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leveldb/db/db_impl.cc
jorlow@chromium.org 4671a695fc Move include files into a leveldb subdir. 
git-svn-id: https://leveldb.googlecode.com/svn/trunk@18 62dab493-f737-651d-591e-8d6aee1b9529
2011-03-30 18:35:40 +00:00

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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 "db/db_impl.h"
#include <algorithm>
#include <set>
#include <string>
#include <stdint.h>
#include <stdio.h>
#include <vector>
#include "db/builder.h"
#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/table_cache.h"
#include "db/version_set.h"
#include "db/write_batch_internal.h"
#include "leveldb/db.h"
#include "leveldb/env.h"
#include "leveldb/status.h"
#include "leveldb/table.h"
#include "leveldb/table_builder.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/mutexlock.h"
namespace leveldb {
struct DBImpl::CompactionState {
Compaction* const compaction;
// Sequence numbers < smallest_snapshot are not significant since we
// will never have to service a snapshot below smallest_snapshot.
// Therefore if we have seen a sequence number S <= smallest_snapshot,
// we can drop all entries for the same key with sequence numbers < S.
SequenceNumber smallest_snapshot;
// Files produced by compaction
struct Output {
uint64_t number;
uint64_t file_size;
InternalKey smallest, largest;
};
std::vector<Output> outputs;
// State kept for output being generated
WritableFile* outfile;
TableBuilder* builder;
uint64_t total_bytes;
Output* current_output() { return &outputs[outputs.size()-1]; }
explicit CompactionState(Compaction* c)
: compaction(c),
outfile(NULL),
builder(NULL),
total_bytes(0) {
}
};
namespace {
class NullWritableFile : public WritableFile {
public:
virtual Status Append(const Slice& data) { return Status::OK(); }
virtual Status Close() { return Status::OK(); }
virtual Status Flush() { return Status::OK(); }
virtual Status Sync() { return Status::OK(); }
};
}
// Fix user-supplied options to be reasonable
template <class T,class V>
static void ClipToRange(T* ptr, V minvalue, V maxvalue) {
if (*ptr > maxvalue) *ptr = maxvalue;
if (*ptr < minvalue) *ptr = minvalue;
}
Options SanitizeOptions(const std::string& dbname,
const InternalKeyComparator* icmp,
const Options& src) {
Options result = src;
result.comparator = icmp;
ClipToRange(&result.max_open_files, 20, 50000);
ClipToRange(&result.write_buffer_size, 64<<10, 1<<30);
ClipToRange(&result.large_value_threshold, 16<<10, 1<<30);
ClipToRange(&result.block_size, 1<<10, 4<<20);
if (result.info_log == NULL) {
// Open a log file in the same directory as the db
src.env->CreateDir(dbname); // In case it does not exist
src.env->RenameFile(InfoLogFileName(dbname), OldInfoLogFileName(dbname));
Status s = src.env->NewWritableFile(InfoLogFileName(dbname),
&result.info_log);
if (!s.ok()) {
// No place suitable for logging
result.info_log = new NullWritableFile;
}
}
return result;
}
DBImpl::DBImpl(const Options& options, const std::string& dbname)
: env_(options.env),
internal_comparator_(options.comparator),
options_(SanitizeOptions(dbname, &internal_comparator_, options)),
owns_info_log_(options_.info_log != options.info_log),
dbname_(dbname),
db_lock_(NULL),
shutting_down_(NULL),
bg_cv_(&mutex_),
compacting_cv_(&mutex_),
last_sequence_(0),
mem_(new MemTable(internal_comparator_)),
logfile_(NULL),
log_(NULL),
log_number_(0),
bg_compaction_scheduled_(false),
compacting_(false) {
// Reserve ten files or so for other uses and give the rest to TableCache.
const int table_cache_size = options.max_open_files - 10;
table_cache_ = new TableCache(dbname_, &options_, table_cache_size);
versions_ = new VersionSet(dbname_, &options_, table_cache_,
&internal_comparator_);
}
DBImpl::~DBImpl() {
// Wait for background work to finish
mutex_.Lock();
shutting_down_.Release_Store(this); // Any non-NULL value is ok
if (bg_compaction_scheduled_) {
while (bg_compaction_scheduled_) {
bg_cv_.Wait();
}
}
mutex_.Unlock();
if (db_lock_ != NULL) {
env_->UnlockFile(db_lock_);
}
delete versions_;
delete mem_;
delete log_;
delete logfile_;
delete table_cache_;
if (owns_info_log_) {
delete options_.info_log;
}
}
Status DBImpl::NewDB() {
assert(log_number_ == 0);
assert(last_sequence_ == 0);
VersionEdit new_db;
new_db.SetComparatorName(user_comparator()->Name());
new_db.SetLogNumber(log_number_);
new_db.SetNextFile(2);
new_db.SetLastSequence(0);
const std::string manifest = DescriptorFileName(dbname_, 1);
WritableFile* file;
Status s = env_->NewWritableFile(manifest, &file);
if (!s.ok()) {
return s;
}
{
log::Writer log(file);
std::string record;
new_db.EncodeTo(&record);
s = log.AddRecord(record);
if (s.ok()) {
s = file->Close();
}
}
delete file;
if (s.ok()) {
// Make "CURRENT" file that points to the new manifest file.
