Firestore 查询 orderBy 不起作用? [英] Firestore query orderBy not working?

问题描述

FutureBuilder 在类型时间戳字段上执行 Firestore 查询返回快照中没有数据.但是，没有 orderBy 的相同查询也可以正常工作.
我错过了什么?感谢您的帮助.

FutureBuilder with a Firestore query on a field of Type timestamp comes back with no data in snapshot. However, the same query without the orderBy works just fine.
What am I missing ? Thanks for the help.

// Working code
future: Firestore.instance.collection('messages').where('toid',isEqualTo: _emailID).getDocuments(),
builder: (context, snapshot) ...

// Not Working - returns to if(!snapshot.hasData)
future: Firestore.instance.collection('messages').where('toid',isEqualTo: _emailID).orderBy('_timeStampUTC', descending: true).getDocuments(),
builder: (context, snapshot) ...

推荐答案

我认为你在这里缺少一个 ' '_timeStampUTC，所以它应该是:

I think you are missing a ' here '_timeStampUTC, so it should be:

 orderBy('_timeStampUTC', descending: true)

此外，您需要确保为 toid 和其他_timeStampUTC 创建索引，当您尝试按不在您是查询的位置.

Also, you need to be sure to create an index for toid and other for _timeStampUTC, this is done when you try to order by a property that is not in you the where of the query.

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