diff --git a/include/leveldb/db.h b/include/leveldb/db.h
index cb74cda..81303b8 100644
--- a/include/leveldb/db.h
+++ b/include/leveldb/db.h
@@ -7,6 +7,7 @@
 
 #include <cstdint>
 #include <cstdio>
+#include <vector>
 
 #include "leveldb/export.h"
 #include "leveldb/iterator.h"
@@ -14,6 +15,9 @@
 
 namespace leveldb {
 
+using Field = std::pair<std::string, std::string>;
+using FieldArray = std::vector<std::pair<std::string, std::string>>;
+
 // Update CMakeLists.txt if you change these
 static const int kMajorVersion = 1;
 static const int kMinorVersion = 23;
@@ -87,6 +91,14 @@ class LEVELDB_EXPORT DB {
   virtual Status Get(const ReadOptions& options, const Slice& key,
                      std::string* value) = 0;
 
+  virtual Status Put_fields(const WriteOptions& options, const Slice& key,
+                     const FieldArray& fields) = 0;
+
+  virtual Status Get_fields(const ReadOptions& options, const Slice& key,
+                     FieldArray* fields) = 0;
+
+  virtual std::vector<std::string> FindKeysByField(leveldb::DB* db, Field &field) = 0;
+
   // Return a heap-allocated iterator over the contents of the database.
   // The result of NewIterator() is initially invalid (caller must
   // call one of the Seek methods on the iterator before using it).