s = SetCurrentFile(env_, dbname_, 1);
} else {
env_->DeleteFile(manifest);
}
return s;
}
Status DBImpl::Install(VersionEdit* edit,
uint64_t new_log_number,
MemTable* cleanup_mem) {
mutex_.AssertHeld();
edit->SetLogNumber(new_log_number);
edit->SetLastSequence(last_sequence_);
return versions_->LogAndApply(edit, cleanup_mem);
}
void DBImpl::MaybeIgnoreError(Status* s) const {
if (s->ok() || options_.paranoid_checks) {
// No change needed
} else {
Log(env_, options_.info_log, "Ignoring error %s", s->ToString().c_str());
*s = Status::OK();
}
}
void DBImpl::DeleteObsoleteFiles() {
// Make a set of all of the live files
std::set<uint64_t> live = pending_outputs_;
versions_->AddLiveFiles(&live);
versions_->CleanupLargeValueRefs(live, log_number_);
std::vector<std::string> filenames;
env_->GetChildren(dbname_, &filenames); // Ignoring errors on purpose
uint64_t number;
LargeValueRef large_ref;
FileType type;
for (int i = 0; i < filenames.size(); i++) {
if (ParseFileName(filenames[i], &number, &large_ref, &type)) {
bool keep = true;
switch (type) {
case kLogFile:
keep = (number == log_number_);
break;
case kDescriptorFile:
// Keep my manifest file, and any newer incarnations'
// (in case there is a race that allows other incarnations)
keep = (number >= versions_->ManifestFileNumber());
break;
case kTableFile:
keep = (live.find(number) != live.end());
break;
case kTempFile:
// Any temp files that are currently being written to must
// be recorded in pending_outputs_, which is inserted into "live"
keep = (live.find(number) != live.end());
break;
case kLargeValueFile:
keep = versions_->LargeValueIsLive(large_ref);
break;
case kCurrentFile:
case kDBLockFile:
case kInfoLogFile:
keep = true;
break;
}
if (!keep) {
if (type == kTableFile) {
table_cache_->Evict(number);
}
Log(env_, options_.info_log, "Delete type=%d #%lld\n",
int(type),
static_cast<unsigned long long>(number));
env_->DeleteFile(dbname_ + "/" + filenames[i]);
}
}
}
}
Status DBImpl::Recover(VersionEdit* edit) {
mutex_.AssertHeld();
// Ignore error from CreateDir since the creation of the DB is
// committed only when the descriptor is created, and this directory
// may already exist from a previous failed creation attempt.
env_->CreateDir(dbname_);
assert(db_lock_ == NULL);
Status s = env_->LockFile(LockFileName(dbname_), &db_lock_);
if (!s.ok()) {
return s;
}
if (!env_->FileExists(CurrentFileName(dbname_))) {
if (options_.create_if_missing) {
s = NewDB();
if (!s.ok()) {
return s;
}
} else {
return Status::InvalidArgument(
dbname_, "does not exist (create_if_missing is false)");
}
} else {
if (options_.error_if_exists) {
return Status::InvalidArgument(
dbname_, "exists (error_if_exists is true)");
}
}
s = versions_->Recover(&log_number_, &last_sequence_);
if (s.ok()) {
// Recover from the log file named in the descriptor
SequenceNumber max_sequence(0);
if (log_number_ != 0) { // log_number_ == 0 indicates initial empty state
s = RecoverLogFile(log_number_, edit, &max_sequence);
}
if (s.ok()) {
last_sequence_ =
last_sequence_ > max_sequence ? last_sequence_ : max_sequence;
}
}
return s;
}
Status DBImpl::RecoverLogFile(uint64_t log_number,
VersionEdit* edit,
SequenceNumber* max_sequence) {
struct LogReporter : public log::Reader::Reporter {
Env* env;
WritableFile* info_log;
const char* fname;
Status* status; // NULL if options_.paranoid_checks==false
virtual void Corruption(size_t bytes, const Status& s) {
Log(env, info_log, "%s%s: dropping %d bytes; %s",
(this->status == NULL ? "(ignoring error) " : ""),
fname, static_cast<int>(bytes), s.ToString().c_str());
if (this->status != NULL && this->status->ok()) *this->status = s;
}
};
mutex_.AssertHeld();
// Open the log file
std::string fname = LogFileName(dbname_, log_number);
SequentialFile* file;
Status status = env_->NewSequentialFile(fname, &file);
if (!status.ok()) {
MaybeIgnoreError(&status);
return status;
}
// Create the log reader.
