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rocksdb/utilities/transactions/write_unprepared_txn.cc

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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
#ifndef ROCKSDB_LITE
#include "utilities/transactions/write_unprepared_txn.h"
#include "db/db_impl/db_impl.h"
#include "util/cast_util.h"
#include "utilities/transactions/write_unprepared_txn_db.h"
namespace rocksdb {
bool WriteUnpreparedTxnReadCallback::IsVisibleFullCheck(SequenceNumber seq) {
// Since unprep_seqs maps prep_seq => prepare_batch_cnt, to check if seq is
// in unprep_seqs, we have to check if seq is equal to prep_seq or any of
// the prepare_batch_cnt seq nums after it.
//
// TODO(lth): Can be optimized with std::lower_bound if unprep_seqs is
// large.
for (const auto& it : unprep_seqs_) {
if (it.first <= seq && seq < it.first + it.second) {
return true;
}
}
bool snap_released = false;
auto ret =
db_->IsInSnapshot(seq, wup_snapshot_, min_uncommitted_, &snap_released);
assert(!snap_released || backed_by_snapshot_ == kUnbackedByDBSnapshot);
snap_released_ |= snap_released;
return ret;
}
WriteUnpreparedTxn::WriteUnpreparedTxn(WriteUnpreparedTxnDB* txn_db,
const WriteOptions& write_options,
const TransactionOptions& txn_options)
: WritePreparedTxn(txn_db, write_options, txn_options),
wupt_db_(txn_db),
last_log_number_(0),
recovered_txn_(false),
largest_validated_seq_(0) {
if (txn_options.write_batch_flush_threshold < 0) {
write_batch_flush_threshold_ =
txn_db_impl_->GetTxnDBOptions().default_write_batch_flush_threshold;
} else {
write_batch_flush_threshold_ = txn_options.write_batch_flush_threshold;
}
}
WriteUnpreparedTxn::~WriteUnpreparedTxn() {
if (!unprep_seqs_.empty()) {
assert(log_number_ > 0);
assert(GetId() > 0);
assert(!name_.empty());
// We should rollback regardless of GetState, but some unit tests that
// test crash recovery run the destructor assuming that rollback does not
// happen, so that rollback during recovery can be exercised.
if (GetState() == STARTED || GetState() == LOCKS_STOLEN) {
auto s = RollbackInternal();
assert(s.ok());
if (!s.ok()) {
ROCKS_LOG_FATAL(
wupt_db_->info_log_,
"Rollback of WriteUnprepared transaction failed in destructor: %s",
s.ToString().c_str());
}
dbimpl_->logs_with_prep_tracker()->MarkLogAsHavingPrepSectionFlushed(
log_number_);
}
}
// Call tracked_keys_.clear() so that ~PessimisticTransaction does not
// try to unlock keys for recovered transactions.
if (recovered_txn_) {
tracked_keys_.clear();
}
}
void WriteUnpreparedTxn::Initialize(const TransactionOptions& txn_options) {
PessimisticTransaction::Initialize(txn_options);
if (txn_options.write_batch_flush_threshold < 0) {
write_batch_flush_threshold_ =
txn_db_impl_->GetTxnDBOptions().default_write_batch_flush_threshold;
} else {
write_batch_flush_threshold_ = txn_options.write_batch_flush_threshold;
}
unprep_seqs_.clear();
flushed_save_points_.reset(nullptr);
unflushed_save_points_.reset(nullptr);
recovered_txn_ = false;
largest_validated_seq_ = 0;
assert(active_iterators_.empty());
active_iterators_.clear();
untracked_keys_.clear();
}
Status WriteUnpreparedTxn::HandleWrite(std::function<Status()> do_write) {
Status s;
if (active_iterators_.empty()) {
s = MaybeFlushWriteBatchToDB();
if (!s.ok()) {
return s;
}
}
s = do_write();
if (s.ok()) {
if (snapshot_) {
largest_validated_seq_ =
std::max(largest_validated_seq_, snapshot_->GetSequenceNumber());
} else {
// TODO(lth): We should use the same number as tracked_at_seq in TryLock,
// because what is actually being tracked is the sequence number at which
// this key was locked at.
largest_validated_seq_ = db_impl_->GetLastPublishedSequence();
}
}
return s;
}
Status WriteUnpreparedTxn::Put(ColumnFamilyHandle* column_family,
const Slice& key, const Slice& value,
const bool assume_tracked) {
return HandleWrite([&]() {
return TransactionBaseImpl::Put(column_family, key, value, assume_tracked);
});
}
Status WriteUnpreparedTxn::Put(ColumnFamilyHandle* column_family,
const SliceParts& key, const SliceParts& value,
const bool assume_tracked) {
return HandleWrite([&]() {
return TransactionBaseImpl::Put(column_family, key, value, assume_tracked);
});
}
Status WriteUnpreparedTxn::Merge(ColumnFamilyHandle* column_family,
const Slice& key, const Slice& value,
const bool assume_tracked) {
return HandleWrite([&]() {
return TransactionBaseImpl::Merge(column_family, key, value,
assume_tracked);
});
}
Status WriteUnpreparedTxn::Delete(ColumnFamilyHandle* column_family,
const Slice& key, const bool assume_tracked) {
return HandleWrite([&]() {
return TransactionBaseImpl::Delete(column_family, key, assume_tracked);
});
}
Status WriteUnpreparedTxn::Delete(ColumnFamilyHandle* column_family,
const SliceParts& key,
const bool assume_tracked) {
return HandleWrite([&]() {
return TransactionBaseImpl::Delete(column_family, key, assume_tracked);
});
}
Status WriteUnpreparedTxn::SingleDelete(ColumnFamilyHandle* column_family,
const Slice& key,
const bool assume_tracked) {
return HandleWrite([&]() {
return TransactionBaseImpl::SingleDelete(column_family, key,
assume_tracked);
});
}
Status WriteUnpreparedTxn::SingleDelete(ColumnFamilyHandle* column_family,
const SliceParts& key,
const bool assume_tracked) {
return HandleWrite([&]() {
return TransactionBaseImpl::SingleDelete(column_family, key,
assume_tracked);
});
}
// WriteUnpreparedTxn::RebuildFromWriteBatch is only called on recovery. For
// WriteUnprepared, the write batches have already been written into the
// database during WAL replay, so all we have to do is just to "retrack" the key
// so that rollbacks are possible.
