查询相同类型的根实体和子实体时，数据存储区是否需要指定祖先？

Question

For example, take the following snippet from the provided appengine-angular-gotodos :

func getAllTodos(c appengine.Context) ([]Todo, error) {
    todos := []Todo{}
    ks, err := datastore.NewQuery("Todo").Ancestor(defaultTodoList(c)).Order("Created").GetAll(c, &todos)
    if err != nil {
        return nil, err
    }
    for i := 0; i < len(todos); i++ {
        todos[i].Id = ks[i].IntID()
    }
    return todos, nil
}

If you change the query to not include .Ancestor(defaultTodoList(c)). the function fails to return any todo results.

• If an entity is saved with an ancestry, must you query it by that ancestor?
• How do you query for Entities regardless of whether they are children, or root entities?
• What are the performance and architecture considerations I should make when modeling my app given the need to do ancestor-less queries?

Answer 1

defaultTodoList(c) might not contain the parent Entity that the code expects it to contain. Try to verify its value somehow before using it, for example by storing it in a variable and then logging data out of it.