LogReporter reporter;
reporter.env = env_;
reporter.info_log = options_.info_log;
reporter.fname = fname.c_str();
reporter.status = (options_.paranoid_checks ? &status : NULL);
// We intentially make log::Reader do checksumming even if
// paranoid_checks==false so that corruptions cause entire commits
// to be skipped instead of propagating bad information (like overly
// large sequence numbers).
log::Reader reader(file, &reporter, true/*checksum*/);
Log(env_, options_.info_log, "Recovering log #%llu",
(unsigned long long) log_number);
// Read all the records and add to a memtable
std::string scratch;
Slice record;
WriteBatch batch;
MemTable* mem = NULL;
while (reader.ReadRecord(&record, &scratch) &&
status.ok()) {
if (record.size() < 12) {
reporter.Corruption(
record.size(), Status::Corruption("log record too small"));
continue;
}
WriteBatchInternal::SetContents(&batch, record);
if (mem == NULL) {
mem = new MemTable(internal_comparator_);
}
status = WriteBatchInternal::InsertInto(&batch, mem);
MaybeIgnoreError(&status);
if (!status.ok()) {
break;
}
const SequenceNumber last_seq =
WriteBatchInternal::Sequence(&batch) +
WriteBatchInternal::Count(&batch) - 1;
if (last_seq > *max_sequence) {
*max_sequence = last_seq;
}
if (mem->ApproximateMemoryUsage() > options_.write_buffer_size) {
status = WriteLevel0Table(mem, edit);
if (!status.ok()) {
// Reflect errors immediately so that conditions like full
// file-systems cause the DB::Open() to fail.
break;
}
delete mem;
mem = NULL;
}
}
if (status.ok() && mem != NULL) {
status = WriteLevel0Table(mem, edit);
// Reflect errors immediately so that conditions like full
// file-systems cause the DB::Open() to fail.
}
delete mem;
delete file;
return status;
}
Status DBImpl::WriteLevel0Table(MemTable* mem, VersionEdit* edit) {
mutex_.AssertHeld();
FileMetaData meta;
meta.number = versions_->NewFileNumber();
pending_outputs_.insert(meta.number);
Iterator* iter = mem->NewIterator();
Log(env_, options_.info_log, "Level-0 table #%llu: started",
(unsigned long long) meta.number);
Status s = BuildTable(dbname_, env_, options_, table_cache_,
iter, &meta, edit);
Log(env_, options_.info_log, "Level-0 table #%llu: %lld bytes %s",
(unsigned long long) meta.number,
(unsigned long long) meta.file_size,
s.ToString().c_str());
delete iter;
pending_outputs_.erase(meta.number);
return s;
}
Status DBImpl::CompactMemTable() {
mutex_.AssertHeld();
WritableFile* lfile = NULL;
uint64_t new_log_number = versions_->NewFileNumber();
VersionEdit edit;
// Save the contents of the memtable as a new Table
Status s = WriteLevel0Table(mem_, &edit);
if (s.ok()) {
s = env_->NewWritableFile(LogFileName(dbname_, new_log_number), &lfile);
}
// Save a new descriptor with the new table and log number.
