Merge pull request #3720 from Yawning/boltdb-fixes

Fix fundemental BoltDB backend correctness issues.

CHANGELOG_PENDING.md

@@ -28,3 +28,5 @@
 * [rpc] [\#3686](https://github.com/tendermint/tendermint/pull/3686) `HTTPClient#Call` returns wrapped errors, so a caller could use `errors.Cause` to retrieve an error code.
 
 ### BUG FIXES:
+- [libs/db] Fixed the BoltDB backend's Batch.Delete implementation (@Yawning)
+- [libs/db] Fixed the BoltDB backend's Get and Iterator implementation (@Yawning)

libs/db/boltdb.go

@@ -66,7 +66,9 @@ func (bdb *BoltDB) Get(key []byte) (value []byte) {
 	key = nonEmptyKey(nonNilBytes(key))
 	err := bdb.db.View(func(tx *bbolt.Tx) error {
 		b := tx.Bucket(bucket)
-		value = b.Get(key)
+		if v := b.Get(key); v != nil {
+			value = append([]byte{}, v...)
+		}
 		return nil
 	})
 	if err != nil {
@@ -149,20 +151,14 @@ func (bdb *BoltDB) Stats() map[string]string {
 // boltDBBatch stores key values in sync.Map and dumps them to the underlying
 // DB upon Write call.
 type boltDBBatch struct {
-	buffer []struct {
-		k []byte
-		v []byte
-	}
 	db  *BoltDB
+	ops []operation
 }
 
 // NewBatch returns a new batch.
 func (bdb *BoltDB) NewBatch() Batch {
 	return &boltDBBatch{
-		buffer: make([]struct {
-			k []byte
-			v []byte
-		}, 0),
+		ops: nil,
 		db:  bdb,
 	}
 }
@@ -170,35 +166,31 @@ func (bdb *BoltDB) NewBatch() Batch {
 // It is safe to modify the contents of the argument after Set returns but not
 // before.
 func (bdb *boltDBBatch) Set(key, value []byte) {
-	bdb.buffer = append(bdb.buffer, struct {
-		k []byte
-		v []byte
-	}{
-		key, value,
-	})
+	bdb.ops = append(bdb.ops, operation{opTypeSet, key, value})
 }
 
 // It is safe to modify the contents of the argument after Delete returns but
 // not before.
 func (bdb *boltDBBatch) Delete(key []byte) {
-	for i, elem := range bdb.buffer {
-		if bytes.Equal(elem.k, key) {
-			// delete without preserving order
-			bdb.buffer[i] = bdb.buffer[len(bdb.buffer)-1]
-			bdb.buffer = bdb.buffer[:len(bdb.buffer)-1]
-			return
-		}
-	}
+	bdb.ops = append(bdb.ops, operation{opTypeDelete, key, nil})
 }
 
 // NOTE: the operation is synchronous (see BoltDB for reasons)
 func (bdb *boltDBBatch) Write() {
 	err := bdb.db.db.Batch(func(tx *bbolt.Tx) error {
 		b := tx.Bucket(bucket)
-		for _, elem := range bdb.buffer {
-			if putErr := b.Put(elem.k, elem.v); putErr != nil {
+		for _, op := range bdb.ops {
+			key := nonEmptyKey(nonNilBytes(op.key))
+			switch op.opType {
+			case opTypeSet:
+				if putErr := b.Put(key, op.value); putErr != nil {
 					return putErr
 				}
+			case opTypeDelete:
+				if delErr := b.Delete(key); delErr != nil {
+					return delErr
+				}
+			}
 		}
 		return nil
 	})
@@ -322,12 +314,16 @@ func (itr *boltDBIterator) Next() {
 
 func (itr *boltDBIterator) Key() []byte {
 	itr.assertIsValid()
-	return itr.currentKey
+	return append([]byte{}, itr.currentKey...)
 }
 
 func (itr *boltDBIterator) Value() []byte {
 	itr.assertIsValid()
-	return itr.currentValue
+	var value []byte
+	if itr.currentValue != nil {
+		value = append([]byte{}, itr.currentValue...)
+	}
+	return value
 }
 
 func (itr *boltDBIterator) Close() {