//
// Calling TryLock instead of TrackKey is also possible, but as an optimization,
// recovered transactions do not hold locks on their keys. This follows the
// implementation in PessimisticTransactionDB::Initialize where we set
// skip_concurrency_control to true.
Status WriteUnpreparedTxn::RebuildFromWriteBatch(WriteBatch* wb) {
struct TrackKeyHandler : public WriteBatch::Handler {
WriteUnpreparedTxn* txn_;
bool rollback_merge_operands_;
TrackKeyHandler(WriteUnpreparedTxn* txn, bool rollback_merge_operands)
: txn_(txn), rollback_merge_operands_(rollback_merge_operands) {}
Status PutCF(uint32_t cf, const Slice& key, const Slice&) override {
txn_->TrackKey(cf, key.ToString(), kMaxSequenceNumber,
false /* read_only */, true /* exclusive */);
return Status::OK();
}
Status DeleteCF(uint32_t cf, const Slice& key) override {
txn_->TrackKey(cf, key.ToString(), kMaxSequenceNumber,
false /* read_only */, true /* exclusive */);
return Status::OK();
}
Status SingleDeleteCF(uint32_t cf, const Slice& key) override {
txn_->TrackKey(cf, key.ToString(), kMaxSequenceNumber,
false /* read_only */, true /* exclusive */);
return Status::OK();
}
Status MergeCF(uint32_t cf, const Slice& key, const Slice&) override {
if (rollback_merge_operands_) {
txn_->TrackKey(cf, key.ToString(), kMaxSequenceNumber,
false /* read_only */, true /* exclusive */);
}
return Status::OK();
}
// Recovered batches do not contain 2PC markers.
Status MarkBeginPrepare(bool) override { return Status::InvalidArgument(); }
Status MarkEndPrepare(const Slice&) override {
return Status::InvalidArgument();
}
Status MarkNoop(bool) override { return Status::InvalidArgument(); }
Status MarkCommit(const Slice&) override {
return Status::InvalidArgument();
}
Status MarkRollback(const Slice&) override {
return Status::InvalidArgument();
}
};
TrackKeyHandler handler(this,
wupt_db_->txn_db_options_.rollback_merge_operands);
return wb->Iterate(&handler);
}
Status WriteUnpreparedTxn::MaybeFlushWriteBatchToDB() {
const bool kPrepared = true;
Status s;
if (write_batch_flush_threshold_ > 0 &&
write_batch_.GetWriteBatch()->Count() > 0 &&
write_batch_.GetDataSize() >
static_cast<size_t>(write_batch_flush_threshold_)) {
assert(GetState() != PREPARED);
s = FlushWriteBatchToDB(!kPrepared);
}
return s;
}
Status WriteUnpreparedTxn::FlushWriteBatchToDB(bool prepared) {
// If the current write batch contains savepoints, then some special handling
// is required so that RollbackToSavepoint can work.
//
// RollbackToSavepoint is not supported after Prepare() is called, so only do
// this for unprepared batches.
if (!prepared && unflushed_save_points_ != nullptr &&
!unflushed_save_points_->empty()) {
return FlushWriteBatchWithSavePointToDB();
}
return FlushWriteBatchToDBInternal(prepared);
}
Status WriteUnpreparedTxn::FlushWriteBatchToDBInternal(bool prepared) {
if (name_.empty()) {
assert(!prepared);
#ifndef NDEBUG
static std::atomic_ullong autogen_id{0};
// To avoid changing all tests to call SetName, just autogenerate one.
if (wupt_db_->txn_db_options_.autogenerate_name) {
SetName(std::string("autoxid") + ToString(autogen_id.fetch_add(1)));
} else
#endif
{
return Status::InvalidArgument("Cannot write to DB without SetName.");
}
}
struct UntrackedKeyHandler : public WriteBatch::Handler {
WriteUnpreparedTxn* txn_;
bool rollback_merge_operands_;
UntrackedKeyHandler(WriteUnpreparedTxn* txn, bool rollback_merge_operands)
: txn_(txn), rollback_merge_operands_(rollback_merge_operands) {}
Status AddUntrackedKey(uint32_t cf, const Slice& key) {
auto str = key.ToString();
if (txn_->tracked_keys_[cf].count(str) == 0) {
txn_->untracked_keys_[cf].push_back(str);
}
return Status::OK();
}
Status PutCF(uint32_t cf, const Slice& key, const Slice&) override {
return AddUntrackedKey(cf, key);
}
Status DeleteCF(uint32_t cf, const Slice& key) override {
return AddUntrackedKey(cf, key);
}
Status SingleDeleteCF(uint32_t cf, const Slice& key) override {
return AddUntrackedKey(cf, key);
}
Status MergeCF(uint32_t cf, const Slice& key, const Slice&) override {
if (rollback_merge_operands_) {
return AddUntrackedKey(cf, key);
}
return Status::OK();
}
// The only expected 2PC marker is the initial Noop marker.
