rocksdb/db/internal_stats.h
Siying Dong d59549298f Skip deleted WALs during recovery
Summary:
This patch record min log number to keep to the manifest while flushing SST files to ignore them and any WAL older than them during recovery. This is to avoid scenarios when we have a gap between the WAL files are fed to the recovery procedure. The gap could happen by for example out-of-order WAL deletion. Such gap could cause problems in 2PC recovery where the prepared and commit entry are placed into two separate WAL and gap in the WALs could result into not processing the WAL with the commit entry and hence breaking the 2PC recovery logic.

Before the commit, for 2PC case, we determined which log number to keep in FindObsoleteFiles(). We looked at the earliest logs with outstanding prepare entries, or prepare entries whose respective commit or abort are in memtable. With the commit, the same calculation is done while we apply the SST flush. Just before installing the flush file, we precompute the earliest log file to keep after the flush finishes using the same logic (but skipping the memtables just flushed), record this information to the manifest entry for this new flushed SST file. This pre-computed value is also remembered in memory, and will later be used to determine whether a log file can be deleted. This value is unlikely to change until next flush because the commit entry will stay in memtable. (In WritePrepared, we could have removed the older log files as soon as all prepared entries are committed. It's not yet done anyway. Even if we do it, the only thing we loss with this new approach is earlier log deletion between two flushes, which does not guarantee to happen anyway because the obsolete file clean-up function is only executed after flush or compaction)

This min log number to keep is stored in the manifest using the safely-ignore customized field of AddFile entry, in order to guarantee that the DB generated using newer release can be opened by previous releases no older than 4.2.
Closes https://github.com/facebook/rocksdb/pull/3765

Differential Revision: D7747618

Pulled By: siying

fbshipit-source-id: d00c92105b4f83852e9754a1b70d6b64cb590729
2018-05-03 15:43:09 -07:00

654 lines
23 KiB
C++

// 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).
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
//
#pragma once
#include <map>
#include <string>
#include <vector>
#include "db/version_set.h"
class ColumnFamilyData;
namespace rocksdb {
class DBImpl;
class MemTableList;
// Config for retrieving a property's value.
struct DBPropertyInfo {
bool need_out_of_mutex;
// gcc had an internal error for initializing union of pointer-to-member-
// functions. Workaround is to populate exactly one of the following function
// pointers with a non-nullptr value.
// @param value Value-result argument for storing the property's string value
// @param suffix Argument portion of the property. For example, suffix would
// be "5" for the property "rocksdb.num-files-at-level5". So far, only
// certain string properties take an argument.
bool (InternalStats::*handle_string)(std::string* value, Slice suffix);
// @param value Value-result argument for storing the property's uint64 value
// @param db Many of the int properties rely on DBImpl methods.
// @param version Version is needed in case the property is retrieved without
// holding db mutex, which is only supported for int properties.
bool (InternalStats::*handle_int)(uint64_t* value, DBImpl* db,
Version* version);
// @param props Map of general properties to populate
bool (InternalStats::*handle_map)(std::map<std::string, std::string>* props);
};
extern const DBPropertyInfo* GetPropertyInfo(const Slice& property);
#ifndef ROCKSDB_LITE
#undef SCORE
enum class LevelStatType {
INVALID = 0,
NUM_FILES,
COMPACTED_FILES,
SIZE_BYTES,
SCORE,
READ_GB,
RN_GB,
RNP1_GB,
WRITE_GB,
W_NEW_GB,
MOVED_GB,
WRITE_AMP,
READ_MBPS,
WRITE_MBPS,
COMP_SEC,
COMP_COUNT,
AVG_SEC,
KEY_IN,
KEY_DROP,
TOTAL // total number of types
};
