Some code cleanup (#9003)

Summary:
Pull Request resolved: https://github.com/facebook/rocksdb/pull/9003

cleanup some code before real work.

Reviewed By: ltamasi

Differential Revision: D31525563

fbshipit-source-id: 44558b3594f2200adc7d8621b08b06c77e358a27

utilities/transactions/pessimistic_transaction.h

@@ -44,7 +44,7 @@ class PessimisticTransaction : public TransactionBaseImpl {
   PessimisticTransaction(const PessimisticTransaction&) = delete;
   void operator=(const PessimisticTransaction&) = delete;
 
-  virtual ~PessimisticTransaction();
+  ~PessimisticTransaction() override;
 
   void Reinitialize(TransactionDB* txn_db, const WriteOptions& write_options,
                     const TransactionOptions& txn_options);
@@ -213,7 +213,7 @@ class WriteCommittedTxn : public PessimisticTransaction {
   WriteCommittedTxn(const WriteCommittedTxn&) = delete;
   void operator=(const WriteCommittedTxn&) = delete;
 
-  virtual ~WriteCommittedTxn() {}
+  ~WriteCommittedTxn() override {}
 
  private:
   Status PrepareInternal() override;

utilities/transactions/transaction_base.h

@@ -31,7 +31,7 @@ class TransactionBaseImpl : public Transaction {
   TransactionBaseImpl(DB* db, const WriteOptions& write_options,
                       const LockTrackerFactory& lock_tracker_factory);
 
-  virtual ~TransactionBaseImpl();
+  ~TransactionBaseImpl() override;
 
   // Remove pending operations queued in this transaction.
   virtual void Clear();

utilities/write_batch_with_index/write_batch_with_index_internal.cc

@@ -517,7 +517,7 @@ Status ReadableWriteBatch::GetEntryFromDataOffset(size_t data_offset,
 // 1. first compare the column family, the one with larger CF will be larger;
 // 2. Inside the same CF, we first decode the entry to find the key of the entry
 //    and the entry with larger key will be larger;
-// 3. If two entries are of the same CF and offset, the one with larger offset
+// 3. If two entries are of the same CF and key, the one with larger offset
 //    will be larger.
 // Some times either `entry1` or `entry2` is dummy entry, which is actually
 // a search key. In this case, in step 2, we don't go ahead and decode the