Status MarkNoop(bool empty_batch) override {
return empty_batch ? Status::OK() : Status::InvalidArgument();
}
Status MarkBeginPrepare(bool) override { return Status::InvalidArgument(); }
Status MarkEndPrepare(const Slice&) override {
return Status::InvalidArgument();
}
Status MarkCommit(const Slice&) override {
return Status::InvalidArgument();
}
Status MarkRollback(const Slice&) override {
return Status::InvalidArgument();
}
};
UntrackedKeyHandler handler(
this, wupt_db_->txn_db_options_.rollback_merge_operands);
auto s = GetWriteBatch()->GetWriteBatch()->Iterate(&handler);
assert(s.ok());
// TODO(lth): Reduce duplicate code with WritePrepared prepare logic.
WriteOptions write_options = write_options_;
write_options.disableWAL = false;
const bool WRITE_AFTER_COMMIT = true;
const bool first_prepare_batch = log_number_ == 0;
// MarkEndPrepare will change Noop marker to the appropriate marker.
WriteBatchInternal::MarkEndPrepare(GetWriteBatch()->GetWriteBatch(), name_,
!WRITE_AFTER_COMMIT, !prepared);
// For each duplicate key we account for a new sub-batch
prepare_batch_cnt_ = GetWriteBatch()->SubBatchCnt();
// AddPrepared better to be called in the pre-release callback otherwise there
// is a non-zero chance of max advancing prepare_seq and readers assume the
// data as committed.
// Also having it in the PreReleaseCallback allows in-order addition of
// prepared entries to PreparedHeap and hence enables an optimization. Refer
// to SmallestUnCommittedSeq for more details.
AddPreparedCallback add_prepared_callback(
wpt_db_, db_impl_, prepare_batch_cnt_,
db_impl_->immutable_db_options().two_write_queues, first_prepare_batch);
const bool DISABLE_MEMTABLE = true;
uint64_t seq_used = kMaxSequenceNumber;
// log_number_ should refer to the oldest log containing uncommitted data
// from the current transaction. This means that if log_number_ is set,
// WriteImpl should not overwrite that value, so set log_used to nullptr if
// log_number_ is already set.
s = db_impl_->WriteImpl(write_options, GetWriteBatch()->GetWriteBatch(),
/*callback*/ nullptr, &last_log_number_,
/*log ref*/ 0, !DISABLE_MEMTABLE, &seq_used,
prepare_batch_cnt_, &add_prepared_callback);
if (log_number_ == 0) {
log_number_ = last_log_number_;
}
assert(!s.ok() || seq_used != kMaxSequenceNumber);
auto prepare_seq = seq_used;
// Only call SetId if it hasn't been set yet.
if (GetId() == 0) {
SetId(prepare_seq);
}
// unprep_seqs_ will also contain prepared seqnos since they are treated in
// the same way in the prepare/commit callbacks. See the comment on the
// definition of unprep_seqs_.
unprep_seqs_[prepare_seq] = prepare_batch_cnt_;
// Reset transaction state.
if (!prepared) {
prepare_batch_cnt_ = 0;
const bool kClear = true;
TransactionBaseImpl::InitWriteBatch(kClear);
}
return s;
}
Status WriteUnpreparedTxn::FlushWriteBatchWithSavePointToDB() {
assert(unflushed_save_points_ != nullptr &&
unflushed_save_points_->size() > 0);
assert(save_points_ != nullptr && save_points_->size() > 0);
assert(save_points_->size() >= unflushed_save_points_->size());
// Handler class for creating an unprepared batch from a savepoint.
struct SavePointBatchHandler : public WriteBatch::Handler {
WriteBatchWithIndex* wb_;
const std::map<uint32_t, ColumnFamilyHandle*>& handles_;
SavePointBatchHandler(
WriteBatchWithIndex* wb,
const std::map<uint32_t, ColumnFamilyHandle*>& handles)
: wb_(wb), handles_(handles) {}
Status PutCF(uint32_t cf, const Slice& key, const Slice& value) override {
return wb_->Put(handles_.at(cf), key, value);
}
Status DeleteCF(uint32_t cf, const Slice& key) override {
return wb_->Delete(handles_.at(cf), key);
}
Status SingleDeleteCF(uint32_t cf, const Slice& key) override {
return wb_->SingleDelete(handles_.at(cf), key);
}
Status MergeCF(uint32_t cf, const Slice& key, const Slice& value) override {
return wb_->Merge(handles_.at(cf), key, value);
}
// The only expected 2PC marker is the initial Noop marker.
Status MarkNoop(bool empty_batch) override {
return empty_batch ? Status::OK() : Status::InvalidArgument();
}
Status MarkBeginPrepare(bool) override { return Status::InvalidArgument(); }
Status MarkEndPrepare(const Slice&) override {
return Status::InvalidArgument();
}
Status MarkCommit(const Slice&) override {
return Status::InvalidArgument();
}
Status MarkRollback(const Slice&) override {
return Status::InvalidArgument();
}
};
// The comparator of the default cf is passed in, similar to the
// initialization of TransactionBaseImpl::write_batch_. This comparator is
// only used if the write batch encounters an invalid cf id, and falls back to
// this comparator.
