google-app-engine - 自动 ID 分配器会返回我在其他实体上任意设置的 ID 吗？

Question

如果我任意将新实体的 ID 设置为 1000，而不先使用 allocateIds，是否可以自动为后来的实体赋予 ID 1000 并覆盖我的原始实体？

在伪代码中，如果我有:

Entity e1;
e1.setId(1000);
datastore.put(e1);

...稍后...

Entity e2;
datastore.put(e2);

e2 是否有机会自动获得 ID 1000 并覆盖 e1？

Answer 1

如 Java API documentation 中所述

Creating an entity for the purpose of insertion (as opposed to update) with this constructor is discouraged unless the id was obtained from a key returned by a KeyRange obtained from AsyncDatastoreService.allocateIds(String, long) or DatastoreService.allocateIds(String, long) for the same kind.

另见 Python documentation :

Be aware, however, that the datastore is not guaranteed to avoid app-assigned IDs. It is possible, though unlikely, that the datastore will assign a numeric ID that will cause a conflict with an entity with an app-assigned ID. The only way to avoid this problem is to have your app use allocate_ids() to obtain a batch of IDs. The datastore's automatic ID generator will not use IDs that have been obtained using allocate_ids(), so your app can use these IDs without conflict.

您不应该使用数据存储尚未分配的 ID 创建实体，如果您想提供用户定义的标识符作为实体键的一部分，请改用 key_name。