NDB 按 StructuredProperty 的属性排序 [英] NDB ordering by property of StructuredProperty

问题描述

假设我有一个 ndb.Model 类，我想将它用作另一个模型类上的 StructuredProperty:

class CommonExtraData(ndb.Model):计数 = ndb.IntegerProperty(required=True)类 MyObject(ndb.Model):名称 = ndb.StringProperty(required=True)额外 = ndb.StructuredProperty(CommonExtraData, required=True)

然后我可以做这样的查询吗:

MyObject.query().order(-MyObject.extra.count)

我在文档中找不到示例，并且由于我努力从旧 API 重构为 NDB，我的开发环境目前无法正常工作.

解决方案

刚刚做了一些实验，它似乎奏效了.你应该能够完全按照你写的去做.

在试验中，我发现了一个应该注意的怪癖 - 如果您使用重复属性，它似乎只对重复属性的第一个实例进行排序.例如，如果您的重复属性有 [CommonExtraData(count=5), CommonExtraData(count=1)] 和另一个有 [CommonExtraData(count=7), CommonExtraData(count=2)]，它会这样排序:

[CommonExtraData(count=7), CommonExtraData(count=2)][CommonExtraData(count=5), CommonExtraData(count=1)]

Say I have an ndb.Model class that I want to use as a StructuredProperty on another model class:

class CommonExtraData(ndb.Model):
    count = ndb.IntegerProperty(required=True)

class MyObject(ndb.Model):
    name = ndb.StringProperty(required=True)
    extra = ndb.StructuredProperty(CommonExtraData, required=True)

Could I then do a query like this:

MyObject.query().order(-MyObject.extra.count)

I can't find an example in the docs, and my dev environment is not currently working due to my endeavors of refactoring from the old API to NDB.

解决方案

Just did a bit of experimentation and it appears to be working. You should be able to do it exact as you wrote out.

In experimenting, I found one quirk that should be noted - if you use repeated property, it appears to sort on the first instance of the repeated property only. For example, if your repeated property had [CommonExtraData(count=5), CommonExtraData(count=1)] and another had [CommonExtraData(count=7), CommonExtraData(count=2)], it would sort like this:

[CommonExtraData(count=7), CommonExtraData(count=2)] [CommonExtraData(count=5), CommonExtraData(count=1)]

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