WriteBatchWithIndex wb(wpt_db_->DefaultColumnFamily()->GetComparator(), 0,
true, 0);
// Swap with write_batch_ so that wb contains the complete write batch. The
// actual write batch that will be flushed to DB will be built in
// write_batch_, and will be read by FlushWriteBatchToDBInternal.
std::swap(wb, write_batch_);
TransactionBaseImpl::InitWriteBatch();
size_t prev_boundary = WriteBatchInternal::kHeader;
const bool kPrepared = true;
for (size_t i = 0; i < unflushed_save_points_->size() + 1; i++) {
bool trailing_batch = i == unflushed_save_points_->size();
SavePointBatchHandler sp_handler(&write_batch_,
*wupt_db_->GetCFHandleMap().get());
size_t curr_boundary = trailing_batch ? wb.GetWriteBatch()->GetDataSize()
: (*unflushed_save_points_)[i];
// Construct the partial write batch up to the savepoint.
//
// Theoretically, a memcpy between the write batches should be sufficient
// since the rewriting into the batch should produce the exact same byte
// representation. Rebuilding the WriteBatchWithIndex index is still
// necessary though, and would imply doing two passes over the batch though.
Status s = WriteBatchInternal::Iterate(wb.GetWriteBatch(), &sp_handler,
prev_boundary, curr_boundary);
if (!s.ok()) {
return s;
}
if (write_batch_.GetWriteBatch()->Count() > 0) {
// Flush the write batch.
s = FlushWriteBatchToDBInternal(!kPrepared);
if (!s.ok()) {
return s;
}
}
if (!trailing_batch) {
if (flushed_save_points_ == nullptr) {
flushed_save_points_.reset(
new autovector<WriteUnpreparedTxn::SavePoint>());
}
flushed_save_points_->emplace_back(
unprep_seqs_, new ManagedSnapshot(db_impl_, wupt_db_->GetSnapshot()));
}
prev_boundary = curr_boundary;
const bool kClear = true;
TransactionBaseImpl::InitWriteBatch(kClear);
}
unflushed_save_points_->clear();
return Status::OK();
}
Status WriteUnpreparedTxn::PrepareInternal() {
const bool kPrepared = true;
return FlushWriteBatchToDB(kPrepared);
}
Status WriteUnpreparedTxn::CommitWithoutPrepareInternal() {
if (unprep_seqs_.empty()) {
assert(log_number_ == 0);
assert(GetId() == 0);
return WritePreparedTxn::CommitWithoutPrepareInternal();
}
// TODO(lth): We should optimize commit without prepare to not perform
// a prepare under the hood.
auto s = PrepareInternal();
if (!s.ok()) {
return s;
}
return CommitInternal();
}
Status WriteUnpreparedTxn::CommitInternal() {
// TODO(lth): Reduce duplicate code with WritePrepared commit logic.
// We take the commit-time batch and append the Commit marker. The Memtable
// will ignore the Commit marker in non-recovery mode
WriteBatch* working_batch = GetCommitTimeWriteBatch();
const bool empty = working_batch->Count() == 0;
WriteBatchInternal::MarkCommit(working_batch, name_);
const bool for_recovery = use_only_the_last_commit_time_batch_for_recovery_;
if (!empty && for_recovery) {
// When not writing to memtable, we can still cache the latest write batch.
// The cached batch will be written to memtable in WriteRecoverableState
// during FlushMemTable
WriteBatchInternal::SetAsLastestPersistentState(working_batch);
}
const bool includes_data = !empty && !for_recovery;
size_t commit_batch_cnt = 0;
if (UNLIKELY(includes_data)) {
ROCKS_LOG_WARN(db_impl_->immutable_db_options().info_log,
"Duplicate key overhead");
SubBatchCounter counter(*wpt_db_->GetCFComparatorMap());
auto s = working_batch->Iterate(&counter);
assert(s.ok());
commit_batch_cnt = counter.BatchCount();
}
const bool disable_memtable = !includes_data;
const bool do_one_write =
!db_impl_->immutable_db_options().two_write_queues || disable_memtable;
WriteUnpreparedCommitEntryPreReleaseCallback update_commit_map(
wpt_db_, db_impl_, unprep_seqs_, commit_batch_cnt);
const bool kFirstPrepareBatch = true;
AddPreparedCallback add_prepared_callback(
wpt_db_, db_impl_, commit_batch_cnt,
db_impl_->immutable_db_options().two_write_queues, !kFirstPrepareBatch);
PreReleaseCallback* pre_release_callback;
if (do_one_write) {
pre_release_callback = &update_commit_map;
} else {
pre_release_callback = &add_prepared_callback;
}
uint64_t seq_used = kMaxSequenceNumber;
// Since the prepared batch is directly written to memtable, there is
// already a connection between the memtable and its WAL, so there is no
// need to redundantly reference the log that contains the prepared data.
const uint64_t zero_log_number = 0ull;
size_t batch_cnt = UNLIKELY(commit_batch_cnt) ? commit_batch_cnt : 1;
auto s = db_impl_->WriteImpl(write_options_, working_batch, nullptr, nullptr,
zero_log_number, disable_memtable, &seq_used,
batch_cnt, pre_release_callback);
assert(!s.ok() || seq_used != kMaxSequenceNumber);
const SequenceNumber commit_batch_seq = seq_used;
if (LIKELY(do_one_write || !s.ok())) {
if (LIKELY(s.ok())) {
// Note RemovePrepared should be called after WriteImpl that publishsed
// the seq. Otherwise SmallestUnCommittedSeq optimization breaks.
