log compaction output file's level along with number

Author: ideawu

db/db_impl.cc

@@ -821,8 +821,9 @@ Status DBImpl::FinishCompactionOutputFile(CompactionState* compact,
     delete iter;
     if (s.ok()) {
       Log(options_.info_log,
-          "Generated table #%llu: %lld keys, %lld bytes",
+          "Generated table #%llu@%d: %lld keys, %lld bytes",
           (unsigned long long) output_number,
+		  compact->compaction->level(),
           (unsigned long long) current_entries,
           (unsigned long long) current_bytes);
     }