struct LevelStat {
// This what will be L?.property_name in the flat map returned to the user
std::string property_name;
// This will be what we will print in the header in the cli
std::string header_name;
};
class InternalStats {
public:
static const std::map<LevelStatType, LevelStat> compaction_level_stats;
enum InternalCFStatsType {
L0_FILE_COUNT_LIMIT_SLOWDOWNS,
LOCKED_L0_FILE_COUNT_LIMIT_SLOWDOWNS,
MEMTABLE_LIMIT_STOPS,
MEMTABLE_LIMIT_SLOWDOWNS,
L0_FILE_COUNT_LIMIT_STOPS,
LOCKED_L0_FILE_COUNT_LIMIT_STOPS,
PENDING_COMPACTION_BYTES_LIMIT_SLOWDOWNS,
PENDING_COMPACTION_BYTES_LIMIT_STOPS,
WRITE_STALLS_ENUM_MAX,
BYTES_FLUSHED,
BYTES_INGESTED_ADD_FILE,
INGESTED_NUM_FILES_TOTAL,
INGESTED_LEVEL0_NUM_FILES_TOTAL,
INGESTED_NUM_KEYS_TOTAL,
INTERNAL_CF_STATS_ENUM_MAX,
};
enum InternalDBStatsType {
WAL_FILE_BYTES,
WAL_FILE_SYNCED,
BYTES_WRITTEN,
NUMBER_KEYS_WRITTEN,
WRITE_DONE_BY_OTHER,
WRITE_DONE_BY_SELF,
WRITE_WITH_WAL,
WRITE_STALL_MICROS,
INTERNAL_DB_STATS_ENUM_MAX,
};
InternalStats(int num_levels, Env* env, ColumnFamilyData* cfd)
: db_stats_{},
cf_stats_value_{},
cf_stats_count_{},
comp_stats_(num_levels),
file_read_latency_(num_levels),
bg_error_count_(0),
number_levels_(num_levels),
env_(env),
cfd_(cfd),
started_at_(env->NowMicros()) {}
// Per level compaction stats. comp_stats_[level] stores the stats for
// compactions that produced data for the specified "level".
struct CompactionStats {
uint64_t micros;
// The number of bytes read from all non-output levels
uint64_t bytes_read_non_output_levels;
// The number of bytes read from the compaction output level.
uint64_t bytes_read_output_level;
// Total number of bytes written during compaction
uint64_t bytes_written;
// Total number of bytes moved to the output level
uint64_t bytes_moved;
// The number of compaction input files in all non-output levels.
int num_input_files_in_non_output_levels;
// The number of compaction input files in the output level.
int num_input_files_in_output_level;
// The number of compaction output files.
int num_output_files;
// Total incoming entries during compaction between levels N and N+1
uint64_t num_input_records;
// Accumulated diff number of entries
// (num input entries - num output entires) for compaction levels N and N+1
uint64_t num_dropped_records;
// Number of compactions done
int count;
// Number of compactions done per CompactionReason
int counts[static_cast<int>(CompactionReason::kNumOfReasons)];
explicit CompactionStats()
: micros(0),
bytes_read_non_output_levels(0),
bytes_read_output_level(0),
bytes_written(0),
bytes_moved(0),
num_input_files_in_non_output_levels(0),
num_input_files_in_output_level(0),
num_output_files(0),
num_input_records(0),
num_dropped_records(0),
count(0) {
int num_of_reasons = static_cast<int>(CompactionReason::kNumOfReasons);
for (int i = 0; i < num_of_reasons; i++) {
counts[i] = 0;
}
}
explicit CompactionStats(CompactionReason reason, int c)
: micros(0),
bytes_read_non_output_levels(0),
bytes_read_output_level(0),
bytes_written(0),
bytes_moved(0),
num_input_files_in_non_output_levels(0),
num_input_files_in_output_level(0),
num_output_files(0),
num_input_records(0),
num_dropped_records(0),
count(c) {
int num_of_reasons = static_cast<int>(CompactionReason::kNumOfReasons);
for (int i = 0; i < num_of_reasons; i++) {
counts[i] = 0;
}
int r = static_cast<int>(reason);
if (r >= 0 && r < num_of_reasons) {
counts[r] = c;
} else {
count = 0;
}
}
explicit CompactionStats(const CompactionStats& c)
: micros(c.micros),
bytes_read_non_output_levels(c.bytes_read_non_output_levels),
bytes_read_output_level(c.bytes_read_output_level),
bytes_written(c.bytes_written),
bytes_moved(c.bytes_moved),
num_input_files_in_non_output_levels(
c.num_input_files_in_non_output_levels),
num_input_files_in_output_level(
c.num_input_files_in_output_level),
num_output_files(c.num_output_files),
num_input_records(c.num_input_records),
num_dropped_records(c.num_dropped_records),
count(c.count) {
int num_of_reasons = static_cast<int>(CompactionReason::kNumOfReasons);
