ColumnFamilyOptions SanitizeOptions is buggy on 32-bit platforms.

Summary:
The pre-existing code is trying to clamp between 65,536 and 0,
resulting in clamping to 65,536, resulting in very small buffers,
resulting in ShouldFlushNow() being true quite easily,
resulting in assertion failing and database performance
being "not what it should be".

https://github.com/facebook/rocksdb/issues/1018

Test Plan: make check

Reviewers: sdong, andrewkr, IslamAbdelRahman, yhchiang, igor

Reviewed By: igor

Subscribers: leveldb, andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D55455

db/column_family.cc

@@ -147,13 +147,10 @@ ColumnFamilyOptions SanitizeOptions(const DBOptions& db_options,
                                     const ColumnFamilyOptions& src) {
   ColumnFamilyOptions result = src;
   result.comparator = icmp;
-#ifdef OS_MACOSX
-  // TODO(icanadi) make write_buffer_size uint64_t instead of size_t
-  ClipToRange(&result.write_buffer_size, ((size_t)64) << 10, ((size_t)1) << 30);
-#else
-  ClipToRange(&result.write_buffer_size,
-              ((size_t)64) << 10, ((size_t)64) << 30);
-#endif
+  size_t clamp_max = std::conditional<
+      sizeof(size_t) == 4, std::integral_constant<size_t, 0xffffffff>,
+      std::integral_constant<size_t, 64ull << 30>>::type::value;
+  ClipToRange(&result.write_buffer_size, ((size_t)64) << 10, clamp_max);
   // if user sets arena_block_size, we trust user to use this value. Otherwise,
   // calculate a proper value from writer_buffer_size;
   if (result.arena_block_size <= 0) {