Fix memory leak

Summary: There is a memory leak because TransformRepFactory does not delete its SliceTransform pointer. This patch adds a delete to the destructor.

Test Plan:
make check
make valgrind_check

Reviewers: dhruba, emayanke, haobo

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12513

include/rocksdb/memtablerep.h

@@ -180,7 +180,8 @@ public:
 // over the entire collection is rare.
 //
 // Parameters:
-//   transform: The SliceTransform to bucket user keys on.
+//   transform: The SliceTransform to bucket user keys on. TransformRepFactory
+//     assumes it does not own the pointer.
 //   bucket_count: Passed to the constructor of the underlying
 //     std::unordered_map of each TransformRep. On initialization, the
 //     underlying array will be at least bucket_count size.
@@ -206,9 +207,13 @@ public:
 //
 // Parameters: See TransformRepFactory.
 class UnsortedRepFactory : public TransformRepFactory {
+  const SliceTransform* transform_;
 public:
   explicit UnsortedRepFactory(size_t bucket_count = 0, size_t num_locks = 1000)
-    : TransformRepFactory(NewNoopTransform(), bucket_count, num_locks) { }
+    : TransformRepFactory(transform_ = NewNoopTransform(),
+                          bucket_count,
+                          num_locks) { }
+  virtual ~UnsortedRepFactory() { delete transform_; }
 };
 
 // PrefixHashReps bin user keys based on a fixed-size prefix. This optimizes for

util/transformrep.cc

@@ -149,7 +149,8 @@ class PrefixHashRep : public TransformRep {
  public:
   PrefixHashRep(const KeyComparator& compare, Arena* arena,
     const SliceTransform* transform, size_t bucket_size,
-    size_t num_locks) : TransformRep(compare, arena, transform,
+    size_t num_locks)
+  : TransformRep(compare, arena, transform,
     bucket_size, num_locks) { }
 
   virtual std::shared_ptr<MemTableRep::Iterator> GetPrefixIterator(