for (int i = 0; i < num_of_reasons; i++) {
counts[i] = c.counts[i];
}
}
void Clear() {
this->micros = 0;
this->bytes_read_non_output_levels = 0;
this->bytes_read_output_level = 0;
this->bytes_written = 0;
this->bytes_moved = 0;
this->num_input_files_in_non_output_levels = 0;
this->num_input_files_in_output_level = 0;
this->num_output_files = 0;
this->num_input_records = 0;
this->num_dropped_records = 0;
this->count = 0;
int num_of_reasons = static_cast<int>(CompactionReason::kNumOfReasons);
for (int i = 0; i < num_of_reasons; i++) {
counts[i] = 0;
}
}
void Add(const CompactionStats& c) {
this->micros += c.micros;
this->bytes_read_non_output_levels += c.bytes_read_non_output_levels;
this->bytes_read_output_level += c.bytes_read_output_level;
this->bytes_written += c.bytes_written;
this->bytes_moved += c.bytes_moved;
this->num_input_files_in_non_output_levels +=
c.num_input_files_in_non_output_levels;
this->num_input_files_in_output_level +=
c.num_input_files_in_output_level;
this->num_output_files += c.num_output_files;
this->num_input_records += c.num_input_records;
this->num_dropped_records += c.num_dropped_records;
this->count += c.count;
int num_of_reasons = static_cast<int>(CompactionReason::kNumOfReasons);
for (int i = 0; i< num_of_reasons; i++) {
counts[i] += c.counts[i];
}
}
void Subtract(const CompactionStats& c) {
this->micros -= c.micros;
this->bytes_read_non_output_levels -= c.bytes_read_non_output_levels;
this->bytes_read_output_level -= c.bytes_read_output_level;
this->bytes_written -= c.bytes_written;
this->bytes_moved -= c.bytes_moved;
this->num_input_files_in_non_output_levels -=
c.num_input_files_in_non_output_levels;
this->num_input_files_in_output_level -=
c.num_input_files_in_output_level;
this->num_output_files -= c.num_output_files;
this->num_input_records -= c.num_input_records;
this->num_dropped_records -= c.num_dropped_records;
this->count -= c.count;
int num_of_reasons = static_cast<int>(CompactionReason::kNumOfReasons);
for (int i = 0; i < num_of_reasons; i++) {
counts[i] -= c.counts[i];
}
}
};
void Clear() {
for (int i = 0; i < INTERNAL_DB_STATS_ENUM_MAX; i++) {
db_stats_[i].store(0);
}
for (int i = 0; i < INTERNAL_CF_STATS_ENUM_MAX; i++) {
cf_stats_count_[i] = 0;
cf_stats_value_[i] = 0;
}
for (auto& comp_stat : comp_stats_) {
comp_stat.Clear();
}
for (auto& h : file_read_latency_) {
h.Clear();
}
cf_stats_snapshot_.Clear();
db_stats_snapshot_.Clear();
bg_error_count_ = 0;
started_at_ = env_->NowMicros();
}
void AddCompactionStats(int level, const CompactionStats& stats) {
comp_stats_[level].Add(stats);
}
void IncBytesMoved(int level, uint64_t amount) {
comp_stats_[level].bytes_moved += amount;
}
void AddCFStats(InternalCFStatsType type, uint64_t value) {
cf_stats_value_[type] += value;
++cf_stats_count_[type];
}
void AddDBStats(InternalDBStatsType type, uint64_t value,
bool concurrent = false) {
auto& v = db_stats_[type];
if (concurrent) {
v.fetch_add(value, std::memory_order_relaxed);
} else {
v.store(v.load(std::memory_order_relaxed) + value,
std::memory_order_relaxed);
}
}
uint64_t GetDBStats(InternalDBStatsType type) {
return db_stats_[type].load(std::memory_order_relaxed);
}
HistogramImpl* GetFileReadHist(int level) {
return &file_read_latency_[level];
}
uint64_t GetBackgroundErrorCount() const { return bg_error_count_; }
uint64_t BumpAndGetBackgroundErrorCount() { return ++bg_error_count_; }
bool GetStringProperty(const DBPropertyInfo& property_info,
const Slice& property, std::string* value);
bool GetMapProperty(const DBPropertyInfo& property_info,
const Slice& property,
std::map<std::string, std::string>* value);
bool GetIntProperty(const DBPropertyInfo& property_info, uint64_t* value,
DBImpl* db);
bool GetIntPropertyOutOfMutex(const DBPropertyInfo& property_info,
Version* version, uint64_t* value);
const std::vector<CompactionStats>& TEST_GetCompactionStats() const {
return comp_stats_;
}
// Store a mapping from the user-facing DB::Properties string to our
// DBPropertyInfo struct used internally for retrieving properties.
