1 files changed, 71 insertions, 0 deletions
diff --git a/src/rocksdb/db/version_util.h b/src/rocksdb/db/version_util.h
new file mode 100644
index 000000000..5ec6fda11
--- /dev/null
+++ b/src/rocksdb/db/version_util.h
@@ -0,0 +1,71 @@
+//  Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+
+#pragma once
+
+#include "db/version_set.h"
+
+namespace ROCKSDB_NAMESPACE {
+
+// Instead of opening a `DB` to perform certain manifest updates, this
+// uses the underlying `VersionSet` API to read and modify the MANIFEST. This
+// allows us to use the user's real options, while not having to worry about
+// the DB persisting new SST files via flush/compaction or attempting to read/
+// compact files which may fail, particularly for the file we intend to remove
+// (the user may want to remove an already deleted file from MANIFEST).
+class OfflineManifestWriter {
+ public:
+  OfflineManifestWriter(const DBOptions& options, const std::string& db_path)
+      : wc_(options.delayed_write_rate),
+        wb_(options.db_write_buffer_size),
+        immutable_db_options_(WithDbPath(options, db_path)),
+        tc_(NewLRUCache(1 << 20 /* capacity */,
+                        options.table_cache_numshardbits)),
+        versions_(db_path, &immutable_db_options_, sopt_, tc_.get(), &wb_, &wc_,
+                  /*block_cache_tracer=*/nullptr, /*io_tracer=*/nullptr,
+                  /*db_id*/ "", /*db_session_id*/ "") {}
+
+  Status Recover(const std::vector<ColumnFamilyDescriptor>& column_families) {
+    return versions_.Recover(column_families, /*read_only*/ false,
+                             /*db_id*/ nullptr,
+                             /*no_error_if_files_missing*/ true);
+  }
+
+  Status LogAndApply(ColumnFamilyData* cfd, VersionEdit* edit,
+                     FSDirectory* dir_contains_current_file) {
+    // Use `mutex` to imitate a locked DB mutex when calling `LogAndApply()`.
+    InstrumentedMutex mutex;
+    mutex.Lock();
+    Status s = versions_.LogAndApply(cfd, *cfd->GetLatestMutableCFOptions(),
+                                     edit, &mutex, dir_contains_current_file,
+                                     false /* new_descriptor_log */);
+    mutex.Unlock();
+    return s;
+  }
+
+  VersionSet& Versions() { return versions_; }
+  const ImmutableDBOptions& IOptions() { return immutable_db_options_; }
+
+ private:
+  WriteController wc_;
+  WriteBufferManager wb_;
+  ImmutableDBOptions immutable_db_options_;
+  std::shared_ptr<Cache> tc_;
+  EnvOptions sopt_;
+  VersionSet versions_;
+
+  static ImmutableDBOptions WithDbPath(const DBOptions& options,
+                                       const std::string& db_path) {
+    ImmutableDBOptions rv(options);
+    if (rv.db_paths.empty()) {
+      // `VersionSet` expects options that have been through
+      // `SanitizeOptions()`, which would sanitize an empty `db_paths`.
+      rv.db_paths.emplace_back(db_path, 0 /* target_size */);
+    }
+    return rv;
+  }
+};
+
+}  // namespace ROCKSDB_NAMESPACE