components/sync/protocol/entity_metadata.proto

// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// If you change or add any fields in this file, update proto_visitors.h and
// potentially proto_enum_conversions.{h, cc}.

syntax = "proto2";

option optimize_for = LITE_RUNTIME;

package sync_pb;

import "unique_position.proto";

// Sync proto to store entity metadata in model type storage.
message EntityMetadata {
  // A hash based on the client tag and model type.
  // Used for various map lookups. Should always be available.
  // Sent to the server as SyncEntity::client_defined_unique_tag.
  optional string client_tag_hash = 1;

  // The entity's server-assigned ID.
  //
  // Prior to the item's first commit, we leave this value as an empty string.
  // The initial ID for a newly created item has to meet certain uniqueness
  // requirements, and we handle those on the sync thread.
  optional string server_id = 2;

  // Whether or not the entity is deleted.
  optional bool is_deleted = 3;

  // A version number used to track in-progress commits. Each local change
  // increments this number.
  optional int64 sequence_number = 4;

  // The sequence number of the last item known to be successfully committed.
  optional int64 acked_sequence_number = 5;

  // The server version on which this item is based.
  //
  // If there are no local changes, this is the version of the entity as we see
  // it here.
  //
  // If there are local changes, this is the version of the entity on which
  // those changes are based.
  optional int64 server_version = 6 [default = -1];

  // Entity creation and modification timestamps. Assigned by the client and
  // synced by the server, though the server usually doesn't bother to inspect
  // their values. They are encoded as milliseconds since the Unix epoch.
  optional int64 creation_time = 7;
  optional int64 modification_time = 8;

  // A hash of the current entity specifics value. Used to detect whether
  // entity's specifics value has changed without having to keep specifics in
  // memory.
  optional string specifics_hash = 9;

  // A hash of the last specifics known by both the client and server. Used to
  // detect when local commits and remote updates are just for encryption. This
  // value will be the empty string only in the following cases: the entity is
  // in sync with the server, has never been synced, or is deleted.
  optional string base_specifics_hash = 10;

  // Used for positioning entities among their siblings. Relevant only for data
  // types that support positions (e.g bookmarks). Refer to its definition in
  // unique_position.proto for more information about its internal
  // representation.
  optional UniquePosition unique_position = 11;
}