// 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_prepared_txn.h"
#include <cinttypes>
#include <map>
#include <set>
#include "db/column_family.h"
#include "db/db_impl/db_impl.h"
#include "rocksdb/db.h"
#include "rocksdb/status.h"
#include "rocksdb/utilities/transaction_db.h"
#include "util/cast_util.h"
#include "utilities/transactions/pessimistic_transaction.h"
#include "utilities/transactions/write_prepared_txn_db.h"
namespace ROCKSDB_NAMESPACE {
struct WriteOptions;
WritePreparedTxn::WritePreparedTxn(WritePreparedTxnDB* txn_db,
const WriteOptions& write_options,
const TransactionOptions& txn_options)
: PessimisticTransaction(txn_db, write_options, txn_options, false),
wpt_db_(txn_db) {
// Call Initialize outside PessimisticTransaction constructor otherwise it
// would skip overridden functions in WritePreparedTxn since they are not
// defined yet in the constructor of PessimisticTransaction
Initialize(txn_options);
}
void WritePreparedTxn::Initialize(const TransactionOptions& txn_options) {
PessimisticTransaction::Initialize(txn_options);
prepare_batch_cnt_ = 0;
}
void WritePreparedTxn::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 =
wpt_db_->AssignMinMaxSeqs(options.snapshot, &min_uncommitted, &snap_seq);
WritePreparedTxnReadCallback callback(wpt_db_, snap_seq, min_uncommitted,
backed_by_snapshot);
write_batch_.MultiGetFromBatchAndDB(db_, options, column_family, num_keys,
keys, values, statuses, sorted_input,
&callback);
if (UNLIKELY(!callback.valid() ||
!wpt_db_->ValidateSnapshot(snap_seq, backed_by_snapshot))) {
wpt_db_->WPRecordTick(TXN_GET_TRY_AGAIN);
for (size_t i = 0; i < num_keys; i++) {
statuses[i] = Status::TryAgain();
}
}
}
Status WritePreparedTxn::Get(const ReadOptions& options,
ColumnFamilyHandle* column_family,
const Slice& key, PinnableSlice* pinnable_val) {
SequenceNumber min_uncommitted, snap_seq;
const SnapshotBackup backed_by_snapshot =
wpt_db_->AssignMinMaxSeqs(options.snapshot, &min_uncommitted, &snap_seq);
WritePreparedTxnReadCallback callback(wpt_db_, snap_seq, min_uncommitted,
backed_by_snapshot);
Status res = write_batch_.GetFromBatchAndDB(db_, options, column_family, key,
pinnable_val, &callback);
const bool callback_valid =
callback.valid(); // NOTE: validity of callback must always be checked
// before it is destructed
if (res.ok()) {
if (!LIKELY(callback_valid &&
wpt_db_->ValidateSnapshot(callback.max_visible_seq(),
backed_by_snapshot))) {
wpt_db_->WPRecordTick(TXN_GET_TRY_AGAIN);
res = Status::TryAgain();
}
}
return res;
}
Iterator* WritePreparedTxn::GetIterator(const ReadOptions& options) {
// Make sure to get iterator from WritePrepareTxnDB, not the root db.
Iterator* db_iter = wpt_db_->NewIterator(options);
assert(db_iter);
return write_batch_.NewIteratorWithBase(db_iter);
}
Iterator* WritePreparedTxn::GetIterator(const ReadOptions& options,
ColumnFamilyHandle* column_family) {
// Make sure to get iterator from WritePrepareTxnDB, not the root db.
