1 // Copyright (c) 2011-present, Facebook, Inc. All rights reserved. 2 // This source code is licensed under both the GPLv2 (found in the 3 // COPYING file in the root directory) and Apache 2.0 License 4 // (found in the LICENSE.Apache file in the root directory). 5 6 #pragma once 7 8 #include "rocksdb/status.h" 9 10 namespace ROCKSDB_NAMESPACE { 11 12 class DB; 13 14 class PreReleaseCallback { 15 public: ~PreReleaseCallback()16 virtual ~PreReleaseCallback() {} 17 18 // Will be called while on the write thread after the write to the WAL and 19 // before the write to memtable. This is useful if any operation needs to be 20 // done before the write gets visible to the readers, or if we want to reduce 21 // the overhead of locking by updating something sequentially while we are on 22 // the write thread. If the callback fails, this function returns a non-OK 23 // status, the sequence number will not be released, and same status will be 24 // propagated to all the writers in the write group. 25 // seq is the sequence number that is used for this write and will be 26 // released. 27 // is_mem_disabled is currently used for debugging purposes to assert that 28 // the callback is done from the right write queue. 29 // If non-zero, log_number indicates the WAL log to which we wrote. 30 // index >= 0 specifies the order of callback in the same write thread. 31 // total > index specifies the total number of callbacks in the same write 32 // thread. Together with index, could be used to reduce the redundant 33 // operations among the callbacks. 34 virtual Status Callback(SequenceNumber seq, bool is_mem_disabled, 35 uint64_t log_number, size_t index, size_t total) = 0; 36 }; 37 38 } // namespace ROCKSDB_NAMESPACE 39