leveldb/util/options.cc
Sanjay Ghemawat 251ebf5dc7 LevelDB now attempts to reuse the preceding MANIFEST and log file when re-opened.
(Based on a suggestion by cmumford.)

"open" benchmark on my workstation speeds up significantly since we
can now avoid three fdatasync calls and a compaction per open:

  Before: ~80000 microseconds
  After:    ~130 microseconds

Details:

(1) Added Options::reuse_logs (currently defaults to false) to control
new behavior.  The intention is to change the default to true after some
baking.

(2) Added Env::NewAppendableFile() whose default implementation returns
a not-supported error.

(3) VersionSet::Recovery attempts to reuse the MANIFEST from which
it is recovering.

(4) DBImpl recovery attempts to reuse the last log file and memtable.

(5) db_test.cc now tests a new configuration that sets reuse_logs to true.

(6) fault_injection_test also tests a reuse_logs==true config.

(7) Added a new recovery_test.
2014-12-11 08:13:18 -08:00

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// 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.
#include "leveldb/options.h"
#include "leveldb/comparator.h"
#include "leveldb/env.h"
namespace leveldb {
Options::Options()
: comparator(BytewiseComparator()),
create_if_missing(false),
error_if_exists(false),
paranoid_checks(false),
env(Env::Default()),
info_log(NULL),
write_buffer_size(4<<20),
max_open_files(1000),
block_cache(NULL),
block_size(4096),
block_restart_interval(16),
compression(kSnappyCompression),
reuse_logs(false),
filter_policy(NULL) {
}
} // namespace leveldb