text: // 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
  
  #ifndef ROCKSDB_LITE
  
  #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_NAMESPACE {
  
  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 {
   public:
    PessimisticTransaction(TransactionDB* db, const WriteOptions& write_options,
                           const TransactionOptions& txn_options,
                           const bool init = true);
    // No copying allowed
    PessimisticTransaction(const PessimisticTransaction&) = delete;
    void operator=(const PessimisticTransaction&) = delete;
  
    ~PessimisticTransaction() override;
  
    void Reinitialize(TransactionDB* txn_db, const WriteOptions& write_options,
                      const TransactionOptions& txn_options);
  
    Status Prepare() override;
  
    Status Commit() override;
  
    // It is basically Commit without going through Prepare phase. The write batch
    // is also directly provided instead of expecting txn to gradually batch the
    // transactions writes to an internal write batch.
    Status CommitBatch(WriteBatch* batch);
  
    Status Rollback() override;
  
    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_txn_ids_.clear();
      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 GetRangeLock(ColumnFamilyHandle* column_family,
                                const Endpoint& start_key,
                                const Endpoint& end_key) override;
  
   protected:
    // Refer to
    // TransactionOptions::use_only_the_last_commit_time_batch_for_recovery
    bool use_only_the_last_commit_time_batch_for_recovery_ = false;
    // Refer to
    // TransactionOptions::skip_prepare
    bool skip_prepare_ = false;
  
    virtual Status PrepareInternal() = 0;
  
    virtual Status CommitWithoutPrepareInternal() = 0;
  
    // batch_cnt if non-zero is the number of sub-batches. A sub-batch is a batch
    // with no duplicate keys. If zero, then the number of sub-batches is unknown.
    virtual Status CommitBatchInternal(WriteBatch* batch,
                                       size_t batch_cnt = 0) = 0;
  
    virtual Status CommitInternal() = 0;
  
    virtual Status RollbackInternal() = 0;
  
    virtual void Initialize(const TransactionOptions& txn_options);
  
    Status LockBatch(WriteBatch* batch, LockTracker* keys_to_unlock);
  
    Status TryLock(ColumnFamilyHandle* column_family, const Slice& key,
                   bool read_only, bool exclusive, const bool do_validate = true,
                   const bool assume_tracked = 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_;
  
   private:
    friend class TransactionTest_ValidateSnapshotTest_Test;
    // 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 PointLockManager::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_;
  
    // Refer to TransactionOptions::skip_concurrency_control
    bool skip_concurrency_control_;
  
    virtual Status ValidateSnapshot(ColumnFamilyHandle* column_family,
                                    const Slice& key,
                                    SequenceNumber* tracked_at_seq);
  
    void UnlockGetForUpdate(ColumnFamilyHandle* column_family,
                            const Slice& key) override;
  };
  
  class WriteCommittedTxn : public PessimisticTransaction {
   public:
    WriteCommittedTxn(TransactionDB* db, const WriteOptions& write_options,
                      const TransactionOptions& txn_options);
    // No copying allowed
    WriteCommittedTxn(const WriteCommittedTxn&) = delete;
    void operator=(const WriteCommittedTxn&) = delete;
  
    ~WriteCommittedTxn() override {}
  
   private:
    Status PrepareInternal() override;
  
    Status CommitWithoutPrepareInternal() override;
  
    Status CommitBatchInternal(WriteBatch* batch, size_t batch_cnt) override;
  
    Status CommitInternal() override;
  
    Status RollbackInternal() override;
  };
  
  }  // namespace ROCKSDB_NAMESPACE
  
  #endif  // ROCKSDB_LITE
  