Iterator* db_iter = wpt_db_->NewIterator(options, column_family);
assert(db_iter);
return write_batch_.NewIteratorWithBase(column_family, db_iter);
}
Status WritePreparedTxn::PrepareInternal() {
WriteOptions write_options = write_options_;
write_options.disableWAL = false;
const bool WRITE_AFTER_COMMIT = true;
const bool kFirstPrepareBatch = true;
auto s = WriteBatchInternal::MarkEndPrepare(GetWriteBatch()->GetWriteBatch(),
name_, !WRITE_AFTER_COMMIT);
assert(s.ok());
// For each duplicate key we account for a new sub-batch
prepare_batch_cnt_ = GetWriteBatch()->SubBatchCnt();
// Having AddPrepared 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, kFirstPrepareBatch);
const bool DISABLE_MEMTABLE = true;
uint64_t seq_used = kMaxSequenceNumber;
s = db_impl_->WriteImpl(write_options, GetWriteBatch()->GetWriteBatch(),
/*callback*/ nullptr, &log_number_, /*log ref*/ 0,
!DISABLE_MEMTABLE, &seq_used, prepare_batch_cnt_,
&add_prepared_callback);
assert(!s.ok() || seq_used != kMaxSequenceNumber);
auto prepare_seq = seq_used;
SetId(prepare_seq);
return s;
}
Status WritePreparedTxn::CommitWithoutPrepareInternal() {
// For each duplicate key we account for a new sub-batch
const size_t batch_cnt = GetWriteBatch()->SubBatchCnt();
return CommitBatchInternal(GetWriteBatch()->GetWriteBatch(), batch_cnt);
}
Status WritePreparedTxn::CommitBatchInternal(WriteBatch* batch,
size_t batch_cnt) {
return wpt_db_->WriteInternal(write_options_, batch, batch_cnt, this);
}
Status WritePreparedTxn::CommitInternal() {
ROCKS_LOG_DETAILS(db_impl_->immutable_db_options().info_log,
"CommitInternal prepare_seq: %" PRIu64, GetID());
// 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;
auto s = WriteBatchInternal::MarkCommit(working_batch, name_);
assert(s.ok());
const bool for_recovery = use_only_the_last_commit_time_batch_for_recovery_;
if (!empty) {
// 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
if (for_recovery) {
WriteBatchInternal::SetAsLatestPersistentState(working_batch);
} else {
return Status::InvalidArgument(
"Commit-time-batch can only be used if "
"use_only_the_last_commit_time_batch_for_recovery is true");
}
}
auto prepare_seq = GetId();
const bool includes_data = !empty && !for_recovery;
assert(prepare_batch_cnt_);
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());
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;
WritePreparedCommitEntryPreReleaseCallback update_commit_map(
wpt_db_, db_impl_, prepare_seq, prepare_batch_cnt_, commit_batch_cnt);
// This is to call AddPrepared on CommitTimeWriteBatch
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;
// If `two_write_queues && includes_data`, then `do_one_write` is false. The
// following `WriteImpl` will insert the data of the commit-time-batch into
// the database before updating the commit cache. Therefore, the data of the
// commmit-time-batch is considered uncommitted. Furthermore, since data of
// the commit-time-batch are not locked, it is possible for two uncommitted
// versions of the same key to co-exist for a (short) period of time until
// the commit cache is updated by the second write. If the two uncommitted
// keys are compacted to the bottommost level in the meantime, it is possible
// that compaction iterator will zero out the sequence numbers of both, thus
// violating the invariant that an SST does not have two identical internal
// keys. To prevent this situation, we should allow the usage of
// commit-time-batch only if the user sets
// TransactionOptions::use_only_the_last_commit_time_batch_for_recovery to
// true. See the comments about GetCommitTimeWriteBatch() in
// include/rocksdb/utilities/transaction.h.
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 (UNLIKELY(!db_impl_->immutable_db_options().two_write_queues &&
s.ok())) {
// Note: RemovePrepared should be called after WriteImpl that publishsed
// the seq. Otherwise SmallestUnCommittedSeq optimization breaks.
wpt_db_->RemovePrepared(prepare_seq, prepare_batch_cnt_);
} // else RemovePrepared is called from within PreReleaseCallback
if (UNLIKELY(!do_one_write)) {
assert(!s.ok());
// Cleanup the prepared entry we added with add_prepared_callback
wpt_db_->RemovePrepared(commit_batch_seq, commit_batch_cnt);
}
return s;
} // else do the 2nd write to publish seq
// 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.