for (const auto& seq : unprep_seqs_) {
wpt_db_->RemovePrepared(seq.first, seq.second);
}
}
if (UNLIKELY(!do_one_write)) {
wpt_db_->RemovePrepared(commit_batch_seq, commit_batch_cnt);
}
unprep_seqs_.clear();
flushed_save_points_.reset(nullptr);
unflushed_save_points_.reset(nullptr);
return s;
} // else do the 2nd write to publish seq
// Populate unprep_seqs_ with commit_batch_seq, since we treat data in the
// commit write batch as just another "unprepared" batch. This will also
// update the unprep_seqs_ in the update_commit_map callback.
unprep_seqs_[commit_batch_seq] = commit_batch_cnt;
// Note: the 2nd write comes with a performance penality. So if we have too
// many of commits accompanied with ComitTimeWriteBatch and yet we cannot
// enable use_only_the_last_commit_time_batch_for_recovery_ optimization,
// two_write_queues should be disabled to avoid many additional writes here.
// Update commit map only from the 2nd queue
WriteBatch empty_batch;
empty_batch.PutLogData(Slice());
// In the absence of Prepare markers, use Noop as a batch separator
WriteBatchInternal::InsertNoop(&empty_batch);
const bool DISABLE_MEMTABLE = true;
const size_t ONE_BATCH = 1;
const uint64_t NO_REF_LOG = 0;
s = db_impl_->WriteImpl(write_options_, &empty_batch, nullptr, nullptr,
NO_REF_LOG, DISABLE_MEMTABLE, &seq_used, ONE_BATCH,
&update_commit_map);
assert(!s.ok() || seq_used != kMaxSequenceNumber);
// Note RemovePrepared should be called after WriteImpl that publishsed the
// seq. Otherwise SmallestUnCommittedSeq optimization breaks.
for (const auto& seq : unprep_seqs_) {
wpt_db_->RemovePrepared(seq.first, seq.second);
}
unprep_seqs_.clear();
flushed_save_points_.reset(nullptr);
unflushed_save_points_.reset(nullptr);
return s;
}
Status WriteUnpreparedTxn::WriteRollbackKeys(
const TransactionKeyMap& tracked_keys, WriteBatchWithIndex* rollback_batch,
ReadCallback* callback, const ReadOptions& roptions) {
const auto& cf_map = *wupt_db_->GetCFHandleMap();
auto WriteRollbackKey = [&](const std::string& key, uint32_t cfid) {
const auto& cf_handle = cf_map.at(cfid);
PinnableSlice pinnable_val;
bool not_used;
DBImpl::GetImplOptions get_impl_options;
get_impl_options.column_family = cf_handle;
get_impl_options.value = &pinnable_val;
get_impl_options.value_found = &not_used;
get_impl_options.callback = callback;
auto s = db_impl_->GetImpl(roptions, key, get_impl_options);
if (s.ok()) {
s = rollback_batch->Put(cf_handle, key, pinnable_val);
assert(s.ok());
} else if (s.IsNotFound()) {
s = rollback_batch->Delete(cf_handle, key);
assert(s.ok());
} else {
return s;
}
return Status::OK();
};
for (const auto& cfkey : tracked_keys) {
const auto cfid = cfkey.first;
const auto& keys = cfkey.second;
for (const auto& pair : keys) {
auto s = WriteRollbackKey(pair.first, cfid);
if (!s.ok()) {
return s;
}
}
}
for (const auto& cfkey : untracked_keys_) {
const auto cfid = cfkey.first;
const auto& keys = cfkey.second;
for (const auto& key : keys) {
auto s = WriteRollbackKey(key, cfid);
if (!s.ok()) {
return s;
}
}
}
return Status::OK();
}
Status WriteUnpreparedTxn::RollbackInternal() {
// TODO(lth): Reduce duplicate code with WritePrepared rollback logic.
WriteBatchWithIndex rollback_batch(
wpt_db_->DefaultColumnFamily()->GetComparator(), 0, true, 0);
assert(GetId() != kMaxSequenceNumber);
assert(GetId() > 0);
Status s;
WritePrepared: Report released snapshots in IsInSnapshot (#4856) Summary: Previously IsInSnapshot assumed that the snapshot is valid at the time that the function is called. However there are cases where that might not be valid. Example is background compactions where the compaction algorithm operates with a list of snapshots some of which might be released by the time they are being passed to IsInSnapshot. The patch make two changes to enable the caller to tell difference: i) any live snapshot below max is added to max_committed_seq_, which allows IsInSnapshot to confidently tell whether the passed snapshot is invalid if it below max, ii) extends IsInSnapshot API with a "released" variable that is set true when IsInSnapshot find no such snapshot below max and also find no other way to give a certain return value. In such cases the return value is true but the caller should also check the "released" boolean after the call. In short here is the changes in the API: i) If the snapshot is valid, no change is required. ii) If the snapshot might be invalid, a reference to "released" boolean must be passed to IsInSnapshot. ii-a) If snapshot is above max, IsInSnapshot can figure the return valid using the commit cache. ii-b) otherwise if snapshot is in old_commit_map_, IsInSnapshot can use that to tell if value was visible to the snapshot. ii-c) otherwise it sets "released" to true and returns true as well. Pull Request resolved: https://github.com/facebook/rocksdb/pull/4856 Differential Revision: D13599847 Pulled By: maysamyabandeh fbshipit-source-id: 1752be28667f886a1efec8cae5714b9b7a8f1e0f
6 years ago
auto read_at_seq = kMaxSequenceNumber;
ReadOptions roptions;
// to prevent callback's seq to be overrriden inside DBImpk::Get
roptions.snapshot = wpt_db_->GetMaxSnapshot();
// Note that we do not use WriteUnpreparedTxnReadCallback because we do not
// need to read our own writes when reading prior versions of the key for
// rollback.