if (s.ok()) {
s = Install(&edit, new_log_number, mem_);
}
if (s.ok()) {
// Commit to the new state
mem_ = new MemTable(internal_comparator_);
delete log_;
delete logfile_;
logfile_ = lfile;
log_ = new log::Writer(lfile);
log_number_ = new_log_number;
DeleteObsoleteFiles();
MaybeScheduleCompaction();
} else {
delete lfile;
env_->DeleteFile(LogFileName(dbname_, new_log_number));
}
return s;
}
void DBImpl::TEST_CompactRange(
int level,
const std::string& begin,
const std::string& end) {
MutexLock l(&mutex_);
while (compacting_) {
compacting_cv_.Wait();
}
Compaction* c = versions_->CompactRange(
level,
InternalKey(begin, kMaxSequenceNumber, kValueTypeForSeek),
InternalKey(end, 0, static_cast<ValueType>(0)));
if (c != NULL) {
CompactionState* compact = new CompactionState(c);
DoCompactionWork(compact); // Ignore error in test compaction
CleanupCompaction(compact);
}
// Start any background compaction that may have been delayed by this thread
MaybeScheduleCompaction();
}
Status DBImpl::TEST_CompactMemTable() {
MutexLock l(&mutex_);
return CompactMemTable();
}
void DBImpl::MaybeScheduleCompaction() {
mutex_.AssertHeld();
if (bg_compaction_scheduled_) {
// Already scheduled
} else if (compacting_) {
// Some other thread is running a compaction. Do not conflict with it.
} else if (shutting_down_.Acquire_Load()) {
// DB is being deleted; no more background compactions
} else if (!versions_->NeedsCompaction()) {
// No work to be done
} else {
bg_compaction_scheduled_ = true;
env_->Schedule(&DBImpl::BGWork, this);
}
}
void DBImpl::BGWork(void* db) {
reinterpret_cast<DBImpl*>(db)->BackgroundCall();
}
void DBImpl::BackgroundCall() {
MutexLock l(&mutex_);
assert(bg_compaction_scheduled_);
if (!shutting_down_.Acquire_Load() &&
!compacting_) {
BackgroundCompaction();
}
bg_compaction_scheduled_ = false;
bg_cv_.SignalAll();
// Previous compaction may have produced too many files in a level,
// so reschedule another compaction if needed.
MaybeScheduleCompaction();
}
void DBImpl::BackgroundCompaction() {
mutex_.AssertHeld();
Compaction* c = versions_->PickCompaction();
if (c == NULL) {
// Nothing to do
return;
}
Status status;
if (c->IsTrivialMove()) {
// Move file to next level
assert(c->num_input_files(0) == 1);
FileMetaData* f = c->input(0, 0);
c->edit()->DeleteFile(c->level(), f->number);
c->edit()->AddFile(c->level() + 1, f->number, f->file_size,
f->smallest, f->largest);
status = Install(c->edit(), log_number_, NULL);
Log(env_, options_.info_log, "Moved #%lld to level-%d %lld bytes %s\n",
static_cast<unsigned long long>(f->number),
c->level() + 1,
static_cast<unsigned long long>(f->file_size),
status.ToString().c_str());
} else {
CompactionState* compact = new CompactionState(c);
status = DoCompactionWork(compact);
CleanupCompaction(compact);
}
delete c;
if (status.ok()) {
// Done
} else if (shutting_down_.Acquire_Load()) {
// Ignore compaction errors found during shutting down
} else {
Log(env_, options_.info_log,
"Compaction error: %s", status.ToString().c_str());
if (options_.paranoid_checks && bg_error_.ok()) {
bg_error_ = status;
}
}
}
void DBImpl::CleanupCompaction(CompactionState* compact) {
mutex_.AssertHeld();
if (compact->builder != NULL) {
// May happen if we get a shutdown call in the middle of compaction
compact->builder->Abandon();
delete compact->builder;
} else {
assert(compact->outfile == NULL);
}
delete compact->outfile;
for (int i = 0; i < compact->outputs.size(); i++) {
const CompactionState::Output& out = compact->outputs[i];
pending_outputs_.erase(out.number);
}
delete compact;
}
Status DBImpl::OpenCompactionOutputFile(CompactionState* compact) {
assert(compact != NULL);
assert(compact->builder == NULL);
uint64_t file_number;
{
mutex_.Lock();
file_number = versions_->NewFileNumber();
pending_outputs_.insert(file_number);
CompactionState::Output out;
out.number = file_number;
out.smallest.Clear();
out.largest.Clear();
compact->outputs.push_back(out);
mutex_.Unlock();
}
// Make the output file
std::string fname = TableFileName(dbname_, file_number);
Status s = env_->NewWritableFile(fname, &compact->outfile);
if (s.ok()) {
compact->builder = new TableBuilder(options_, compact->outfile);
}
return s;
}
Status DBImpl::FinishCompactionOutputFile(CompactionState* compact,
Iterator* input) {
assert(compact != NULL);
assert(compact->outfile != NULL);
assert(compact->builder != NULL);
const uint64_t output_number = compact->current_output()->number;
assert(output_number != 0);