const size_t kZeroData = 0;
// Update commit map only from the 2nd queue
WritePreparedCommitEntryPreReleaseCallback update_commit_map_with_aux_batch(
wpt_db_, db_impl_, prepare_seq, prepare_batch_cnt_, kZeroData,
commit_batch_seq, commit_batch_cnt);
WriteBatch empty_batch;
s = empty_batch.PutLogData(Slice());
assert(s.ok());
// In the absence of Prepare markers, use Noop as a batch separator
s = WriteBatchInternal::InsertNoop(&empty_batch);
assert(s.ok());
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_with_aux_batch);
assert(!s.ok() || seq_used != kMaxSequenceNumber);
return s;
}
Status WritePreparedTxn::RollbackInternal() {
ROCKS_LOG_WARN(db_impl_->immutable_db_options().info_log,
"RollbackInternal prepare_seq: %" PRIu64, GetId());
assert(db_impl_);
assert(wpt_db_);
WriteBatch rollback_batch(0 /* reserved_bytes */, 0 /* max_bytes */,
write_options_.protection_bytes_per_key,
0 /* default_cf_ts_sz */);
assert(GetId() != kMaxSequenceNumber);
assert(GetId() > 0);
auto cf_map_shared_ptr = wpt_db_->GetCFHandleMap();
auto cf_comp_map_shared_ptr = wpt_db_->GetCFComparatorMap();
auto read_at_seq = kMaxSequenceNumber;
ReadOptions roptions;
// to prevent callback's seq to be overrriden inside DBImpk::Get
roptions.snapshot = wpt_db_->GetMaxSnapshot();
struct RollbackWriteBatchBuilder : public WriteBatch::Handler {
DBImpl* const db_;
WritePreparedTxnDB* const wpt_db_;
WritePreparedTxnReadCallback callback_;
WriteBatch* rollback_batch_;
std::map<uint32_t, const Comparator*>& comparators_;
std::map<uint32_t, ColumnFamilyHandle*>& handles_;
using CFKeys = std::set<Slice, SetComparator>;
std::map<uint32_t, CFKeys> keys_;
bool rollback_merge_operands_;
ReadOptions roptions_;
RollbackWriteBatchBuilder(
DBImpl* db, WritePreparedTxnDB* wpt_db, SequenceNumber snap_seq,
WriteBatch* dst_batch,
std::map<uint32_t, const Comparator*>& comparators,
std::map<uint32_t, ColumnFamilyHandle*>& handles,
bool rollback_merge_operands, const ReadOptions& _roptions)
: db_(db),
wpt_db_(wpt_db),
callback_(wpt_db, snap_seq), // disable min_uncommitted optimization
rollback_batch_(dst_batch),
comparators_(comparators),
handles_(handles),
rollback_merge_operands_(rollback_merge_operands),
roptions_(_roptions) {}
Status Rollback(uint32_t cf, const Slice& key) {
Status s;
CFKeys& cf_keys = keys_[cf];
if (cf_keys.size() == 0) { // just inserted
auto cmp = comparators_[cf];
keys_[cf] = CFKeys(SetComparator(cmp));
}
auto it = cf_keys.insert(key);
// second is false if a element already existed.
if (it.second == false) {
return s;
}
PinnableSlice pinnable_val;
bool not_used;
auto cf_handle = handles_[cf];
DBImpl::GetImplOptions get_impl_options;
get_impl_options.column_family = cf_handle;
get_impl_options.value = &pinnable_val;
get_impl_options.value_found = ¬_used;
get_impl_options.callback = &callback_;
s = db_->GetImpl(roptions_, key, get_impl_options);
assert(s.ok() || s.IsNotFound());
if (s.ok()) {
s = rollback_batch_->Put(cf_handle, key, pinnable_val);
assert(s.ok());
} else if (s.IsNotFound()) {
// There has been no readable value before txn. By adding a delete we
// make sure that there will be none afterwards either.
if (wpt_db_->ShouldRollbackWithSingleDelete(cf_handle, key)) {
s = rollback_batch_->SingleDelete(cf_handle, key);
} else {
s = rollback_batch_->Delete(cf_handle, key);
}
assert(s.ok());
} else {
// Unexpected status. Return it to the user.
}
return s;
}
Status PutCF(uint32_t cf, const Slice& key, const Slice& /*val*/) override {
return Rollback(cf, key);
}
Status DeleteCF(uint32_t cf, const Slice& key) override {
return Rollback(cf, key);
}
Status SingleDeleteCF(uint32_t cf, const Slice& key) override {
return Rollback(cf, key);
}
Status MergeCF(uint32_t cf, const Slice& key,
const Slice& /*val*/) override {
if (rollback_merge_operands_) {
return Rollback(cf, key);
} else {
return Status::OK();
}
}
Status MarkNoop(bool) override { return Status::OK(); }
Status MarkBeginPrepare(bool) override { return Status::OK(); }
Status MarkEndPrepare(const Slice&) override { return Status::OK(); }
Status MarkCommit(const Slice&) override { return Status::OK(); }
Status MarkRollback(const Slice&) override {
return Status::InvalidArgument();
}
protected:
Handler::OptionState WriteAfterCommit() const override {
return Handler::OptionState::kDisabled;
}
} rollback_handler(db_impl_, wpt_db_, read_at_seq, &rollback_batch,
*cf_comp_map_shared_ptr.get(), *cf_map_shared_ptr.get(),
wpt_db_->txn_db_options_.rollback_merge_operands,
roptions);
auto s = GetWriteBatch()->GetWriteBatch()->Iterate(&rollback_handler);
if (!s.ok()) {
return s;
}
// The Rollback marker will be used as a batch separator
s = WriteBatchInternal::MarkRollback(&rollback_batch, name_);
assert(s.ok());
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;
const size_t ONE_BATCH = 1;
const bool kFirstPrepareBatch = true;
// 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_.