WriteUnPrepared: less virtual in iterator callback (#5049) Summary: WriteUnPrepared adds a virtual function, MaxUnpreparedSequenceNumber, to ReadCallback, which returns 0 unless WriteUnPrepared is enabled and the transaction has uncommitted data written to the DB. Together with snapshot sequence number, this determines the last sequence that is visible to reads. The patch clarifies the guarantees of the GetIterator API in WriteUnPrepared transactions and make use of that to statically initialize the read callback and thus avoid the virtual call. Furthermore it increases the minimum value for min_uncommitted from 0 to 1 as seq 0 is used only for last level keys that are committed in all snapshots. The following benchmark shows +0.26% higher throughput in seekrandom benchmark. Benchmark: ./db_bench --benchmarks=fillrandom --use_existing_db=0 --num=1000000 --db=/dev/shm/dbbench ./db_bench --benchmarks=seekrandom[X10] --use_existing_db=1 --db=/dev/shm/dbbench --num=1000000 --duration=60 --seek_nexts=100 seekrandom [AVG 10 runs] : 20355 ops/sec; 225.2 MB/sec seekrandom [MEDIAN 10 runs] : 20425 ops/sec; 225.9 MB/sec ./db_bench_lessvirtual3 --benchmarks=seekrandom[X10] --use_existing_db=1 --db=/dev/shm/dbbench --num=1000000 --duration=60 --seek_nexts=100 seekrandom [AVG 10 runs] : 20409 ops/sec; 225.8 MB/sec seekrandom [MEDIAN 10 runs] : 20487 ops/sec; 226.6 MB/sec Pull Request resolved: https://github.com/facebook/rocksdb/pull/5049 Differential Revision: D14366459 Pulled By: maysamyabandeh fbshipit-source-id: ebaff8908332a5ae9af7defeadabcb624be660ef
6 years ago
WritePreparedTxnReadCallback callback(wpt_db_, read_at_seq);
WriteRollbackKeys(GetTrackedKeys(), &rollback_batch, &callback, roptions);
// The Rollback marker will be used as a batch separator
WriteBatchInternal::MarkRollback(rollback_batch.GetWriteBatch(), name_);
bool do_one_write = !db_impl_->immutable_db_options().two_write_queues;
const bool DISABLE_MEMTABLE = true;
const uint64_t NO_REF_LOG = 0;
uint64_t seq_used = kMaxSequenceNumber;
// TODO(lth): We write rollback batch all in a single batch here, but this
// should be subdivded into multiple batches as well. In phase 2, when key
// sets are read from WAL, this will happen naturally.
const size_t ONE_BATCH = 1;
// We commit the rolled back prepared batches. ALthough this is
// counter-intuitive, i) it is safe to do so, since the prepared batches are
// already canceled out by the rollback batch, ii) adding the commit entry to
// CommitCache will allow us to benefit from the existing mechanism in
// CommitCache that keeps an entry evicted due to max advance and yet overlaps
// with a live snapshot around so that the live snapshot properly skips the
// entry even if its prepare seq is lower than max_evicted_seq_.
WriteUnpreparedCommitEntryPreReleaseCallback update_commit_map(
wpt_db_, db_impl_, unprep_seqs_, ONE_BATCH);
// Note: the rollback batch does not need AddPrepared since it is written to
// DB in one shot. min_uncommitted still works since it requires capturing
// data that is written to DB but not yet committed, while the roolback
// batch commits with PreReleaseCallback.
s = db_impl_->WriteImpl(write_options_, rollback_batch.GetWriteBatch(),
nullptr, nullptr, NO_REF_LOG, !DISABLE_MEMTABLE,
&seq_used, rollback_batch.SubBatchCnt(),
do_one_write ? &update_commit_map : nullptr);
assert(!s.ok() || seq_used != kMaxSequenceNumber);
if (!s.ok()) {
return s;
}
if (do_one_write) {
for (const auto& seq : unprep_seqs_) {
wpt_db_->RemovePrepared(seq.first, seq.second);
}
unprep_seqs_.clear();
flushed_save_points_.reset(nullptr);
unflushed_save_points_.reset(nullptr);
return s;
} // else do the 2nd write for commit
uint64_t& prepare_seq = seq_used;
ROCKS_LOG_DETAILS(db_impl_->immutable_db_options().info_log,
"RollbackInternal 2nd write prepare_seq: %" PRIu64,
prepare_seq);
// Commit the batch by writing an empty batch to the queue that will release
// the commit sequence number to readers.
