Small issues (#4564)

Summary:
Couple of very minor improvements (typos in comments, full qualification of class name, reordering members of a struct to make it smaller)
Pull Request resolved: https://github.com/facebook/rocksdb/pull/4564

Differential Revision: D10510183

Pulled By: maysamyabandeh

fbshipit-source-id: c7ddf9bfbf2db08cd31896c3fd93789d3fa68c8b

include/rocksdb/utilities/transaction_db.h

@@ -171,8 +171,8 @@ struct KeyLockInfo {
 struct DeadlockInfo {
   TransactionID m_txn_id;
   uint32_t m_cf_id;
-  std::string m_waiting_key;
   bool m_exclusive;
+  std::string m_waiting_key;
 };
 
 struct DeadlockPath {

memtable/write_buffer_manager.cc

@@ -79,7 +79,7 @@ WriteBufferManager::~WriteBufferManager() {
 void WriteBufferManager::ReserveMemWithCache(size_t mem) {
 #ifndef ROCKSDB_LITE
   assert(cache_rep_ != nullptr);
-  // Use a mutex to protect various data structures. Can be optimzied to a
+  // Use a mutex to protect various data structures. Can be optimized to a
   // lock-free solution if it ends up with a performance bottleneck.
   std::lock_guard<std::mutex> lock(cache_rep_->cache_mutex_);
 
@@ -102,14 +102,14 @@ void WriteBufferManager::ReserveMemWithCache(size_t mem) {
 void WriteBufferManager::FreeMemWithCache(size_t mem) {
 #ifndef ROCKSDB_LITE
   assert(cache_rep_ != nullptr);
-  // Use a mutex to protect various data structures. Can be optimzied to a
+  // Use a mutex to protect various data structures. Can be optimized to a
   // lock-free solution if it ends up with a performance bottleneck.
   std::lock_guard<std::mutex> lock(cache_rep_->cache_mutex_);
   size_t new_mem_used = memory_used_.load(std::memory_order_relaxed) - mem;
   memory_used_.store(new_mem_used, std::memory_order_relaxed);
   // Gradually shrink memory costed in the block cache if the actual
   // usage is less than 3/4 of what we reserve from the block cache.
-  // We do this becausse:
+  // We do this because:
   // 1. we don't pay the cost of the block cache immediately a memtable is
   //    freed, as block cache insert is expensive;
   // 2. eventually, if we walk away from a temporary memtable size increase,

utilities/transactions/transaction_lock_mgr.cc

@@ -104,7 +104,7 @@ void DeadlockInfoBuffer::AddNewPath(DeadlockPath path) {
     return;
   }
 
-  paths_buffer_[buffer_idx_] = path;
+  paths_buffer_[buffer_idx_] = std::move(path);
   buffer_idx_ = (buffer_idx_ + 1) % paths_buffer_.size();
 }
 
@@ -494,8 +494,8 @@ bool TransactionLockMgr::IncrementWaiters(
 
         auto extracted_info = wait_txn_map_.Get(queue_values[head]);
         path.push_back({queue_values[head], extracted_info.m_cf_id,
-                        extracted_info.m_waiting_key,
-                        extracted_info.m_exclusive});
+                        extracted_info.m_exclusive,
+                        extracted_info.m_waiting_key});
         head = queue_parents[head];
       }
       env->GetCurrentTime(&deadlock_time);

utilities/transactions/write_prepared_txn_db.h

@@ -549,7 +549,7 @@ class WritePreparedTxnDB : public PessimisticTransactionDB {
   static const size_t DEF_SNAPSHOT_CACHE_BITS = static_cast<size_t>(7);
   const size_t SNAPSHOT_CACHE_BITS;
   const size_t SNAPSHOT_CACHE_SIZE;
-  unique_ptr<std::atomic<SequenceNumber>[]> snapshot_cache_;
+  std::unique_ptr<std::atomic<SequenceNumber>[]> snapshot_cache_;
   // 2nd list for storing snapshots. The list sorted in ascending order.
   // Thread-safety is provided with snapshots_mutex_.
   std::vector<SequenceNumber> snapshots_;
@@ -567,7 +567,7 @@ class WritePreparedTxnDB : public PessimisticTransactionDB {
   const CommitEntry64bFormat FORMAT;
   // commit_cache_ must be initialized to zero to tell apart an empty index from
   // a filled one. Thread-safety is provided with commit_cache_mutex_.
-  unique_ptr<std::atomic<CommitEntry64b>[]> commit_cache_;
+  std::unique_ptr<std::atomic<CommitEntry64b>[]> commit_cache_;
   // The largest evicted *commit* sequence number from the commit_cache_. If a
   // seq is smaller than max_evicted_seq_ is might or might not be present in
   // commit_cache_. So commit_cache_ must first be checked before consulting