// Check for iterator errors
Status s = input->status();
const uint64_t current_entries = compact->builder->NumEntries();
if (s.ok()) {
s = compact->builder->Finish();
} else {
compact->builder->Abandon();
}
const uint64_t current_bytes = compact->builder->FileSize();
compact->current_output()->file_size = current_bytes;
compact->total_bytes += current_bytes;
delete compact->builder;
compact->builder = NULL;
// Finish and check for file errors
if (s.ok()) {
s = compact->outfile->Sync();
}
if (s.ok()) {
s = compact->outfile->Close();
}
delete compact->outfile;
compact->outfile = NULL;
if (s.ok() && current_entries > 0) {
// Verify that the table is usable
Iterator* iter = table_cache_->NewIterator(ReadOptions(),
output_number,
current_bytes);
s = iter->status();
delete iter;
if (s.ok()) {
Log(env_, options_.info_log,
"Generated table #%llu: %lld keys, %lld bytes",
(unsigned long long) output_number,
(unsigned long long) current_entries,
(unsigned long long) current_bytes);
}
}
return s;
}
Status DBImpl::InstallCompactionResults(CompactionState* compact) {
mutex_.AssertHeld();
Log(env_, options_.info_log, "Compacted %d@%d + %d@%d files => %lld bytes",
compact->compaction->num_input_files(0),
compact->compaction->level(),
compact->compaction->num_input_files(1),
compact->compaction->level() + 1,
static_cast<long long>(compact->total_bytes));
// Add compaction outputs
compact->compaction->AddInputDeletions(compact->compaction->edit());
const int level = compact->compaction->level();
for (int i = 0; i < compact->outputs.size(); i++) {
const CompactionState::Output& out = compact->outputs[i];
compact->compaction->edit()->AddFile(
level + 1,
out.number, out.file_size, out.smallest, out.largest);
pending_outputs_.erase(out.number);
}
compact->outputs.clear();
Status s = Install(compact->compaction->edit(), log_number_, NULL);
if (s.ok()) {
compact->compaction->ReleaseInputs();
DeleteObsoleteFiles();
} else {
// Discard any files we may have created during this failed compaction
for (int i = 0; i < compact->outputs.size(); i++) {
env_->DeleteFile(TableFileName(dbname_, compact->outputs[i].number));
}
}
return s;
}
Status DBImpl::DoCompactionWork(CompactionState* compact) {
Log(env_, options_.info_log, "Compacting %d@%d + %d@%d files",
compact->compaction->num_input_files(0),
compact->compaction->level(),
compact->compaction->num_input_files(1),
compact->compaction->level() + 1);
assert(versions_->NumLevelFiles(compact->compaction->level()) > 0);
assert(compact->builder == NULL);
assert(compact->outfile == NULL);
if (snapshots_.empty()) {
compact->smallest_snapshot = last_sequence_;
} else {
compact->smallest_snapshot = snapshots_.oldest()->number_;
}
// Release mutex while we're actually doing the compaction work
compacting_ = true;
mutex_.Unlock();
Iterator* input = versions_->MakeInputIterator(compact->compaction);
input->SeekToFirst();
Status status;
ParsedInternalKey ikey;
std::string current_user_key;
bool has_current_user_key = false;
SequenceNumber last_sequence_for_key = kMaxSequenceNumber;
for (; input->Valid() && !shutting_down_.Acquire_Load(); ) {
Slice key = input->key();
InternalKey tmp_internal_key;
tmp_internal_key.DecodeFrom(key);
if (compact->compaction->ShouldStopBefore(tmp_internal_key) &&
compact->builder != NULL) {
status = FinishCompactionOutputFile(compact, input);
if (!status.ok()) {
break;
}
}
// Handle key/value, add to state, etc.
bool drop = false;
if (!ParseInternalKey(key, &ikey)) {
// Do not hide error keys
current_user_key.clear();
has_current_user_key = false;
last_sequence_for_key = kMaxSequenceNumber;
} else {
if (!has_current_user_key ||
user_comparator()->Compare(ikey.user_key,
Slice(current_user_key)) != 0) {
// First occurrence of this user key
current_user_key.assign(ikey.user_key.data(), ikey.user_key.size());
has_current_user_key = true;
last_sequence_for_key = kMaxSequenceNumber;
}
if (last_sequence_for_key <= compact->smallest_snapshot) {
// Hidden by an newer entry for same user key
drop = true; // (A)
} else if (ikey.type == kTypeDeletion &&
ikey.sequence <= compact->smallest_snapshot &&
compact->compaction->IsBaseLevelForKey(ikey.user_key)) {
// For this user key:
// (1) there is no data in higher levels
// (2) data in lower levels will have larger sequence numbers
// (3) data in layers that are being compacted here and have
// smaller sequence numbers will be dropped in the next
// few iterations of this loop (by rule (A) above).
