db_impl_write.cc: use stats_ instead of immutable_db_options_.stats (#9053)

Summary:
This PR has no semantic changes, just to make code shorter.

`stats_` has value same with `immutable_db_options_.stats`.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9053

Reviewed By: zhichao-cao

Differential Revision: D31801603

Pulled By: anand1976

fbshipit-source-id: cbd8fe478d3e90ae078ace49b4f2eb9bb028ccf6

db/db_impl/db_impl_write.cc

@@ -161,8 +161,7 @@ Status DBImpl::WriteImpl(const WriteOptions& write_options,
     RecordTick(stats_, WRITE_WITH_WAL);
   }
 
-  StopWatch write_sw(immutable_db_options_.clock, immutable_db_options_.stats,
-                     DB_WRITE);
+  StopWatch write_sw(immutable_db_options_.clock, stats_, DB_WRITE);
 
   write_thread_.JoinBatchGroup(&w);
   if (w.state == WriteThread::STATE_PARALLEL_MEMTABLE_WRITER) {
@@ -472,8 +471,7 @@ Status DBImpl::PipelinedWriteImpl(const WriteOptions& write_options,
                                   uint64_t* log_used, uint64_t log_ref,
                                   bool disable_memtable, uint64_t* seq_used) {
   PERF_TIMER_GUARD(write_pre_and_post_process_time);
-  StopWatch write_sw(immutable_db_options_.clock, immutable_db_options_.stats,
-                     DB_WRITE);
+  StopWatch write_sw(immutable_db_options_.clock, stats_, DB_WRITE);
 
   WriteContext write_context;
 
@@ -629,8 +627,7 @@ Status DBImpl::UnorderedWriteMemtable(const WriteOptions& write_options,
                                       SequenceNumber seq,
                                       const size_t sub_batch_cnt) {
   PERF_TIMER_GUARD(write_pre_and_post_process_time);
-  StopWatch write_sw(immutable_db_options_.clock, immutable_db_options_.stats,
-                     DB_WRITE);
+  StopWatch write_sw(immutable_db_options_.clock, stats_, DB_WRITE);
 
   WriteThread::Writer w(write_options, my_batch, callback, log_ref,
                         false /*disable_memtable*/);
@@ -685,8 +682,7 @@ Status DBImpl::WriteImplWALOnly(
   WriteThread::Writer w(write_options, my_batch, callback, log_ref,
                         disable_memtable, sub_batch_cnt, pre_release_callback);
   RecordTick(stats_, WRITE_WITH_WAL);
-  StopWatch write_sw(immutable_db_options_.clock, immutable_db_options_.stats,
-                     DB_WRITE);
+  StopWatch write_sw(immutable_db_options_.clock, stats_, DB_WRITE);
 
   write_thread->JoinBatchGroup(&w);
   assert(w.state != WriteThread::STATE_PARALLEL_MEMTABLE_WRITER);