Remove unused classes

Summary: This is a followup diff for https://reviews.facebook.net/D15447, which picks the most simple task: delete some unused memtable reps.

Test Plan: make

Reviewers: haobo, dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D15585

include/rocksdb/memtablerep.h

@@ -180,86 +180,7 @@ public:
   }
 };
 
-// HashSkipListRep is backed by hash map of buckets. Each bucket is a skip
+// This class contains a fixed array of buckets, each
-// list. All the keys with the same prefix will be in the same bucket.
-// The prefix is determined using user supplied SliceTransform. It has
-// to match prefix_extractor in options.prefix_extractor.
-//
-// Iteration over the entire collection is implemented by dumping all the keys
-// into a separate skip list. Thus, these data structures are best used when
-// iteration over the entire collection is rare.
-//
-// Parameters:
-//   transform: The SliceTransform to bucket user keys on. TransformRepFactory
-//     owns 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.
-//   num_locks: Number of read-write locks to have for the rep. Each bucket is
-//     hashed onto a read-write lock which controls access to that lock. More
-//     locks means finer-grained concurrency but more memory overhead.
-class TransformRepFactory : public MemTableRepFactory {
- public:
-  explicit TransformRepFactory(const SliceTransform* transform,
-    size_t bucket_count, size_t num_locks = 1000)
-    : transform_(transform),
-      bucket_count_(bucket_count),
-      num_locks_(num_locks) { }
-
-  virtual ~TransformRepFactory() { delete transform_; }
-
-  virtual MemTableRep* CreateMemTableRep(MemTableRep::KeyComparator&,
-                                         Arena*) override;
-
-  virtual const char* Name() const override {
-    return "TransformRepFactory";
-  }
-
-  const SliceTransform* GetTransform() { return transform_; }
-
- protected:
-  const SliceTransform* transform_;
-  const size_t bucket_count_;
-  const size_t num_locks_;
-};
-
-// UnsortedReps bin user keys based on an identity function transform -- that
-// is, transform(key) = key. This optimizes for point look-ups.
-//
-// Parameters: See TransformRepFactory.
-class UnsortedRepFactory : public TransformRepFactory {
-public:
-  explicit UnsortedRepFactory(size_t bucket_count = 0, size_t num_locks = 1000)
-    : TransformRepFactory(NewNoopTransform(),
-                          bucket_count,
-                          num_locks) { }
-  virtual const char* Name() const override {
-    return "UnsortedRepFactory";
-  }
-};
-
-// PrefixHashReps bin user keys based on a fixed-size prefix. This optimizes for
-// short ranged scans over a given prefix.
-//
-// Parameters: See TransformRepFactory.
-class PrefixHashRepFactory : public TransformRepFactory {
-public:
-  explicit PrefixHashRepFactory(const SliceTransform* prefix_extractor,
-    size_t bucket_count = 0, size_t num_locks = 1000)
-    : TransformRepFactory(prefix_extractor, bucket_count, num_locks)
-    { }
-
-  virtual MemTableRep* CreateMemTableRep(MemTableRep::KeyComparator&,
-                                         Arena*) override;
-
-  virtual const char* Name() const override {
-    return "PrefixHashRepFactory";
-  }
-};
-
-// The same as TransformRepFactory except it doesn't use locks.
-// Experimental, will replace TransformRepFactory once we are sure
-// it performs better. It contains a fixed array of buckets, each
 // pointing to a skiplist (null if the bucket is empty).
 // bucket_count: number of fixed array buckets
 // skiplist_height: the max height of the skiplist