static const std::unordered_map<std::string, DBPropertyInfo> ppt_name_to_info;
private:
void DumpDBStats(std::string* value);
void DumpCFMapStats(std::map<std::string, std::string>* cf_stats);
void DumpCFMapStats(
std::map<int, std::map<LevelStatType, double>>* level_stats,
CompactionStats* compaction_stats_sum);
void DumpCFMapStatsIOStalls(std::map<std::string, std::string>* cf_stats);
void DumpCFStats(std::string* value);
void DumpCFStatsNoFileHistogram(std::string* value);
void DumpCFFileHistogram(std::string* value);
bool HandleBlockCacheStat(Cache** block_cache);
// Per-DB stats
std::atomic<uint64_t> db_stats_[INTERNAL_DB_STATS_ENUM_MAX];
// Per-ColumnFamily stats
uint64_t cf_stats_value_[INTERNAL_CF_STATS_ENUM_MAX];
uint64_t cf_stats_count_[INTERNAL_CF_STATS_ENUM_MAX];
// Per-ColumnFamily/level compaction stats
std::vector<CompactionStats> comp_stats_;
std::vector<HistogramImpl> file_read_latency_;
// Used to compute per-interval statistics
struct CFStatsSnapshot {
// ColumnFamily-level stats
CompactionStats comp_stats;
uint64_t ingest_bytes_flush; // Bytes written to L0 (Flush)
uint64_t stall_count; // Stall count
// Stats from compaction jobs - bytes written, bytes read, duration.
uint64_t compact_bytes_write;
uint64_t compact_bytes_read;
uint64_t compact_micros;
double seconds_up;
// AddFile specific stats
uint64_t ingest_bytes_addfile; // Total Bytes ingested
uint64_t ingest_files_addfile; // Total number of files ingested
uint64_t ingest_l0_files_addfile; // Total number of files ingested to L0
uint64_t ingest_keys_addfile; // Total number of keys ingested
CFStatsSnapshot()
: ingest_bytes_flush(0),
stall_count(0),
compact_bytes_write(0),
compact_bytes_read(0),
compact_micros(0),
seconds_up(0),
ingest_bytes_addfile(0),
ingest_files_addfile(0),
ingest_l0_files_addfile(0),
ingest_keys_addfile(0) {}
void Clear() {
comp_stats.Clear();
ingest_bytes_flush = 0;
stall_count = 0;
compact_bytes_write = 0;
compact_bytes_read = 0;
compact_micros = 0;
seconds_up = 0;
ingest_bytes_addfile = 0;
ingest_files_addfile = 0;
ingest_l0_files_addfile = 0;
ingest_keys_addfile = 0;
}
} cf_stats_snapshot_;
struct DBStatsSnapshot {
// DB-level stats
uint64_t ingest_bytes; // Bytes written by user
uint64_t wal_bytes; // Bytes written to WAL
uint64_t wal_synced; // Number of times WAL is synced
uint64_t write_with_wal; // Number of writes that request WAL
// These count the number of writes processed by the calling thread or
// another thread.
uint64_t write_other;
uint64_t write_self;
// Total number of keys written. write_self and write_other measure number
// of write requests written, Each of the write request can contain updates
// to multiple keys. num_keys_written is total number of keys updated by all
// those writes.
uint64_t num_keys_written;
// Total time writes delayed by stalls.
