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387 lignes
12 KiB
387 lignes
12 KiB
// Copyright (c) 2011 The LevelDB Authors. 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. See the AUTHORS file for names of contributors.
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//
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// We recover the contents of the descriptor from the other files we find.
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// (1) Any log files are first converted to tables
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// (2) We scan every table to compute
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// (a) smallest/largest for the table
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// (b) largest sequence number in the table
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// (3) We generate descriptor contents:
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// - log number is set to zero
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// - next-file-number is set to 1 + largest file number we found
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// - last-sequence-number is set to largest sequence# found across
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// all tables (see 2c)
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// - compaction pointers are cleared
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// - every table file is added at level 0
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//
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// Possible optimization 1:
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// (a) Compute total size and use to pick appropriate max-level M
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// (b) Sort tables by largest sequence# in the table
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// (c) For each table: if it overlaps earlier table, place in level-0,
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// else place in level-M.
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// Possible optimization 2:
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// Store per-table metadata (smallest, largest, largest-seq#, ...)
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// in the table's meta section to speed up ScanTable.
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#include "db/builder.h"
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#include "db/db_impl.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_edit.h"
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#include "db/write_batch_internal.h"
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#include "leveldb/comparator.h"
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#include "leveldb/db.h"
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#include "leveldb/env.h"
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namespace leveldb {
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namespace {
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class Repairer {
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public:
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Repairer(const std::string& dbname, const Options& options)
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: dbname_(dbname),
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env_(options.env),
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icmp_(options.comparator),
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options_(SanitizeOptions(dbname, &icmp_, options)),
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owns_info_log_(options_.info_log != options.info_log),
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owns_cache_(options_.block_cache != options.block_cache),
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next_file_number_(1) {
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// TableCache can be small since we expect each table to be opened once.
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table_cache_ = new TableCache(dbname_, &options_, 10);
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}
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~Repairer() {
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delete table_cache_;
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if (owns_info_log_) {
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delete options_.info_log;
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}
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if (owns_cache_) {
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delete options_.block_cache;
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}
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}
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Status Run() {
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Status status = FindFiles();
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if (status.ok()) {
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ConvertLogFilesToTables();
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ExtractMetaData();
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status = WriteDescriptor();
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}
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if (status.ok()) {
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unsigned long long bytes = 0;
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for (size_t i = 0; i < tables_.size(); i++) {
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bytes += tables_[i].meta.file_size;
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}
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Log(options_.info_log,
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"**** Repaired leveldb %s; "
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"recovered %d files; %llu bytes. "
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"Some data may have been lost. "
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"****",
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dbname_.c_str(),
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static_cast<int>(tables_.size()),
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bytes);
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}
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return status;
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}
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private:
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struct TableInfo {
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FileMetaData meta;
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SequenceNumber max_sequence;
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};
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std::string const dbname_;
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Env* const env_;
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InternalKeyComparator const icmp_;
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Options const options_;
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bool owns_info_log_;
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bool owns_cache_;
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TableCache* table_cache_;
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VersionEdit edit_;
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std::vector<std::string> manifests_;
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std::vector<uint64_t> table_numbers_;
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std::vector<uint64_t> logs_;
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std::vector<TableInfo> tables_;
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uint64_t next_file_number_;
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Status FindFiles() {
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std::vector<std::string> filenames;
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Status status = env_->GetChildren(dbname_, &filenames);
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if (!status.ok()) {
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return status;
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}
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if (filenames.empty()) {
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return Status::IOError(dbname_, "repair found no files");
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}
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uint64_t number;
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FileType type;
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for (size_t i = 0; i < filenames.size(); i++) {
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if (ParseFileName(filenames[i], &number, &type)) {
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if (type == kDescriptorFile) {
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manifests_.push_back(filenames[i]);
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} else {
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if (number + 1 > next_file_number_) {
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next_file_number_ = number + 1;
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}
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if (type == kLogFile) {
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logs_.push_back(number);
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} else if (type == kTableFile) {
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table_numbers_.push_back(number);
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} else {
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// Ignore other files
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}
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}
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}
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}
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return status;
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}
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void ConvertLogFilesToTables() {
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for (size_t i = 0; i < logs_.size(); i++) {
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std::string logname = LogFileName(dbname_, logs_[i]);
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Status status = ConvertLogToTable(logs_[i]);
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if (!status.ok()) {
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Log(options_.info_log, "Log #%llu: ignoring conversion error: %s",
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(unsigned long long) logs_[i],
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status.ToString().c_str());
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}
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ArchiveFile(logname);
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}
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}
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Status ConvertLogToTable(uint64_t log) {
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struct LogReporter : public log::Reader::Reporter {
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Env* env;
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Logger* info_log;
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uint64_t lognum;
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virtual void Corruption(size_t bytes, const Status& s) {
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// We print error messages for corruption, but continue repairing.
