Turn Transaction into a pure interface class

include/rocksdb/utilities/transaction.h

@@ -139,7 +139,7 @@ class Transaction {
   Transaction(const Transaction&) = delete;
   void operator=(const Transaction&) = delete;
 
-  virtual ~Transaction() {}
+  virtual ~Transaction() = default;
 
   // If a transaction has a snapshot set, the transaction will ensure that
   // any keys successfully written(or fetched via GetForUpdate()) have not
@@ -699,13 +699,13 @@ class Transaction {
   // output SST file to have two identical internal keys.
   virtual WriteBatch* GetCommitTimeWriteBatch() = 0;
 
-  virtual void SetLogNumber(uint64_t log) { log_number_ = log; }
+  virtual void SetLogNumber(uint64_t log) = 0;
 
-  virtual uint64_t GetLogNumber() const { return log_number_; }
+  virtual uint64_t GetLogNumber() const = 0;
 
   virtual Status SetName(const TransactionName& name) = 0;
 
-  virtual TransactionName GetName() const { return name_; }
+  virtual TransactionName GetName() const = 0;
 
   virtual TransactionID GetID() const { return 0; }
 
@@ -729,16 +729,16 @@ class Transaction {
     LOCKS_STOLEN = 7,
   };
 
-  TransactionState GetState() const { return txn_state_; }
-  void SetState(TransactionState state) { txn_state_ = state; }
+  virtual TransactionState GetState() const = 0;
+  virtual void SetState(TransactionState state) = 0;
 
   // NOTE: Experimental feature
   // The globally unique id with which the transaction is identified. This id
   // might or might not be set depending on the implementation. Similarly the
   // implementation decides the point in lifetime of a transaction at which it
   // assigns the id. Although currently it is the case, the id is not guaranteed
   // to remain the same across restarts.
-  uint64_t GetId() { return id_; }
+  virtual uint64_t GetId() = 0;
 
   virtual Status SetReadTimestampForValidation(TxnTimestamp /*ts*/) {
     return Status::NotSupported("timestamp not supported");
@@ -751,22 +751,11 @@ class Transaction {
   virtual TxnTimestamp GetCommitTimestamp() const { return kMaxTxnTimestamp; }
 
  protected:
-  explicit Transaction(const TransactionDB* /*db*/) {}
-  Transaction() : log_number_(0), txn_state_(STARTED) {}
+  Transaction() = default;
 
-  // the log in which the prepared section for this txn resides
-  // (for two phase commit)
-  uint64_t log_number_;
-  TransactionName name_;
+  virtual void SetId(uint64_t id) = 0;
 
-  // Execution status of the transaction.
-  std::atomic<TransactionState> txn_state_;
-
-  uint64_t id_ = 0;
-  virtual void SetId(uint64_t id) {
-    assert(id_ == 0);
-    id_ = id;
-  }
+  virtual uint64_t GetLastLogNumber() const = 0;
 
   virtual Status GetImpl(const ReadOptions& /* options */,
                          ColumnFamilyHandle* /* column_family */,
@@ -783,8 +772,6 @@ class Transaction {
     return s;
   }
 
-  virtual uint64_t GetLastLogNumber() const { return log_number_; }
-
  private:
   friend class PessimisticTransactionDB;
   friend class WriteUnpreparedTxnDB;

unreleased_history/public_api_changes/transaction_interface.md

@@ -0,0 +1 @@
+The `Transaction` class is now an abstract interface class with no data members, and the methods `Transaction::{SetLogNumber, GetLogNumber, GetName, GetState, SetState, GetId, SetId, GetLastLogNumber}` are now accordingly pure virtuals implemented further down in the class hierarchy.

utilities/transactions/transaction_base.cc

@@ -74,7 +74,6 @@ TransactionBaseImpl::TransactionBaseImpl(
                          0 /* default_cf_ts_sz */),
       indexing_enabled_(true) {
   assert(dynamic_cast<DBImpl*>(db_) != nullptr);
-  log_number_ = 0;
   if (dbimpl_->allow_2pc()) {
     InitWriteBatch();
   }

utilities/transactions/transaction_base.h

@@ -309,9 +309,27 @@ class TransactionBaseImpl : public Transaction {
 
   WriteBatch* GetCommitTimeWriteBatch() override;
 
+  void SetLogNumber(uint64_t log) override { log_number_ = log; }
+
+  uint64_t GetLogNumber() const override { return log_number_; }
+
+  TransactionName GetName() const override { return name_; }
+
+  TransactionState GetState() const override { return txn_state_; }
+  void SetState(TransactionState state) override { txn_state_ = state; }
+
+  uint64_t GetId() override { return id_; }
+
   LockTracker& GetTrackedLocks() { return *tracked_locks_; }
 
  protected:
+  void SetId(uint64_t id) override {
+    assert(id_ == 0);
+    id_ = id;
+  }
+
+  uint64_t GetLastLogNumber() const override { return log_number_; }
+
   template <typename IterType, typename ImplType,
             typename ErrorIteratorFuncType>
   std::unique_ptr<IterType> NewMultiCfIterator(
@@ -380,6 +398,17 @@ class TransactionBaseImpl : public Transaction {
 
   const LockTrackerFactory& lock_tracker_factory_;
 
+  // the log in which the prepared section for this txn resides
+  // (for two phase commit)
+  uint64_t log_number_ = 0;
+
+  TransactionName name_;
+
+  // Execution status of the transaction.
+  std::atomic<TransactionState> txn_state_{STARTED};
+
+  uint64_t id_ = 0;
+
   // Stores that time the txn was constructed, in microseconds.
   uint64_t start_time_;
 

utilities/transactions/write_prepared_txn.h

@@ -84,7 +84,7 @@ class WritePreparedTxn : public PessimisticTransaction {
   void Initialize(const TransactionOptions& txn_options) override;
   // Override the protected SetId to make it visible to the friend class
   // WritePreparedTxnDB
-  inline void SetId(uint64_t id) override { Transaction::SetId(id); }
+  void SetId(uint64_t id) override { TransactionBaseImpl::SetId(id); }
 
  private:
   friend class WritePreparedTransactionTest_BasicRecoveryTest_Test;