问题描述
我正在开发一个PHP应用程序，我们需要在某个边界内检索结果，但是按结果的创建日期排序，而不是距离。我认为MongoDB的geoNear命令对此很有用，因为它负责计算每个结果的距离。但是，我想知道是否有一种方法可以通过create_date属性指定排序，而不是距离。理想情况下，我会创建坐标的复合键索引并创建日期，然后快速检索按创建日期排序的特定区域中的所有结果。
I'm developing a PHP application in which we need to retrieve results within a certain boundary, but ordered by the create date of the results, not the distance. I figured MongoDB's geoNear command would be great for this, since it takes care of calculating the distance for each result. However, I was wondering if there was a way to specify sorting by the create_date attribute, rather than distance. Ideally I would create a compound key index of coordinates and create date, and then quickly retrieve all results in a specific area ordered by create date.
这是可能的，还是必须的我的排序后查询？
Is this possible, or must I do my sorting post-query?
推荐答案
如果您使用 $在命令附近，你必须先按距离排序，否则近的概念实际上没有任何意义。在地球上，一切都可以接近给定点，这只是一个多近的问题。
If you're using the $near command then you have to first sort by distance or the concept of "near" doesn't really make any sense. On a globe everything can be "near" to a given point, it's just an issue of "how near".
这里有两个选择：
- 限制
$附近的结果 - 使用
$命令
- limit the results of
$near - use the
$withincommand
我认为你要找的是 $ 命令
center = [50, 50]
radius = 10
db.places.find({"loc" : {"$within" : {"$center" : [center, radius]}}})
然后你可以用其他键来对它们进行排序：
You can then sort these by some other key:
db.places.find(...).sort({created:1})
但是，within命令可能提供太多结果，所以你可能想要一些逻辑来限制 $在中返回的项目数。
However, the within command may provide too many results, so you probably want to put some logic to limit the number of items returned by $within.
db.places.find(...).limit(50).sort({created:1})
如果达到特定限制，真相就是 $ 命令通常会开始下降。您的客户端代码可能想要检查您是否达到最大结果。
Truth is, if you hit a specific limit, the value of your $within command generally begins to drop. Your client code may want to check if you're hitting the max results.
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