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Log(info_log, "Log #%llu: dropping %d bytes; %s",
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(unsigned long long) lognum,
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static_cast<int>(bytes),
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s.ToString().c_str());
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}
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};
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// Open the log file
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std::string logname = LogFileName(dbname_, log);
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SequentialFile* lfile;
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Status status = env_->NewSequentialFile(logname, &lfile);
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if (!status.ok()) {
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return status;
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}
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// Create the log reader.
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LogReporter reporter;
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reporter.env = env_;
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reporter.info_log = options_.info_log;
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reporter.lognum = log;
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// We intentially make log::Reader do checksumming so that
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// corruptions cause entire commits to be skipped instead of
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// propagating bad information (like overly large sequence
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// numbers).
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log::Reader reader(lfile, &reporter, false/*do not checksum*/,
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0/*initial_offset*/);
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// Read all the records and add to a memtable
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std::string scratch;
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Slice record;
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WriteBatch batch;
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MemTable* mem = new MemTable(icmp_);
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mem->Ref();
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int counter = 0;
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while (reader.ReadRecord(&record, &scratch)) {
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if (record.size() < 12) {
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reporter.Corruption(
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record.size(), Status::Corruption("log record too small"));
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continue;
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}
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WriteBatchInternal::SetContents(&batch, record);
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status = WriteBatchInternal::InsertInto(&batch, mem);
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if (status.ok()) {
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counter += WriteBatchInternal::Count(&batch);
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} else {
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Log(options_.info_log, "Log #%llu: ignoring %s",
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(unsigned long long) log,
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status.ToString().c_str());
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status = Status::OK(); // Keep going with rest of file
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}
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}
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delete lfile;
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// Do not record a version edit for this conversion to a Table
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// since ExtractMetaData() will also generate edits.
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FileMetaData meta;
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meta.number = next_file_number_++;
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Iterator* iter = mem->NewIterator();
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status = BuildTable(dbname_, env_, options_, table_cache_, iter, &meta);
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delete iter;
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mem->Unref();
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mem = NULL;
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if (status.ok()) {
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if (meta.file_size > 0) {
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table_numbers_.push_back(meta.number);
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}
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}
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Log(options_.info_log, "Log #%llu: %d ops saved to Table #%llu %s",
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(unsigned long long) log,
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counter,
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(unsigned long long) meta.number,
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status.ToString().c_str());
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return status;
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}
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void ExtractMetaData() {
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std::vector<TableInfo> kept;
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for (size_t i = 0; i < table_numbers_.size(); i++) {
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TableInfo t;
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t.meta.number = table_numbers_[i];
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Status status = ScanTable(&t);
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if (!status.ok()) {
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std::string fname = TableFileName(dbname_, table_numbers_[i]);
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Log(options_.info_log, "Table #%llu: ignoring %s",
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(unsigned long long) table_numbers_[i],
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status.ToString().c_str());
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ArchiveFile(fname);
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} else {
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tables_.push_back(t);
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}
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}
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}
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Status ScanTable(TableInfo* t) {
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std::string fname = TableFileName(dbname_, t->meta.number);
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int counter = 0;
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Status status = env_->GetFileSize(fname, &t->meta.file_size);
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if (status.ok()) {
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Iterator* iter = table_cache_->NewIterator(
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ReadOptions(), t->meta.number, t->meta.file_size);
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bool empty = true;
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ParsedInternalKey parsed;
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t->max_sequence = 0;
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for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
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Slice key = iter->key();
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if (!ParseInternalKey(key, &parsed)) {
