fix_sst_dump_for_old_sst_format

Summary:
1. fix segment error when dumping old sst format (no properties nor stats)
2. Enable dumpping old sst format

Test Plan:
Generate block based sst file with "properties", and one with "stats" and one without neither.
Read it using sst_dump

Reviewers: ljin, igor, yhchiang, dhruba, sdong

Reviewed By: sdong

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D21837

tools/sst_dump.cc

@@ -54,6 +54,7 @@ class SstFileReader {
   Status ReadTableProperties(uint64_t table_magic_number,
                              RandomAccessFile* file, uint64_t file_size);
   Status SetTableOptionsByMagicNumber(uint64_t table_magic_number);
+  Status SetOldTableOptions();
 
   std::string file_name_;
   uint64_t read_num_;
@@ -112,9 +113,11 @@ Status SstFileReader::NewTableReader(const std::string& file_path) {
       options_.env->NewRandomAccessFile(file_path, &file_, soptions_);
     }
     options_.comparator = &internal_comparator_;
-    s = ReadTableProperties(magic_number, file_.get(), file_size);
-    if (s.ok()) {
-      s = SetTableOptionsByMagicNumber(magic_number);
+    // For old sst format, ReadTableProperties might fail but file can be read
+    if (ReadTableProperties(magic_number, file_.get(), file_size).ok()) {
+      SetTableOptionsByMagicNumber(magic_number);
+    } else {
+      SetOldTableOptions();
     }
   }
 
@@ -129,11 +132,15 @@ Status SstFileReader::NewTableReader(const std::string& file_path) {
 Status SstFileReader::ReadTableProperties(uint64_t table_magic_number,
                                           RandomAccessFile* file,
                                           uint64_t file_size) {
-  TableProperties* table_properties;
+  TableProperties* table_properties = nullptr;
   Status s = rocksdb::ReadTableProperties(file, file_size, table_magic_number,
                                           options_.env, options_.info_log.get(),
                                           &table_properties);
+  if (s.ok()) {
     table_properties_.reset(table_properties);
+  } else {
+    fprintf(stdout, "Not able to read table properties\n");
+  }
   return s;
 }
 
@@ -180,6 +187,14 @@ Status SstFileReader::SetTableOptionsByMagicNumber(
   return Status::OK();
 }
 
+Status SstFileReader::SetOldTableOptions() {
+  assert(table_properties_ == nullptr);
+  options_.table_factory = std::make_shared<BlockBasedTableFactory>();
+  fprintf(stdout, "Sst file format: block-based(old version)\n");
+
+  return Status::OK();
+}
+
 Status SstFileReader::ReadSequential(bool print_kv,
                                      uint64_t read_num,
                                      bool has_from,