[英]How to use $geoNear with aggregate in PyMongo
假设您有一个具有以下结构的集合:
{
"_id": ObjectId("543f1ec50204444c53ba39a0"),
"request_ip": "61.111.36.11",
"owner": ObjectId("543f227c0204444c53ba4b28"),
"loc": [-116.199, 43.6186]
}
其中loc
包含一个地理点的位置,分别由其纬度和经度定义。
好吧,您需要的是根据位置与另一个给定点之间的距离计算出集合中的文档。
在这种情况下,将使用aggregate ()
函数:
cercanos = collection.aggregate(
[{
"$geoNear": {
"near": [ 52.15077 , 9.95112 ],
"distanceField": "dist",
"spherical": True,
"limit":2
}
}])
当您遵循MongoDB文档( https://docs.mongodb.com/manual/reference/operator/aggregation/geoNear )时,一切似乎都井然有序,但是,当您运行时会出现一些错误:
Traceback (most recent call last):
File "E:\Documents\EclipseProjects\Bonus8\src\pru.py", line 154, in <module>
"spherical": True,
File "D:\Python\lib\site-packages\pymongo\collection.py", line 1870, in aggregate
collation=collation)
File "D:\Python\lib\site-packages\pymongo\collection.py", line 232, in _command
collation=collation)
File "D:\Python\lib\site-packages\pymongo\pool.py", line 419, in command
collation=collation)
File "D:\Python\lib\site-packages\pymongo\network.py", line 116, in command
parse_write_concern_error=parse_write_concern_error)
File "D:\Python\lib\site-packages\pymongo\helpers.py", line 210, in _check_command_response
raise OperationFailure(msg % errmsg, code, response)
pymongo.errors.OperationFailure: geoNear command failed: { ok: 0.0, errmsg: "no geo indices for geoNear" }
发生什么事:
问题在于,MongoDB参考手册提供的用法示例特定于控制台内的独占执行( mongo shell
)。 这会导致在PyMongo环境中进行重大更改,例如必须引用变量。
可能的解决方案:
创建地理空间索引:
from pymongo import GEO2D
collection.create_index([("loc", GEO2D)])
这指定了二维地理空间索引并解决了先前发生的错误。
输出:
{
"_id": ObjectId("543f1ec50204444c53ba39a0"),
"request_ip": "61.111.36.11",
"owner": ObjectId("543f227c0204444c53ba4b28"),
"loc": [-116.199, 43.6186]
"dist": 2.18848713
}
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