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https://github.com/XRPLF/rippled.git
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4c696ed001
Summary: flush_on_destroy has a default value of false and the memtable is flushed in the dbimpl-destructor only when that is set to true. Because we want the memtable to be flushed everytime that the destructor is called(db is closed) and the cases where we work with the memtable only are very less it is a good idea to give this a default value of true. Thus the put from ldb wil have its data flushed to disk in the destructor and the next Get will be able to read it when opened with OpenForReadOnly. The reason that ldb could read the latest value when the db was opened in the normal Open mode is that the Get from normal Open first reads the memtable and directly finds the latest value written there and the Get from OpenForReadOnly doesn't have access to the memtable (which is correct because all its Put/Modify) are disabled Test Plan: make all; ldb put and get and scans Reviewers: dhruba, heyongqiang, sheki Reviewed By: heyongqiang CC: kosievdmerwe, zshao, dilipj, kailiu Differential Revision: https://reviews.facebook.net/D8631
93 lines
2.5 KiB
C++
93 lines
2.5 KiB
C++
// Copyright (c) 2012 Facebook. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#include "db/db_impl_readonly.h"
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#include "db/db_impl.h"
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#include <algorithm>
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#include <set>
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#include <string>
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#include <stdint.h>
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#include <stdio.h>
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#include <vector>
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#include <algorithm>
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#include "db/db_iter.h"
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#include "db/dbformat.h"
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#include "db/filename.h"
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#include "db/log_reader.h"
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#include "db/log_writer.h"
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#include "db/memtable.h"
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#include "db/table_cache.h"
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#include "db/version_set.h"
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#include "db/write_batch_internal.h"
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#include "leveldb/db.h"
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#include "leveldb/env.h"
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#include "leveldb/status.h"
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#include "leveldb/table.h"
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#include "leveldb/table_builder.h"
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#include "port/port.h"
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#include "table/block.h"
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#include "table/merger.h"
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#include "table/two_level_iterator.h"
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#include "util/coding.h"
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#include "util/logging.h"
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#include "util/build_version.h"
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namespace leveldb {
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DBImplReadOnly::DBImplReadOnly(const Options& options,
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const std::string& dbname)
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: DBImpl(options, dbname) {
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Log(options_.info_log, "Opening the db in read only mode");
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}
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DBImplReadOnly::~DBImplReadOnly() {
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}
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// Implementations of the DB interface
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Status DBImplReadOnly::Get(const ReadOptions& options,
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const Slice& key,
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std::string* value) {
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Status s;
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Version* current = versions_->current();
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SequenceNumber snapshot = versions_->LastSequence();
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LookupKey lkey(key, snapshot);
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Version::GetStats stats;
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s = current->Get(options, lkey, value, &stats);
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return s;
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}
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Iterator* DBImplReadOnly::NewIterator(const ReadOptions& options) {
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std::vector<Iterator*> list;
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versions_->current()->AddIterators(options, &list);
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Iterator* internal_iter =
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NewMergingIterator(&internal_comparator_, &list[0], list.size());
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return NewDBIterator(
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&dbname_, env_, user_comparator(), internal_iter,
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(options.snapshot != NULL
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? reinterpret_cast<const SnapshotImpl*>(options.snapshot)->number_
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: versions_->LastSequence()));
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}
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Status DB::OpenForReadOnly(const Options& options, const std::string& dbname,
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DB** dbptr, bool error_if_log_file_exist) {
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*dbptr = NULL;
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DBImplReadOnly* impl = new DBImplReadOnly(options, dbname);
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impl->mutex_.Lock();
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VersionEdit edit(impl->NumberLevels());
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Status s = impl->Recover(&edit, impl->GetMemTable(),
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error_if_log_file_exist);
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impl->mutex_.Unlock();
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if (s.ok()) {
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*dbptr = impl;
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} else {
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delete impl;
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}
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return s;
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}
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}
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