h++ {
+		c1 := bs.LoadSeenCommit(h)
+		require.Nil(t, c1)
+		c2 := bs.LoadBlockCommit(h - 1)
+		require.Nil(t, c2)
+		blockCommit := makeTestCommit(h-1, tmtime.Now())
+		block := makeBlock(h, state, blockCommit)
+		partSet := block.MakePartSet(2)
+		seenCommit := makeTestCommit(h, tmtime.Now())
+		bs.SaveBlock(block, partSet, seenCommit)
+		c3 := bs.LoadSeenCommit(h)
+		require.Equal(t, seenCommit.Hash(), c3.Hash())
+		// the previous seen commit should be removed
+		c4 := bs.LoadSeenCommit(h - 1)
+		require.Nil(t, c4)
+		c5 := bs.LoadBlockCommit(h)
+		require.Nil(t, c5)
+		c6 := bs.LoadBlockCommit(h - 1)
+		require.Equal(t, blockCommit.Hash(), c6.Hash())
+	}
+
+}
+
 func doFn(fn func() (interface{}, error)) (res interface{}, err error, panicErr error) {
 	defer func() {
 		if r := recover(); r != nil {