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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).
#pragma once
#include <algorithm>
#include <atomic>
#include <mutex>
#include <stack>
#include <string>
#include <unordered_map>
#include <vector>
#include "db/write_callback.h"
#include "rocksdb/db.h"
#include "rocksdb/slice.h"
#include "rocksdb/snapshot.h"
#include "rocksdb/status.h"
#include "rocksdb/types.h"
#include "rocksdb/utilities/transaction.h"
#include "rocksdb/utilities/transaction_db.h"
#include "rocksdb/utilities/write_batch_with_index.h"
#include "util/autovector.h"
#include "utilities/transactions/transaction_base.h"
#include "utilities/transactions/transaction_util.h"
namespace rocksdb {
class PessimisticTransactionDB;
// A transaction under pessimistic concurrency control. This class implements
// the locking API and interfaces with the lock manager as well as the
// pessimistic transactional db.
class PessimisticTransaction : public TransactionBaseImpl {
PessimisticTransaction(TransactionDB* db, const WriteOptions& write_options,
const TransactionOptions& txn_options);
virtual ~PessimisticTransaction();
void Reinitialize(TransactionDB* txn_db, const WriteOptions& write_options,
const TransactionOptions& txn_options);
Status Prepare() override;
Status Commit() override;
virtual Status CommitBatch(WriteBatch* batch) = 0;
Status Rollback() override = 0;
Status RollbackToSavePoint() override;
Status SetName(const TransactionName& name) override;
// Generate a new unique transaction identifier
static TransactionID GenTxnID();
TransactionID GetID() const override { return txn_id_; }
std::vector<TransactionID> GetWaitingTxns(uint32_t* column_family_id,
std::string* key) const override {
std::lock_guard<std::mutex> lock(wait_mutex_);
std::vector<TransactionID> ids(waiting_txn_ids_.size());
if (key) *key = waiting_key_ ? *waiting_key_ : "";
if (column_family_id) *column_family_id = waiting_cf_id_;
std::copy(waiting_txn_ids_.begin(), waiting_txn_ids_.end(), ids.begin());
return ids;
void SetWaitingTxn(autovector<TransactionID> ids, uint32_t column_family_id,
const std::string* key) {
std::lock_guard<std::mutex> lock(wait_mutex_);
waiting_txn_ids_ = ids;
waiting_cf_id_ = column_family_id;
waiting_key_ = key;
void ClearWaitingTxn() {
std::lock_guard<std::mutex> lock(wait_mutex_);
waiting_cf_id_ = 0;
waiting_key_ = nullptr;
// Returns the time (in microseconds according to Env->GetMicros())
// that this transaction will be expired. Returns 0 if this transaction does
// not expire.
uint64_t GetExpirationTime() const { return expiration_time_; }
// returns true if this transaction has an expiration_time and has expired.
bool IsExpired() const;
// Returns the number of microseconds a transaction can wait on acquiring a
// lock or -1 if there is no timeout.
int64_t GetLockTimeout() const { return lock_timeout_; }
void SetLockTimeout(int64_t timeout) override {
lock_timeout_ = timeout * 1000;
// Returns true if locks were stolen successfully, false otherwise.
bool TryStealingLocks();
bool IsDeadlockDetect() const override { return deadlock_detect_; }
int64_t GetDeadlockDetectDepth() const { return deadlock_detect_depth_; }
virtual Status PrepareInternal() = 0;
virtual Status CommitWithoutPrepareInternal() = 0;
virtual Status CommitInternal() = 0;
void Initialize(const TransactionOptions& txn_options);
Status LockBatch(WriteBatch* batch, TransactionKeyMap* keys_to_unlock);
Status TryLock(ColumnFamilyHandle* column_family, const Slice& key,
bool read_only, bool exclusive,
bool untracked = false) override;
void Clear() override;
PessimisticTransactionDB* txn_db_impl_;
DBImpl* db_impl_;
// If non-zero, this transaction should not be committed after this time (in
// microseconds according to Env->NowMicros())
uint64_t expiration_time_;
// Used to create unique ids for transactions.
static std::atomic<TransactionID> txn_id_counter_;
// Unique ID for this transaction
TransactionID txn_id_;
// IDs for the transactions that are blocking the current transaction.
// empty if current transaction is not waiting.
autovector<TransactionID> waiting_txn_ids_;
// The following two represents the (cf, key) that a transaction is waiting
// on.
// If waiting_key_ is not null, then the pointer should always point to
// a valid string object. The reason is that it is only non-null when the
// transaction is blocked in the TransactionLockMgr::AcquireWithTimeout
// function. At that point, the key string object is one of the function
// parameters.
uint32_t waiting_cf_id_;
const std::string* waiting_key_;
// Mutex protecting waiting_txn_ids_, waiting_cf_id_ and waiting_key_.
mutable std::mutex wait_mutex_;
// Timeout in microseconds when locking a key or -1 if there is no timeout.
int64_t lock_timeout_;
// Whether to perform deadlock detection or not.
bool deadlock_detect_;
// Whether to perform deadlock detection or not.
int64_t deadlock_detect_depth_;
Status ValidateSnapshot(ColumnFamilyHandle* column_family, const Slice& key,
SequenceNumber prev_seqno, SequenceNumber* new_seqno);
void UnlockGetForUpdate(ColumnFamilyHandle* column_family,
const Slice& key) override;
// No copying allowed
PessimisticTransaction(const PessimisticTransaction&);
void operator=(const PessimisticTransaction&);
class WriteCommittedTxn : public PessimisticTransaction {
WriteCommittedTxn(TransactionDB* db, const WriteOptions& write_options,
const TransactionOptions& txn_options);
virtual ~WriteCommittedTxn() {}
Status CommitBatch(WriteBatch* batch) override;
Status Rollback() override;
Status PrepareInternal() override;
Status CommitWithoutPrepareInternal() override;
Status CommitInternal() override;
Status ValidateSnapshot(ColumnFamilyHandle* column_family, const Slice& key,
SequenceNumber prev_seqno, SequenceNumber* new_seqno);
// No copying allowed
WriteCommittedTxn(const WriteCommittedTxn&);
void operator=(const WriteCommittedTxn&);
// Used at commit time to check whether transaction is committing before its
// expiration time.
class TransactionCallback : public WriteCallback {
explicit TransactionCallback(PessimisticTransaction* txn) : txn_(txn) {}
Status Callback(DB* /* unused */) override {
if (txn_->IsExpired()) {
return Status::Expired();
} else {
return Status::OK();
bool AllowWriteBatching() override { return true; }
PessimisticTransaction* txn_;
} // namespace rocksdb
#endif // ROCKSDB_LITE