// Therefore this deletion marker is obsolete and can be dropped.
drop = true;
}
last_sequence_for_key = ikey.sequence;
}
#if 0
Log(env_, options_.info_log,
" Compact: %s, seq %d, type: %d %d, drop: %d, is_base: %d, "
"%d smallest_snapshot: %d",
ikey.user_key.ToString().c_str(),
(int)ikey.sequence, ikey.type, kTypeLargeValueRef, drop,
compact->compaction->IsBaseLevelForKey(ikey.user_key),
(int)last_sequence_for_key, (int)compact->smallest_snapshot);
#endif
if (!drop) {
// Open output file if necessary
if (compact->builder == NULL) {
status = OpenCompactionOutputFile(compact);
if (!status.ok()) {
break;
}
}
if (compact->builder->NumEntries() == 0) {
compact->current_output()->smallest.DecodeFrom(key);
}
compact->current_output()->largest.DecodeFrom(key);
if (ikey.type == kTypeLargeValueRef) {
if (input->value().size() != LargeValueRef::ByteSize()) {
if (options_.paranoid_checks) {
status = Status::Corruption("invalid large value ref");
break;
} else {
Log(env_, options_.info_log,
"compaction found invalid large value ref");
}
} else {
compact->compaction->edit()->AddLargeValueRef(
LargeValueRef::FromRef(input->value()),
compact->current_output()->number,
input->key());
compact->builder->Add(key, input->value());
}
} else {
compact->builder->Add(key, input->value());
}
// Close output file if it is big enough
if (compact->builder->FileSize() >=
compact->compaction->MaxOutputFileSize()) {
status = FinishCompactionOutputFile(compact, input);
if (!status.ok()) {
break;
}
}
}
input->Next();
}
if (status.ok() && shutting_down_.Acquire_Load()) {
status = Status::IOError("Deleting DB during compaction");
}
if (status.ok() && compact->builder != NULL) {
status = FinishCompactionOutputFile(compact, input);
}
if (status.ok()) {
status = input->status();
}
delete input;
input = NULL;
mutex_.Lock();
if (status.ok()) {
status = InstallCompactionResults(compact);
}
compacting_ = false;
compacting_cv_.SignalAll();
return status;
}
Iterator* DBImpl::NewInternalIterator(const ReadOptions& options,
SequenceNumber* latest_snapshot) {
mutex_.Lock();
*latest_snapshot = last_sequence_;
// Collect together all needed child iterators
std::vector<Iterator*> list;
list.push_back(mem_->NewIterator());
versions_->current()->AddIterators(options, &list);
Iterator* internal_iter =
NewMergingIterator(&internal_comparator_, &list[0], list.size());
versions_->current()->Ref();
internal_iter->RegisterCleanup(&DBImpl::Unref, this, versions_->current());
mutex_.Unlock();
return internal_iter;
}
Iterator* DBImpl::TEST_NewInternalIterator() {
SequenceNumber ignored;
return NewInternalIterator(ReadOptions(), &ignored);
}
int64_t DBImpl::TEST_MaxNextLevelOverlappingBytes() {
MutexLock l(&mutex_);
return versions_->MaxNextLevelOverlappingBytes();
}
Status DBImpl::Get(const ReadOptions& options,
const Slice& key,
std::string* value) {
// TODO(opt): faster implementation
Iterator* iter = NewIterator(options);
iter->Seek(key);
bool found = false;
if (iter->Valid() && user_comparator()->Compare(key, iter->key()) == 0) {
Slice v = iter->value();
value->assign(v.data(), v.size());
found = true;
}
// Non-OK iterator status trumps everything else
Status result = iter->status();
if (result.ok() && !found) {
result = Status::NotFound(Slice()); // Use an empty error message for speed
}
delete iter;
return result;
}
Iterator* DBImpl::NewIterator(const ReadOptions& options) {
SequenceNumber latest_snapshot;
Iterator* internal_iter = NewInternalIterator(options, &latest_snapshot);
SequenceNumber sequence =
(options.snapshot ? options.snapshot->number_ : latest_snapshot);
return NewDBIterator(&dbname_, env_,
user_comparator(), internal_iter, sequence);
}
void DBImpl::Unref(void* arg1, void* arg2) {
