Eliminate compiler complaining, which the return type of the function… (#8498)

Summary:
… should be uint64_t.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8498

Reviewed By: jay-zhuang

Differential Revision: D29605064

Pulled By: ajkr

fbshipit-source-id: e431448ac9d8a37ae83679c4cc5732e29fe49de4

db/db_impl/db_impl.h

@@ -965,7 +965,7 @@ class DBImpl : public DB {
 
   // Return the maximum overlapping data (in bytes) at next level for any
   // file at a level >= 1.
-  int64_t TEST_MaxNextLevelOverlappingBytes(
+  uint64_t TEST_MaxNextLevelOverlappingBytes(
       ColumnFamilyHandle* column_family = nullptr);
 
   // Return the current manifest file no.

db/db_impl/db_impl_debug.cc

@@ -43,7 +43,7 @@ bool DBImpl::TEST_WALBufferIsEmpty(bool lock) {
   return res;
 }
 
-int64_t DBImpl::TEST_MaxNextLevelOverlappingBytes(
+uint64_t DBImpl::TEST_MaxNextLevelOverlappingBytes(
     ColumnFamilyHandle* column_family) {
   ColumnFamilyData* cfd;
   if (column_family == nullptr) {

db/version_set.cc

@@ -3390,7 +3390,7 @@ const char* VersionStorageInfo::LevelFileSummary(FileSummaryStorage* scratch,
   return scratch->buffer;
 }
 
-int64_t VersionStorageInfo::MaxNextLevelOverlappingBytes() {
+uint64_t VersionStorageInfo::MaxNextLevelOverlappingBytes() {
   uint64_t result = 0;
   std::vector<FileMetaData*> overlaps;
   for (int level = 1; level < num_levels() - 1; level++) {

db/version_set.h

@@ -447,7 +447,7 @@ class VersionStorageInfo {
 
   // Return the maximum overlapping data (in bytes) at next level for any
   // file at a level >= 1.
-  int64_t MaxNextLevelOverlappingBytes();
+  uint64_t MaxNextLevelOverlappingBytes();
 
   // Return a human readable string that describes this version's contents.
   std::string DebugString(bool hex = false) const;