uint64_t write_stall_micros;
double seconds_up;
DBStatsSnapshot()
: ingest_bytes(0),
wal_bytes(0),
wal_synced(0),
write_with_wal(0),
write_other(0),
write_self(0),
num_keys_written(0),
write_stall_micros(0),
seconds_up(0) {}
void Clear() {
ingest_bytes = 0;
wal_bytes = 0;
wal_synced = 0;
write_with_wal = 0;
write_other = 0;
write_self = 0;
num_keys_written = 0;
write_stall_micros = 0;
seconds_up = 0;
}
} db_stats_snapshot_;
// Handler functions for getting property values. They use "value" as a value-
// result argument, and return true upon successfully setting "value".
bool HandleNumFilesAtLevel(std::string* value, Slice suffix);
bool HandleCompressionRatioAtLevelPrefix(std::string* value, Slice suffix);
bool HandleLevelStats(std::string* value, Slice suffix);
bool HandleStats(std::string* value, Slice suffix);
bool HandleCFMapStats(std::map<std::string, std::string>* compaction_stats);
bool HandleCFStats(std::string* value, Slice suffix);
bool HandleCFStatsNoFileHistogram(std::string* value, Slice suffix);
bool HandleCFFileHistogram(std::string* value, Slice suffix);
bool HandleDBStats(std::string* value, Slice suffix);
bool HandleSsTables(std::string* value, Slice suffix);
bool HandleAggregatedTableProperties(std::string* value, Slice suffix);
bool HandleAggregatedTablePropertiesAtLevel(std::string* value, Slice suffix);
bool HandleNumImmutableMemTable(uint64_t* value, DBImpl* db,
Version* version);
bool HandleNumImmutableMemTableFlushed(uint64_t* value, DBImpl* db,
Version* version);
bool HandleMemTableFlushPending(uint64_t* value, DBImpl* db,
Version* version);
bool HandleNumRunningFlushes(uint64_t* value, DBImpl* db, Version* version);
bool HandleCompactionPending(uint64_t* value, DBImpl* db, Version* version);
bool HandleNumRunningCompactions(uint64_t* value, DBImpl* db,
Version* version);
bool HandleBackgroundErrors(uint64_t* value, DBImpl* db, Version* version);
bool HandleCurSizeActiveMemTable(uint64_t* value, DBImpl* db,
Version* version);
bool HandleCurSizeAllMemTables(uint64_t* value, DBImpl* db, Version* version);
bool HandleSizeAllMemTables(uint64_t* value, DBImpl* db, Version* version);
bool HandleNumEntriesActiveMemTable(uint64_t* value, DBImpl* db,
Version* version);
bool HandleNumEntriesImmMemTables(uint64_t* value, DBImpl* db,
Version* version);
bool HandleNumDeletesActiveMemTable(uint64_t* value, DBImpl* db,
Version* version);
bool HandleNumDeletesImmMemTables(uint64_t* value, DBImpl* db,
Version* version);
bool HandleEstimateNumKeys(uint64_t* value, DBImpl* db, Version* version);
bool HandleNumSnapshots(uint64_t* value, DBImpl* db, Version* version);
bool HandleOldestSnapshotTime(uint64_t* value, DBImpl* db, Version* version);
bool HandleNumLiveVersions(uint64_t* value, DBImpl* db, Version* version);
bool HandleCurrentSuperVersionNumber(uint64_t* value, DBImpl* db,
Version* version);
bool HandleIsFileDeletionsEnabled(uint64_t* value, DBImpl* db,
Version* version);
bool HandleBaseLevel(uint64_t* value, DBImpl* db, Version* version);
bool HandleTotalSstFilesSize(uint64_t* value, DBImpl* db, Version* version);
bool HandleLiveSstFilesSize(uint64_t* value, DBImpl* db, Version* version);
bool HandleEstimatePendingCompactionBytes(uint64_t* value, DBImpl* db,
Version* version);
bool HandleEstimateTableReadersMem(uint64_t* value, DBImpl* db,
Version* version);
bool HandleEstimateLiveDataSize(uint64_t* value, DBImpl* db,
Version* version);
bool HandleMinLogNumberToKeep(uint64_t* value, DBImpl* db, Version* version);
bool HandleActualDelayedWriteRate(uint64_t* value, DBImpl* db,
Version* version);
bool HandleIsWriteStopped(uint64_t* value, DBImpl* db, Version* version);
bool HandleEstimateOldestKeyTime(uint64_t* value, DBImpl* db,
Version* version);
bool HandleBlockCacheCapacity(uint64_t* value, DBImpl* db, Version* version);
bool HandleBlockCacheUsage(uint64_t* value, DBImpl* db, Version* version);
bool HandleBlockCachePinnedUsage(uint64_t* value, DBImpl* db,
Version* version);
// Total number of background errors encountered. Every time a flush task
// or compaction task fails, this counter is incremented. The failure can
// be caused by any possible reason, including file system errors, out of
// resources, or input file corruption. Failing when retrying the same flush
// or compaction will cause the counter to increase too.