DBImpl* impl = reinterpret_cast<DBImpl*>(arg1);
Version* v = reinterpret_cast<Version*>(arg2);
MutexLock l(&impl->mutex_);
v->Unref();
}
const Snapshot* DBImpl::GetSnapshot() {
MutexLock l(&mutex_);
return snapshots_.New(last_sequence_);
}
void DBImpl::ReleaseSnapshot(const Snapshot* s) {
MutexLock l(&mutex_);
snapshots_.Delete(s);
}
// Convenience methods
Status DBImpl::Put(const WriteOptions& o, const Slice& key, const Slice& val) {
return DB::Put(o, key, val);
}
Status DBImpl::Delete(const WriteOptions& options, const Slice& key) {
return DB::Delete(options, key);
}
Status DBImpl::Write(const WriteOptions& options, WriteBatch* updates) {
Status status;
WriteBatch* final = NULL;
{
MutexLock l(&mutex_);
if (!bg_error_.ok()) {
status = bg_error_;
} else if (mem_->ApproximateMemoryUsage() > options_.write_buffer_size) {
status = CompactMemTable();
}
if (status.ok()) {
status = HandleLargeValues(last_sequence_ + 1, updates, &final);
}
if (status.ok()) {
WriteBatchInternal::SetSequence(final, last_sequence_ + 1);
last_sequence_ += WriteBatchInternal::Count(final);
// Add to log and apply to memtable
status = log_->AddRecord(WriteBatchInternal::Contents(final));
if (status.ok() && options.sync) {
status = logfile_->Sync();
}
if (status.ok()) {
status = WriteBatchInternal::InsertInto(final, mem_);
}
}
if (options.post_write_snapshot != NULL) {
*options.post_write_snapshot =
status.ok() ? snapshots_.New(last_sequence_) : NULL;
}
}
if (final != updates) {
delete final;
}
return status;
}
bool DBImpl::HasLargeValues(const WriteBatch& batch) const {
if (WriteBatchInternal::ByteSize(&batch) >= options_.large_value_threshold) {
for (WriteBatchInternal::Iterator it(batch); !it.Done(); it.Next()) {
if (it.op() == kTypeValue &&
it.value().size() >= options_.large_value_threshold) {
return true;
}
}
}
return false;
}
// Given "raw_value", determines the appropriate compression format to use
// and stores the data that should be written to the large value file in
// "*file_bytes", and sets "*ref" to the appropriate large value reference.
// May use "*scratch" as backing store for "*file_bytes".
void DBImpl::MaybeCompressLargeValue(
const Slice& raw_value,
Slice* file_bytes,
std::string* scratch,
LargeValueRef* ref) {
switch (options_.compression) {
case kSnappyCompression: {
if (port::Snappy_Compress(raw_value.data(), raw_value.size(), scratch) &&
(scratch->size() < (raw_value.size() / 8) * 7)) {
*file_bytes = *scratch;
*ref = LargeValueRef::Make(raw_value, kSnappyCompression);
return;
}
// Less than 12.5% compression: just leave as uncompressed data
break;
}
case kNoCompression:
// Use default code outside of switch
break;
}
// Store as uncompressed data
*file_bytes = raw_value;
*ref = LargeValueRef::Make(raw_value, kNoCompression);
}
Status DBImpl::HandleLargeValues(SequenceNumber assigned_seq,
WriteBatch* updates,
WriteBatch** final) {
if (!HasLargeValues(*updates)) {
// Fast path: no large values found
*final = updates;
} else {
// Copy *updates to a new WriteBatch, replacing the references to
*final = new WriteBatch;
SequenceNumber seq = assigned_seq;
for (WriteBatchInternal::Iterator it(*updates); !it.Done(); it.Next()) {
switch (it.op()) {
case kTypeValue:
if (it.value().size() < options_.large_value_threshold) {
(*final)->Put(it.key(), it.value());
} else {
std::string scratch;
Slice file_bytes;
LargeValueRef large_ref;
MaybeCompressLargeValue(
it.value(), &file_bytes, &scratch, &large_ref);
InternalKey ikey(it.key(), seq, kTypeLargeValueRef);
if (versions_->RegisterLargeValueRef(large_ref, log_number_,ikey)) {
// TODO(opt): avoid holding the lock here (but be careful about
// another thread doing a Write and changing log_number_ or
// having us get a different "assigned_seq" value).