WritePrepared: fix two versions in compaction see different status for released snapshots (#4890) Summary: Fix how CompactionIterator::findEarliestVisibleSnapshots handles released snapshot. It fixing the two scenarios: Scenario 1: key1 has two values v1 and v2. There're two snapshots s1 and s2 taken after v1 and v2 are committed. Right after compaction output v2, s1 is released. Now findEarliestVisibleSnapshot may see s1 being released, and return the next snapshot, which is s2. That's larger than v2's earliest visible snapshot, which was s1. The fix: the only place we check against last snapshot and current key snapshot is when we decide whether to compact out a value if it is hidden by a later value. In the check if we see current snapshot is even larger than last snapshot, we know last snapshot is released, and we are safe to compact out current key. Scenario 2: key1 has two values v1 and v2. there are two snapshots s1 and s2 taken after v1 and v2 are committed. During compaction before we process the key, s1 is released. When compaction process v2, snapshot checker may return kSnapshotReleased, and the earliest visible snapshot for v2 become s2. When compaction process v1, snapshot checker may return kIsInSnapshot (for WritePrepared transaction, it could be because v1 is still in commit cache). The result will become inconsistent here. The fix: remember the set of released snapshots ever reported by snapshot checker, and ignore them when finding result for findEarliestVisibleSnapshot. Pull Request resolved: https://github.com/facebook/rocksdb/pull/4890 Differential Revision: D13705538 Pulled By: maysamyabandeh fbshipit-source-id: e577f0d9ee1ff5a6035f26859e56902ecc85a5a4
6 years ago
WriteUnpreparedRollbackPreReleaseCallback update_commit_map_with_prepare(
wpt_db_, db_impl_, unprep_seqs_, prepare_seq);
WriteBatch empty_batch;
empty_batch.PutLogData(Slice());
// In the absence of Prepare markers, use Noop as a batch separator
WriteBatchInternal::InsertNoop(&empty_batch);
s = db_impl_->WriteImpl(write_options_, &empty_batch, nullptr, nullptr,
NO_REF_LOG, DISABLE_MEMTABLE, &seq_used, ONE_BATCH,
&update_commit_map_with_prepare);
assert(!s.ok() || seq_used != kMaxSequenceNumber);
// Mark the txn as rolled back
if (s.ok()) {
for (const auto& seq : unprep_seqs_) {
wpt_db_->RemovePrepared(seq.first, seq.second);
}
}
unprep_seqs_.clear();
flushed_save_points_.reset(nullptr);
unflushed_save_points_.reset(nullptr);
return s;
}
void WriteUnpreparedTxn::Clear() {
if (!recovered_txn_) {
txn_db_impl_->UnLock(this, &GetTrackedKeys());
}
unprep_seqs_.clear();
flushed_save_points_.reset(nullptr);
unflushed_save_points_.reset(nullptr);
recovered_txn_ = false;
largest_validated_seq_ = 0;
assert(active_iterators_.empty());
active_iterators_.clear();
untracked_keys_.clear();
TransactionBaseImpl::Clear();
}
void WriteUnpreparedTxn::SetSavePoint() {
assert((unflushed_save_points_ ? unflushed_save_points_->size() : 0) +
(flushed_save_points_ ? flushed_save_points_->size() : 0) ==
(save_points_ ? save_points_->size() : 0));
PessimisticTransaction::SetSavePoint();
if (unflushed_save_points_ == nullptr) {
unflushed_save_points_.reset(new autovector<size_t>());
}
unflushed_save_points_->push_back(write_batch_.GetDataSize());
}
Status WriteUnpreparedTxn::RollbackToSavePoint() {
assert((unflushed_save_points_ ? unflushed_save_points_->size() : 0) +
(flushed_save_points_ ? flushed_save_points_->size() : 0) ==
(save_points_ ? save_points_->size() : 0));
if (unflushed_save_points_ != nullptr && unflushed_save_points_->size() > 0) {
Status s = PessimisticTransaction::RollbackToSavePoint();
assert(!s.IsNotFound());
unflushed_save_points_->pop_back();
return s;
}
if (flushed_save_points_ != nullptr && !flushed_save_points_->empty()) {
return RollbackToSavePointInternal();
}
return Status::NotFound();
}
Status WriteUnpreparedTxn::RollbackToSavePointInternal() {
Status s;
const bool kClear = true;
TransactionBaseImpl::InitWriteBatch(kClear);
assert(flushed_save_points_->size() > 0);
WriteUnpreparedTxn::SavePoint& top = flushed_save_points_->back();
assert(save_points_ != nullptr && save_points_->size() > 0);
const TransactionKeyMap& tracked_keys = save_points_->top().new_keys_;
ReadOptions roptions;
roptions.snapshot = top.snapshot_->snapshot();
SequenceNumber min_uncommitted =
static_cast_with_check<const SnapshotImpl, const Snapshot>(
roptions.snapshot)
->min_uncommitted_;
SequenceNumber snap_seq = roptions.snapshot->GetSequenceNumber();
WriteUnpreparedTxnReadCallback callback(wupt_db_, snap_seq, min_uncommitted,
top.unprep_seqs_,
kBackedByDBSnapshot);
WriteRollbackKeys(tracked_keys, &write_batch_, &callback, roptions);
const bool kPrepared = true;
s = FlushWriteBatchToDBInternal(!kPrepared);
assert(s.ok());
if (!s.ok()) {
return s;
}
// PessimisticTransaction::RollbackToSavePoint will call also call
// RollbackToSavepoint on write_batch_. However, write_batch_ is empty and has
// no savepoints because this savepoint has already been flushed. Work around
// this by setting a fake savepoint.
