Simplified level_ptrs by using a std:vector

Summary: Simplified level_ptrs by using a std:vector

Test Plan: make check

Reviewers: sheki, emayanke

Reviewed By: emayanke

CC: leveldb

Differential Revision: https://reviews.facebook.net/D10245

db/version_set.cc

@@ -2169,16 +2169,15 @@ Compaction::Compaction(int level, uint64_t target_file_size,
       overlapped_bytes_(0),
       base_index_(-1),
       parent_index_(-1),
-      score_(0) {
+      score_(0),
+      level_ptrs_(std::vector<size_t>(number_levels)) {
   edit_ = new VersionEdit(number_levels_);
-  level_ptrs_ = new size_t[number_levels_];
   for (int i = 0; i < number_levels_; i++) {
     level_ptrs_[i] = 0;
   }
 }
 
 Compaction::~Compaction() {
-  delete[] level_ptrs_;
   delete edit_;
   if (input_version_ != nullptr) {
     input_version_->Unref();

db/version_set.h

@@ -567,7 +567,7 @@ class Compaction {
   // is that we are positioned at one of the file ranges for each
   // higher level than the ones involved in this compaction (i.e. for
   // all L >= level_ + 2).
-  size_t* level_ptrs_;
+  std::vector<size_t> level_ptrs_;
 
   // mark (or clear) all files that are being compacted
   void MarkFilesBeingCompacted(bool);