Add virtual func IsDeleteRangeSupported

Summary:
this modify allows third-party tables able to support delete range
Closes https://github.com/facebook/rocksdb/pull/2035

Differential Revision: D5407973

Pulled By: ajkr

fbshipit-source-id: 82e364b7dd5a198660788d59543f15b8f95cc418

db/column_family.cc

@@ -355,8 +355,8 @@ ColumnFamilyData::ColumnFamilyData(
       initial_cf_options_(SanitizeOptions(db_options, cf_options)),
       ioptions_(db_options, initial_cf_options_),
       mutable_cf_options_(initial_cf_options_),
-      is_delete_range_supported_(strcmp(cf_options.table_factory->Name(),
-                                        BlockBasedTableFactory().Name()) == 0),
+      is_delete_range_supported_(
+          cf_options.table_factory->IsDeleteRangeSupported()),
       write_buffer_manager_(write_buffer_manager),
       mem_(nullptr),
       imm_(ioptions_.min_write_buffer_number_to_merge,

include/rocksdb/table.h

@@ -482,6 +482,9 @@ class TableFactory {
   // Developers should use DB::SetOption() instead to dynamically change
   // options while the DB is open.
   virtual void* GetOptions() { return nullptr; }
+
+  // Return is delete range supported
+  virtual bool IsDeleteRangeSupported() const { return false; }
 };
 
 #ifndef ROCKSDB_LITE

table/block_based_table_factory.h

@@ -55,6 +55,8 @@ class BlockBasedTableFactory : public TableFactory {
 
   void* GetOptions() override { return &table_options_; }
 
+  bool IsDeleteRangeSupported() const override { return true; }
+
  private:
   BlockBasedTableOptions table_options_;
 };