1 files changed, 51 insertions, 0 deletions
diff --git a/src/rocksdb/util/hash_containers.h b/src/rocksdb/util/hash_containers.h
new file mode 100644
index 000000000..52be3718c
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+++ b/src/rocksdb/util/hash_containers.h
@@ -0,0 +1,51 @@
+//  Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+// This header establishes compile-time pluggable implementations of hashed
+// container structures, so that deployments have the option of minimal
+// dependencies with ok performance (e.g. std::unordered_map) or more
+// dependencies with optimized performance (e.g. folly::F14FastMap).
+
+#pragma once
+
+#include "rocksdb/rocksdb_namespace.h"
+
+#ifdef USE_FOLLY
+
+#include <folly/container/F14Map.h>
+#include <folly/container/F14Set.h>
+
+namespace ROCKSDB_NAMESPACE {
+
+template <typename K, typename V>
+using UnorderedMap = folly::F14FastMap<K, V>;
+
+template <typename K, typename V, typename H>
+using UnorderedMapH = folly::F14FastMap<K, V, H>;
+
+template <typename K>
+using UnorderedSet = folly::F14FastSet<K>;
+
+}  // namespace ROCKSDB_NAMESPACE
+
+#else
+
+#include <unordered_map>
+#include <unordered_set>
+
+namespace ROCKSDB_NAMESPACE {
+
+template <typename K, typename V>
+using UnorderedMap = std::unordered_map<K, V>;
+
+template <typename K, typename V, typename H>
+using UnorderedMapH = std::unordered_map<K, V, H>;
+
+template <typename K>
+using UnorderedSet = std::unordered_set<K>;
+
+}  // namespace ROCKSDB_NAMESPACE
+
+#endif