RemoveEmptyValueCompactionFilter - A compaction filter which removes entries which have an empty value

src.mk

@@ -98,6 +98,7 @@ LIB_SOURCES =                                                   \
   utilities/backupable/backupable_db.cc                         \
   utilities/convenience/convenience.cc                          \
   utilities/checkpoint/checkpoint.cc                            \
+  utilities/compaction_filters/remove_emptyvalue_compactionfilter.cc    \
   utilities/document/document_db.cc                             \
   utilities/document/json_document_builder.cc                   \
   utilities/document/json_document.cc                           \

utilities/compaction_filters/remove_emptyvalue_compactionfilter.cc

@@ -0,0 +1,30 @@
+// Copyright (c) 2015, Facebook, Inc.  All rights reserved.
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+
+#ifndef ROCKSDB_LITE
+
+#include <string>
+
+#include "rocksdb/slice.h"
+#include "utilities/compaction_filters/remove_emptyvalue_compactionfilter.h"
+
+namespace rocksdb {
+
+const char* RemoveEmptyValueCompactionFilter::Name() const {
+  return "RemoveEmptyValueCompactionFilter";
+}
+
+bool RemoveEmptyValueCompactionFilter::Filter(int level,
+    const Slice& key,
+    const Slice& existing_value,
+    std::string* new_value,
+    bool* value_changed) const {
+
+  // remove kv pairs that have empty values
+  return existing_value.empty();
+}
+
+}  // namespace rocksdb
+#endif  // !ROCKSDB_LITE

utilities/compaction_filters/remove_emptyvalue_compactionfilter.h

@@ -0,0 +1,27 @@
+// Copyright (c) 2015, Facebook, Inc.  All rights reserved.
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+
+#ifndef ROCKSDB_LITE
+
+#pragma once
+
+#include <string>
+
+#include "rocksdb/compaction_filter.h"
+#include "rocksdb/slice.h"
+
+namespace rocksdb {
+
+class RemoveEmptyValueCompactionFilter : public CompactionFilter {
+ public:
+    const char* Name() const override;
+    bool Filter(int level,
+        const Slice& key,
+        const Slice& existing_value,
+        std::string* new_value,
+        bool* value_changed) const override;
+};
+}  // namespace rocksdb
+#endif  // !ROCKSDB_LITE