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Log(options_.info_log, "Table #%llu: unparsable key %s",
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(unsigned long long) t->meta.number,
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EscapeString(key).c_str());
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continue;
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}
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counter++;
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if (empty) {
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empty = false;
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t->meta.smallest.DecodeFrom(key);
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}
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t->meta.largest.DecodeFrom(key);
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if (parsed.sequence > t->max_sequence) {
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t->max_sequence = parsed.sequence;
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}
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}
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if (!iter->status().ok()) {
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status = iter->status();
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}
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delete iter;
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}
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Log(options_.info_log, "Table #%llu: %d entries %s",
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(unsigned long long) t->meta.number,
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counter,
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status.ToString().c_str());
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return status;
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}
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Status WriteDescriptor() {
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std::string tmp = TempFileName(dbname_, 1);
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WritableFile* file;
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Status status = env_->NewWritableFile(tmp, &file);
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if (!status.ok()) {
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return status;
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}
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SequenceNumber max_sequence = 0;
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for (size_t i = 0; i < tables_.size(); i++) {
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if (max_sequence < tables_[i].max_sequence) {
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max_sequence = tables_[i].max_sequence;
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}
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}
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edit_.SetComparatorName(icmp_.user_comparator()->Name());
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edit_.SetLogNumber(0);
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edit_.SetNextFile(next_file_number_);
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edit_.SetLastSequence(max_sequence);
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for (size_t i = 0; i < tables_.size(); i++) {
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// TODO(opt): separate out into multiple levels
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const TableInfo& t = tables_[i];
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edit_.AddFile(0, t.meta.number, t.meta.file_size,
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t.meta.smallest, t.meta.largest);
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}
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//fprintf(stderr, "NewDescriptor:\n%s\n", edit_.DebugString().c_str());
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{
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log::Writer log(file);
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std::string record;
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edit_.EncodeTo(&record);
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status = log.AddRecord(record);
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}
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if (status.ok()) {
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status = file->Close();
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}
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delete file;
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file = NULL;
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if (!status.ok()) {
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env_->DeleteFile(tmp);
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} else {
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// Discard older manifests
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for (size_t i = 0; i < manifests_.size(); i++) {
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ArchiveFile(dbname_ + "/" + manifests_[i]);
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}
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// Install new manifest
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status = env_->RenameFile(tmp, DescriptorFileName(dbname_, 1));
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if (status.ok()) {
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status = SetCurrentFile(env_, dbname_, 1);
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} else {
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env_->DeleteFile(tmp);
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}
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}
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return status;
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}
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void ArchiveFile(const std::string& fname) {
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// Move into another directory. E.g., for
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// dir/foo
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// rename to
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// dir/lost/foo
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const char* slash = strrchr(fname.c_str(), '/');
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std::string new_dir;
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if (slash != NULL) {
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new_dir.assign(fname.data(), slash - fname.data());
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}
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new_dir.append("/lost");
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env_->CreateDir(new_dir); // Ignore error
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std::string new_file = new_dir;
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new_file.append("/");
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new_file.append((slash == NULL) ? fname.c_str() : slash + 1);
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Status s = env_->RenameFile(fname, new_file);
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Log(options_.info_log, "Archiving %s: %s\n",
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fname.c_str(), s.ToString().c_str());
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}
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};
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}
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Status RepairDB(const std::string& dbname, const Options& options) {
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Repairer repairer(dbname, options);
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return repairer.Run();
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}
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}
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