1 files changed, 17 insertions, 8 deletions
diff --git a/include/leveldb/write_batch.h b/include/leveldb/write_batch.h
index b6d72cb..94d4115 100644
--- a/include/leveldb/write_batch.h
+++ b/include/leveldb/write_batch.h
@@ -22,6 +22,7 @@
 #define STORAGE_LEVELDB_INCLUDE_WRITE_BATCH_H_
 
 #include <string>
+
 #include "leveldb/export.h"
 #include "leveldb/status.h"
 
@@ -31,11 +32,18 @@ class Slice;
 
 class LEVELDB_EXPORT WriteBatch {
  public:
+  class LEVELDB_EXPORT Handler {
+   public:
+    virtual ~Handler();
+    virtual void Put(const Slice& key, const Slice& value) = 0;
+    virtual void Delete(const Slice& key) = 0;
+  };
+
   WriteBatch();
 
   // Intentionally copyable.
   WriteBatch(const WriteBatch&) = default;
-  WriteBatch& operator =(const WriteBatch&) = default;
+  WriteBatch& operator=(const WriteBatch&) = default;
 
   ~WriteBatch();
 
@@ -52,15 +60,16 @@ class LEVELDB_EXPORT WriteBatch {
   //
   // This number is tied to implementation details, and may change across
   // releases. It is intended for LevelDB usage metrics.
-  size_t ApproximateSize();
+  size_t ApproximateSize() const;
+
+  // Copies the operations in "source" to this batch.
+  //
+  // This runs in O(source size) time. However, the constant factor is better
+  // than calling Iterate() over the source batch with a Handler that replicates
+  // the operations into this batch.
+  void Append(const WriteBatch& source);
 
   // Support for iterating over the contents of a batch.
-  class Handler {
-   public:
-    virtual ~Handler();
-    virtual void Put(const Slice& key, const Slice& value) = 0;
-    virtual void Delete(const Slice& key) = 0;
-  };
   Status Iterate(Handler* handler) const;
 
  private: