Fix win build

Summary: Fixing error with win build where we compare int64_t with size_t.

Test Plan: make check

Reviewers: andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D57885

db/db_iterator_test.cc

@@ -1566,7 +1566,7 @@ TEST_F(DBIteratorTest, ReadAhead) {
   auto* iter = db_->NewIterator(read_options);
   iter->SeekToFirst();
   int64_t num_file_opens = TestGetTickerCount(options, NO_FILE_OPENS);
-  int64_t bytes_read = env_->random_read_bytes_counter_;
+  size_t bytes_read = env_->random_read_bytes_counter_;
   delete iter;
 
   env_->random_read_bytes_counter_ = 0;
@@ -1575,7 +1575,7 @@ TEST_F(DBIteratorTest, ReadAhead) {
   iter = db_->NewIterator(read_options);
   iter->SeekToFirst();
   int64_t num_file_opens_readahead = TestGetTickerCount(options, NO_FILE_OPENS);
-  int64_t bytes_read_readahead = env_->random_read_bytes_counter_;
+  size_t bytes_read_readahead = env_->random_read_bytes_counter_;
   delete iter;
   ASSERT_EQ(num_file_opens + 3, num_file_opens_readahead);
   ASSERT_GT(bytes_read_readahead, bytes_read);

db/db_test_util.h

@@ -359,7 +359,7 @@ class SpecialEnv : public EnvWrapper {
      public:
       CountingFile(unique_ptr<RandomAccessFile>&& target,
                    anon::AtomicCounter* counter,
-                   std::atomic<int64_t>* bytes_read)
+                   std::atomic<size_t>* bytes_read)
           : target_(std::move(target)),
             counter_(counter),
             bytes_read_(bytes_read) {}
@@ -374,7 +374,7 @@ class SpecialEnv : public EnvWrapper {
      private:
       unique_ptr<RandomAccessFile> target_;
       anon::AtomicCounter* counter_;
-      std::atomic<int64_t>* bytes_read_;
+      std::atomic<size_t>* bytes_read_;
     };
 
     Status s = target()->NewRandomAccessFile(f, r, soptions);
@@ -471,7 +471,7 @@ class SpecialEnv : public EnvWrapper {
 
   bool count_random_reads_;
   anon::AtomicCounter random_read_counter_;
-  std::atomic<int64_t> random_read_bytes_counter_;
+  std::atomic<size_t> random_read_bytes_counter_;
   std::atomic<int> random_file_open_counter_;
 
   bool count_sequential_reads_;