1 files changed, 37 insertions, 0 deletions
diff --git a/src/rocksdb/db/pre_release_callback.h b/src/rocksdb/db/pre_release_callback.h
new file mode 100644
index 000000000..6b9039487
--- /dev/null
+++ b/src/rocksdb/db/pre_release_callback.h
@@ -0,0 +1,37 @@
+// Copyright (c) 2011-present, Facebook, Inc.  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).
+
+#pragma once
+
+#include "rocksdb/status.h"
+#include "rocksdb/types.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+class PreReleaseCallback {
+ public:
+  virtual ~PreReleaseCallback() {}
+
+  // Will be called while on the write thread after the write to the WAL and
+  // before the write to memtable. This is useful if any operation needs to be
+  // done before the write gets visible to the readers, or if we want to reduce
+  // the overhead of locking by updating something sequentially while we are on
+  // the write thread. If the callback fails, this function returns a non-OK
+  // status, the sequence number will not be released, and same status will be
+  // propagated to all the writers in the write group.
+  // seq is the sequence number that is used for this write and will be
+  // released.
+  // is_mem_disabled is currently used for debugging purposes to assert that
+  // the callback is done from the right write queue.
+  // If non-zero, log_number indicates the WAL log to which we wrote.
+  // index >= 0 specifies the order of callback in the same write thread.
+  // total > index specifies the total number of callbacks in the same write
+  // thread. Together with index, could be used to reduce the redundant
+  // operations among the callbacks.
+  virtual Status Callback(SequenceNumber seq, bool is_mem_disabled,
+                          uint64_t log_number, size_t index, size_t total) = 0;
+};
+
+}  // namespace ROCKSDB_NAMESPACE