AddPreparedCallback add_prepared_callback(
wpt_db_, db_impl_, ONE_BATCH,
db_impl_->immutable_db_options().two_write_queues, !kFirstPrepareBatch);
WritePreparedCommitEntryPreReleaseCallback update_commit_map(
wpt_db_, db_impl_, GetId(), prepare_batch_cnt_, ONE_BATCH);
PreReleaseCallback* pre_release_callback;
if (do_one_write) {
pre_release_callback = &update_commit_map;
} else {
pre_release_callback = &add_prepared_callback;
}
// 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 rollback batch commits with PreReleaseCallback.
s = db_impl_->WriteImpl(write_options_, &rollback_batch, nullptr, nullptr,
NO_REF_LOG, !DISABLE_MEMTABLE, &seq_used, ONE_BATCH,
pre_release_callback);
assert(!s.ok() || seq_used != kMaxSequenceNumber);
if (!s.ok()) {
return s;
}
if (do_one_write) {
assert(!db_impl_->immutable_db_options().two_write_queues);
wpt_db_->RemovePrepared(GetId(), prepare_batch_cnt_);
return s;
} // else do the 2nd write for commit
uint64_t rollback_seq = seq_used;
ROCKS_LOG_DETAILS(db_impl_->immutable_db_options().info_log,
"RollbackInternal 2nd write rollback_seq: %" PRIu64,
rollback_seq);
// Commit the batch by writing an empty batch to the queue that will release
// the commit sequence number to readers.
WritePreparedRollbackPreReleaseCallback update_commit_map_with_prepare(
wpt_db_, db_impl_, GetId(), rollback_seq, prepare_batch_cnt_);
WriteBatch empty_batch;
s = empty_batch.PutLogData(Slice());
assert(s.ok());
// In the absence of Prepare markers, use Noop as a batch separator
s = WriteBatchInternal::InsertNoop(&empty_batch);
assert(s.ok());
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);
ROCKS_LOG_DETAILS(db_impl_->immutable_db_options().info_log,
"RollbackInternal (status=%s) commit: %" PRIu64,
s.ToString().c_str(), GetId());
// TODO(lth): For WriteUnPrepared that rollback is called frequently,
// RemovePrepared could be moved to the callback to reduce lock contention.
if (s.ok()) {
wpt_db_->RemovePrepared(GetId(), prepare_batch_cnt_);
}
// Note: RemovePrepared for prepared batch is called from within
// PreReleaseCallback
wpt_db_->RemovePrepared(rollback_seq, ONE_BATCH);
return s;
}
Status WritePreparedTxn::ValidateSnapshot(ColumnFamilyHandle* column_family,
const Slice& key,
SequenceNumber* tracked_at_seq) {
assert(snapshot_);
SequenceNumber min_uncommitted =
static_cast_with_check<const SnapshotImpl>(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();
WritePreparedTxnReadCallback snap_checker(wpt_db_, snap_seq, min_uncommitted,
kBackedByDBSnapshot);
// TODO(yanqin): support user-defined timestamp
return TransactionUtil::CheckKeyForConflicts(
db_impl_, cfh, key.ToString(), snap_seq, /*ts=*/nullptr,
false /* cache_only */, &snap_checker, min_uncommitted);
}
void WritePreparedTxn::SetSnapshot() {
const bool kForWWConflictCheck = true;
SnapshotImpl* snapshot = wpt_db_->GetSnapshotInternal(kForWWConflictCheck);
SetSnapshotInternal(snapshot);
}
Status WritePreparedTxn::RebuildFromWriteBatch(WriteBatch* src_batch) {
auto ret = PessimisticTransaction::RebuildFromWriteBatch(src_batch);
prepare_batch_cnt_ = GetWriteBatch()->SubBatchCnt();
return ret;
}
} // namespace ROCKSDB_NAMESPACE
#endif // ROCKSDB_LITE