javascript - 是否可以中止 IndexedDB 升级事件？

Question

我正在尝试实现一个 IndexedDB 接口(interface)，该接口(interface)允许用户从以前的数据库 (DB) 版本(在 onupgradeneeded 处理程序中检测到 oldVersion，event.target.oldVersion) 到最新版本(currentVersion 即将开放)，这意味着我需要:

1. 取消或中止currentVersion开启操作
2. 打开以前的数据库(在onupgradeneeded 中检测到oldVersion)
3. 读取它的数据
4. 关闭数据库
5. (继续打开 currentVersion 数据库的正常过程)

我在打开 oldVersion 时遇到问题，因为我无法中止(异常 11)currentVersion 升级事件(它也是 not cancelable )。

Exception 11: An operation was called on an object on which it is not allowed or at a time when it is not allowed.

是否有可能以某种方式取消或中止 currentVersion 的升级事件，以便我打开 oldVersion...？

注意:...如果没有，是否有任何其他方法可以从我缺少的旧版本数据库中迁移数据？

Answer 1

Is it possible to somehow cancel or abort the upgrade event for currentVersion, in order for me to open the oldVersion...?

var rq = indexedDB.open(name, ver);
rq.onupgradeneeded = function(e) {
  rq.transaction.abort();
};
rq.onsuccess = function(e) { console.log('THIS SHOULD NOT RUN'); };
rq.onerror = function(e) { console.log('This should run'); };

is there anyother way to migrate data from older versions of a DB that I'm missing?

通常这就是 upgradeneeded 的全部目的 - 在提供给您的 verionchange 事务期间，您从旧版本迁移数据和模式。

var rq = indexedDB.open(name, 2);
rq.onupgradeneeded = function(e) {
  var db = rq.result;
  if (e.oldVersion < 1) {
    // database didn't exist at all, create new schema
    db.createObjectStore('store2');
  } else if (e.oldVersion < 2) {
    // do the migration - assumes v1 had 'store1'
    var store1 = rq.transaction.objectStore('store1');
    var store2 = db.createObjectStore('store2');
    var r = store1.openCursor();
    r.onsuccess = function() {
      var cursor = r.result;
      if (cursor) {
        store2.put(cursor.value, cursor.key);
        cursor.continue();
      } else {
        // migration done, delete old store
        db.deleteObjectStore('store1');
      }
    };
  }
};