write_batch_.SetSavePoint();
s = PessimisticTransaction::RollbackToSavePoint();
assert(s.ok());
if (!s.ok()) {
return s;
}
flushed_save_points_->pop_back();
return s;
}
Status WriteUnpreparedTxn::PopSavePoint() {
assert((unflushed_save_points_ ? unflushed_save_points_->size() : 0) +
(flushed_save_points_ ? flushed_save_points_->size() : 0) ==
(save_points_ ? save_points_->size() : 0));
if (unflushed_save_points_ != nullptr && unflushed_save_points_->size() > 0) {
Status s = PessimisticTransaction::PopSavePoint();
assert(!s.IsNotFound());
unflushed_save_points_->pop_back();
return s;
}
if (flushed_save_points_ != nullptr && !flushed_save_points_->empty()) {
// PessimisticTransaction::PopSavePoint will call also call PopSavePoint on
// write_batch_. However, write_batch_ is empty and has no savepoints
// because this savepoint has already been flushed. Work around this by
// setting a fake savepoint.
write_batch_.SetSavePoint();
Status s = PessimisticTransaction::PopSavePoint();
assert(!s.IsNotFound());
flushed_save_points_->pop_back();
return s;
}
return Status::NotFound();
}
void WriteUnpreparedTxn::MultiGet(const ReadOptions& options,
ColumnFamilyHandle* column_family,
const size_t num_keys, const Slice* keys,
PinnableSlice* values, Status* statuses,
const bool sorted_input) {
SequenceNumber min_uncommitted, snap_seq;
const SnapshotBackup backed_by_snapshot =
wupt_db_->AssignMinMaxSeqs(options.snapshot, &min_uncommitted, &snap_seq);
WriteUnpreparedTxnReadCallback callback(wupt_db_, snap_seq, min_uncommitted,
unprep_seqs_, backed_by_snapshot);
write_batch_.MultiGetFromBatchAndDB(db_, options, column_family, num_keys,
keys, values, statuses, sorted_input,
&callback);
if (UNLIKELY(!callback.valid() ||
!wupt_db_->ValidateSnapshot(snap_seq, backed_by_snapshot))) {
wupt_db_->WPRecordTick(TXN_GET_TRY_AGAIN);
for (size_t i = 0; i < num_keys; i++) {
statuses[i] = Status::TryAgain();
}
}
}
Status WriteUnpreparedTxn::Get(const ReadOptions& options,
ColumnFamilyHandle* column_family,
const Slice& key, PinnableSlice* value) {
SequenceNumber min_uncommitted, snap_seq;
const SnapshotBackup backed_by_snapshot =
wupt_db_->AssignMinMaxSeqs(options.snapshot, &min_uncommitted, &snap_seq);
WriteUnpreparedTxnReadCallback callback(wupt_db_, snap_seq, min_uncommitted,
unprep_seqs_, backed_by_snapshot);
auto res = write_batch_.GetFromBatchAndDB(db_, options, column_family, key,
value, &callback);
if (LIKELY(callback.valid() &&
wupt_db_->ValidateSnapshot(snap_seq, backed_by_snapshot))) {
return res;
} else {
wupt_db_->WPRecordTick(TXN_GET_TRY_AGAIN);
return Status::TryAgain();
}
}
namespace {
static void CleanupWriteUnpreparedWBWIIterator(void* arg1, void* arg2) {
auto txn = reinterpret_cast<WriteUnpreparedTxn*>(arg1);
auto iter = reinterpret_cast<Iterator*>(arg2);
txn->RemoveActiveIterator(iter);
}
} // anonymous namespace
Iterator* WriteUnpreparedTxn::GetIterator(const ReadOptions& options) {
return GetIterator(options, wupt_db_->DefaultColumnFamily());
}
Iterator* WriteUnpreparedTxn::GetIterator(const ReadOptions& options,
ColumnFamilyHandle* column_family) {
// Make sure to get iterator from WriteUnprepareTxnDB, not the root db.
Iterator* db_iter = wupt_db_->NewIterator(options, column_family, this);
assert(db_iter);
auto iter = write_batch_.NewIteratorWithBase(column_family, db_iter);
active_iterators_.push_back(iter);
iter->RegisterCleanup(CleanupWriteUnpreparedWBWIIterator, this, iter);
return iter;
}
Status WriteUnpreparedTxn::ValidateSnapshot(ColumnFamilyHandle* column_family,
const Slice& key,
SequenceNumber* tracked_at_seq) {
// TODO(lth): Reduce duplicate code with WritePrepared ValidateSnapshot logic.
assert(snapshot_);
SequenceNumber min_uncommitted =
static_cast_with_check<const SnapshotImpl, const Snapshot>(
snapshot_.get())
->min_uncommitted_;
SequenceNumber snap_seq = snapshot_->GetSequenceNumber();
// tracked_at_seq is either max or the last snapshot with which this key was
// trackeed so there is no need to apply the IsInSnapshot to this comparison
// here as tracked_at_seq is not a prepare seq.
if (*tracked_at_seq <= snap_seq) {
// If the key has been previous validated at a sequence number earlier
// than the curent snapshot's sequence number, we already know it has not
// been modified.
return Status::OK();
}
*tracked_at_seq = snap_seq;
ColumnFamilyHandle* cfh =
column_family ? column_family : db_impl_->DefaultColumnFamily();
WriteUnpreparedTxnReadCallback snap_checker(
wupt_db_, snap_seq, min_uncommitted, unprep_seqs_, kBackedByDBSnapshot);
return TransactionUtil::CheckKeyForConflicts(db_impl_, cfh, key.ToString(),
snap_seq, false /* cache_only */,
&snap_checker, min_uncommitted);
}
const std::map<SequenceNumber, size_t>&
WriteUnpreparedTxn::GetUnpreparedSequenceNumbers() {
return unprep_seqs_;
}
} // namespace rocksdb
#endif // ROCKSDB_LITE