rocksdb/db/pre_release_callback.h

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// 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"
namespace rocksdb {
class DB;
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