uint64_t tmp_number = versions_->NewFileNumber();
pending_outputs_.insert(tmp_number);
std::string tmp = TempFileName(dbname_, tmp_number);
WritableFile* file;
Status s = env_->NewWritableFile(tmp, &file);
if (!s.ok()) {
return s; // Caller will delete *final
}
file->Append(file_bytes);
s = file->Close();
delete file;
if (s.ok()) {
const std::string fname =
LargeValueFileName(dbname_, large_ref);
s = env_->RenameFile(tmp, fname);
} else {
Log(env_, options_.info_log, "Write large value: %s",
s.ToString().c_str());
}
pending_outputs_.erase(tmp_number);
if (!s.ok()) {
env_->DeleteFile(tmp); // Cleanup; intentionally ignoring error
return s; // Caller will delete *final
}
}
// Put an indirect reference in the write batch in place
// of large value
WriteBatchInternal::PutLargeValueRef(*final, it.key(), large_ref);
}
break;
case kTypeLargeValueRef:
return Status::Corruption("Corrupted write batch");
break;
case kTypeDeletion:
(*final)->Delete(it.key());
break;
}
seq = seq + 1;
}
}
return Status::OK();
}
bool DBImpl::GetProperty(const Slice& property, uint64_t* value) {
MutexLock l(&mutex_);
Slice in = property;
Slice prefix("leveldb.");
if (!in.starts_with(prefix)) return false;
in.remove_prefix(prefix.size());
if (in.starts_with("num-files-at-level")) {
in.remove_prefix(strlen("num-files-at-level"));
uint64_t level;
bool ok = ConsumeDecimalNumber(&in, &level) && in.empty();
if (!ok || level < 0 || level >= config::kNumLevels) {
return false;
} else {
*value = versions_->NumLevelFiles(level);
return true;
}
}
return false;
}
void DBImpl::GetApproximateSizes(
const Range* range, int n,
uint64_t* sizes) {
// TODO(opt): better implementation
Version* v;
{
MutexLock l(&mutex_);
versions_->current()->Ref();
v = versions_->current();
}
for (int i = 0; i < n; i++) {
// Convert user_key into a corresponding internal key.
InternalKey k1(range[i].start, kMaxSequenceNumber, kValueTypeForSeek);
InternalKey k2(range[i].limit, kMaxSequenceNumber, kValueTypeForSeek);
uint64_t start = versions_->ApproximateOffsetOf(v, k1);
uint64_t limit = versions_->ApproximateOffsetOf(v, k2);
sizes[i] = (limit >= start ? limit - start : 0);
}
{
MutexLock l(&mutex_);
v->Unref();
}
}
// Default implementations of convenience methods that subclasses of DB
// can call if they wish
Status DB::Put(const WriteOptions& opt, const Slice& key, const Slice& value) {
WriteBatch batch;
batch.Put(key, value);
return Write(opt, &batch);
}
Status DB::Delete(const WriteOptions& opt, const Slice& key) {
WriteBatch batch;
batch.Delete(key);
return Write(opt, &batch);
}
DB::~DB() { }
Status DB::Open(const Options& options, const std::string& dbname,
DB** dbptr) {
*dbptr = NULL;
DBImpl* impl = new DBImpl(options, dbname);
impl->mutex_.Lock();
VersionEdit edit;
Status s = impl->Recover(&edit); // Handles create_if_missing, error_if_exists
if (s.ok()) {
impl->log_number_ = impl->versions_->NewFileNumber();
WritableFile* lfile;
s = options.env->NewWritableFile(LogFileName(dbname, impl->log_number_),
&lfile);
if (s.ok()) {
impl->logfile_ = lfile;
impl->log_ = new log::Writer(lfile);
s = impl->Install(&edit, impl->log_number_, NULL);
}
if (s.ok()) {
impl->DeleteObsoleteFiles();
}
}
impl->mutex_.Unlock();
if (s.ok()) {
*dbptr = impl;
} else {
delete impl;
}
return s;
}
Status DestroyDB(const std::string& dbname, const Options& options) {
Env* env = options.env;
std::vector<std::string> filenames;
// Ignore error in case directory does not exist
env->GetChildren(dbname, &filenames);
if (filenames.empty()) {
return Status::OK();
}
FileLock* lock;
Status result = env->LockFile(LockFileName(dbname), &lock);
if (result.ok()) {
uint64_t number;
LargeValueRef large_ref;
FileType type;
for (int i = 0; i < filenames.size(); i++) {
if (ParseFileName(filenames[i], &number, &large_ref, &type)) {
Status del = env->DeleteFile(dbname + "/" + filenames[i]);
if (result.ok() && !del.ok()) {
result = del;
}
}
}
env->UnlockFile(lock); // Ignore error since state is already gone
env->DeleteFile(LockFileName(dbname));
env->DeleteDir(dbname); // Ignore error in case dir contains other files
}
return result;
}
}
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