uint64_t bg_error_count_;
const int number_levels_;
Env* env_;
ColumnFamilyData* cfd_;
uint64_t started_at_;
};
#else
class InternalStats {
public:
enum InternalCFStatsType {
L0_FILE_COUNT_LIMIT_SLOWDOWNS,
LOCKED_L0_FILE_COUNT_LIMIT_SLOWDOWNS,
MEMTABLE_LIMIT_STOPS,
MEMTABLE_LIMIT_SLOWDOWNS,
L0_FILE_COUNT_LIMIT_STOPS,
LOCKED_L0_FILE_COUNT_LIMIT_STOPS,
PENDING_COMPACTION_BYTES_LIMIT_SLOWDOWNS,
PENDING_COMPACTION_BYTES_LIMIT_STOPS,
WRITE_STALLS_ENUM_MAX,
BYTES_FLUSHED,
BYTES_INGESTED_ADD_FILE,
INGESTED_NUM_FILES_TOTAL,
INGESTED_LEVEL0_NUM_FILES_TOTAL,
INGESTED_NUM_KEYS_TOTAL,
INTERNAL_CF_STATS_ENUM_MAX,
};
enum InternalDBStatsType {
WAL_FILE_BYTES,
WAL_FILE_SYNCED,
BYTES_WRITTEN,
NUMBER_KEYS_WRITTEN,
WRITE_DONE_BY_OTHER,
WRITE_DONE_BY_SELF,
WRITE_WITH_WAL,
WRITE_STALL_MICROS,
INTERNAL_DB_STATS_ENUM_MAX,
};
InternalStats(int /*num_levels*/, Env* /*env*/, ColumnFamilyData* /*cfd*/) {}
struct CompactionStats {
uint64_t micros;
uint64_t bytes_read_non_output_levels;
uint64_t bytes_read_output_level;
uint64_t bytes_written;
uint64_t bytes_moved;
int num_input_files_in_non_output_levels;
int num_input_files_in_output_level;
int num_output_files;
uint64_t num_input_records;
uint64_t num_dropped_records;
int count;
explicit CompactionStats() {}
explicit CompactionStats(CompactionReason /*reason*/, int /*c*/) {}
explicit CompactionStats(const CompactionStats& /*c*/) {}
void Add(const CompactionStats& /*c*/) {}
void Subtract(const CompactionStats& /*c*/) {}
};
void AddCompactionStats(int /*level*/, const CompactionStats& /*stats*/) {}
void IncBytesMoved(int /*level*/, uint64_t /*amount*/) {}
void AddCFStats(InternalCFStatsType /*type*/, uint64_t /*value*/) {}
void AddDBStats(InternalDBStatsType /*type*/, uint64_t /*value*/,
bool /*concurrent */ = false) {}
HistogramImpl* GetFileReadHist(int /*level*/) { return nullptr; }
uint64_t GetBackgroundErrorCount() const { return 0; }
uint64_t BumpAndGetBackgroundErrorCount() { return 0; }
bool GetStringProperty(const DBPropertyInfo& /*property_info*/,
const Slice& /*property*/, std::string* /*value*/) {
return false;
}
bool GetMapProperty(const DBPropertyInfo& /*property_info*/,
const Slice& /*property*/,
std::map<std::string, std::string>* /*value*/) {
return false;
}
bool GetIntProperty(const DBPropertyInfo& /*property_info*/, uint64_t* /*value*/,
DBImpl* /*db*/) const {
return false;
}
bool GetIntPropertyOutOfMutex(const DBPropertyInfo& /*property_info*/,
Version* /*version*/, uint64_t* /*value*/) const {
return false;
}
};
#endif // !ROCKSDB_LITE
} // namespace rocksdb