在应用引擎数据存储中查询缺少属性的实体? [英] Querying for entities with missing properties in app engine Datastore?
问题描述
class示例(db.Model):
row_num = db.InteProProperty(required = True)
updated = db.IntegerProperty()
...
...
现在,当我存储值时,我可能无法每次填充更新属性的值,这意味着在某些实体中它可能不存在。
我想构建一个数据存储查询,以便我可以获取没有属性更新集的所有类实例。
我该怎么做?
p.s。我知道我可以设置一个默认值,然后查询它。但问题是我有超过300万个实体,并且更新将仅标记为1%,因此我不想通过将其余的设置为0来浪费太多的数据存储空间。
<在GQL中,没有属性值的对象不能通过该属性的查询返回,所以如果没有默认值,你所要求的是不可能的 b
参考资料:此页面。
I have a model which looks like this:
class Example (db.Model) :
row_num = db.IntegerProperty(required=True)
updated = db.IntegerProperty()
...
...
Now when i store values, I may not fill the value for the updated property every time, which implies that in some entities it may not exist.
I want to construct a datastore query so that i can get all entities of kind Example which do not have the property updated set.
How do i do this?
p.s. i know i can set a default value and then query on it. But the issue is i have over 3 million entities and updated will be marked only for 1% of them, so i do not want to waste so much of datastore space by setting the rest to 0.
In GQL, objects which do not have a value for a property cannot be returned by queries on that property, so what you're asking for is impossible without a default value.
Reference: section headed "Entities Without a Filtered Property Are Never Returned by a Query" on this page.
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