update DB::AddFile to ingest list of sst files

Summary:
DB::AddFile(std::string file_path) API that allow them to ingest an SST file created using SstFileWriter
We want to update this interface to be able to accept a list of files that will be ingested, DB::AddFile(std::vector<std::string> file_path_list).

Test Plan:
Add test case `AddExternalSstFileList` in `DBSSTTest`. To make sure:
1. files key ranges are not overlapping with each other
2. each file key range dont overlap with the DB key range
3. make sure no snapshots are held

Reviewers: andrewkr, sdong, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D58587

db/db_impl.cc

@@ -6,7 +6,6 @@
 // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file. See the AUTHORS file for names of contributors.
-
 #include "db/db_impl.h"
 
 #ifndef __STDC_FORMAT_MACROS

db/db_impl.h

@@ -258,10 +258,11 @@ class DBImpl : public DB {
 
   using DB::AddFile;
   virtual Status AddFile(ColumnFamilyHandle* column_family,
-                         const ExternalSstFileInfo* file_info,
+                         const std::vector<ExternalSstFileInfo>& file_info_list,
                          bool move_file) override;
   virtual Status AddFile(ColumnFamilyHandle* column_family,
-                         const std::string& file_path, bool move_file) override;
+                         const std::vector<std::string>& file_path_list,
+                         bool move_file) override;
 
 #endif  // ROCKSDB_LITE
 
@@ -637,13 +638,17 @@ class DBImpl : public DB {
   // Finds the lowest level in the DB that the ingested file can be added to
   // REQUIRES: mutex_ held
   int PickLevelForIngestedFile(ColumnFamilyData* cfd,
-                               const ExternalSstFileInfo* file_info);
+                               const ExternalSstFileInfo& file_info);
 
   Status CompactFilesImpl(
       const CompactionOptions& compact_options, ColumnFamilyData* cfd,
       Version* version, const std::vector<std::string>& input_file_names,
       const int output_level, int output_path_id, JobContext* job_context,
       LogBuffer* log_buffer);
+  Status ReadExternalSstFileInfo(ColumnFamilyHandle* column_family,
+                                 const std::string& file_path,
+                                 ExternalSstFileInfo* file_info);
+
 #endif  // ROCKSDB_LITE
 
   ColumnFamilyData* GetColumnFamilyDataByName(const std::string& cf_name);