rocksdb/db/db_impl_readonly.cc
Siying Dong ef2211a9ca [RocksDB Performance Branch] Introduce MergeContext to Lazily Initialize merge operand list
Summary: In get operations, merge_operands is only used in few cases. Lazily initialize it can reduce average latency in some cases

Test Plan: make all check

Reviewers: haobo, kailiu, dhruba

Reviewed By: haobo

CC: igor, nkg-, leveldb

Differential Revision: https://reviews.facebook.net/D14415
2013-12-06 10:28:59 -08:00

102 lines
2.9 KiB
C++

// Copyright (c) 2013, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
// Copyright (c) 2012 Facebook. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "db/db_impl_readonly.h"
#include "db/db_impl.h"
#include <algorithm>
#include <set>
#include <string>
#include <stdint.h>
#include <stdio.h>
#include <vector>
#include <algorithm>
#include "db/db_iter.h"
#include "db/dbformat.h"
#include "db/filename.h"
#include "db/log_reader.h"
#include "db/log_writer.h"
#include "db/memtable.h"
#include "db/merge_context.h"
#include "db/table_cache.h"
#include "db/version_set.h"
#include "db/write_batch_internal.h"
#include "rocksdb/db.h"
#include "rocksdb/env.h"
#include "rocksdb/status.h"
#include "rocksdb/table.h"
#include "rocksdb/merge_operator.h"
#include "port/port.h"
#include "table/block.h"
#include "table/merger.h"
#include "table/two_level_iterator.h"
#include "util/coding.h"
#include "util/logging.h"
#include "util/build_version.h"
namespace rocksdb {
DBImplReadOnly::DBImplReadOnly(const Options& options,
const std::string& dbname)
: DBImpl(options, dbname) {
Log(options_.info_log, "Opening the db in read only mode");
}
DBImplReadOnly::~DBImplReadOnly() {
}
// Implementations of the DB interface
Status DBImplReadOnly::Get(const ReadOptions& options,
const Slice& key,
std::string* value) {
Status s;
MemTable* mem = GetMemTable();
Version* current = versions_->current();
SequenceNumber snapshot = versions_->LastSequence();
MergeContext merge_context;
LookupKey lkey(key, snapshot);
if (mem->Get(lkey, value, &s, merge_context, options_)) {
} else {
Version::GetStats stats;
current->Get(options, lkey, value, &s, &merge_context, &stats, options_);
}
return s;
}
Iterator* DBImplReadOnly::NewIterator(const ReadOptions& options) {
SequenceNumber latest_snapshot;
Iterator* internal_iter = NewInternalIterator(options, &latest_snapshot);
return NewDBIterator(
&dbname_, env_, options_, user_comparator(),internal_iter,
(options.snapshot != nullptr
? reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_
: latest_snapshot));
}
Status DB::OpenForReadOnly(const Options& options, const std::string& dbname,
DB** dbptr, bool error_if_log_file_exist) {
*dbptr = nullptr;
DBImplReadOnly* impl = new DBImplReadOnly(options, dbname);
impl->mutex_.Lock();
VersionEdit edit(impl->NumberLevels());
Status s = impl->Recover(&edit, impl->GetMemTable(),
error_if_log_file_exist);
impl->mutex_.Unlock();
if (s.ok()) {
*dbptr = impl;
} else {
delete impl;
}
return s;
}
}