Question

我正在尝试检查字段的第一个字符是不是a-z

db.zips.aggregate( 
 [
{ $group : { city: { $regex: '^[a-z]', $options: 'i' }, n : {$sum:1} } }
 ]
)

这是一个预期会找到的示例文档，但查询错误与未知运算符'$ regex'有关。已安装MongoDB v2.4.5：

{"city": "25536", "loc": [-82.076761, 38.087553], "pop": 61, "state": "WV", "_id":   "25536"}

错误：

Error: Printing Stack Trace
at printStackTrace (src/mongo/shell/utils.js:37:15)
at DBCollection.aggregate (src/mongo/shell/collection.js:897:9)
at (shell):1:9
Wed Jul 31 12:14:14.737 JavaScript execution failed: aggregate failed: {
    "errmsg" : "exception: unknown group operator '$regex'",
    "code" : 15952,
    "ok" : 0
} at src/mongo/shell/collection.js:L898

谢谢！

P.S。我也尝试了这个：

db.zips.aggregate( 
[
{ $project : { city: /^[a-z]/i }}
,{ $group : { city : "$city", n : {$sum:1} } }
]
)

Error: Printing Stack Trace
at printStackTrace (src/mongo/shell/utils.js:37:15)
at DBCollection.aggregate (src/mongo/shell/collection.js:897:9)
at (shell):1:9
Wed Jul 31 12:26:21.531 JavaScript execution failed: aggregate failed: {
    "errmsg" : "exception: disallowed field type RegEx in object expression
(at 'city')",
    "code" : 15992,
    "ok" : 0
} at src/mongo/shell/collection.js:L898

看来，我尝试使用正则表达式的方法不正确或者位置/操作不正确。

Answer 1

$ regex不能在那里使用，你想看这样的JIRA：https://jira.mongodb.org/browse/SERVER-8892

但是，我认为您实际上希望通过正则表达式而不是组来$match。所以你想要符合你标准中的所有城市，然后你想把它们分组。

这里提到的是一个重复的问题，我刚刚通过谷歌搜索找到：using $regex in mongodb aggregation framework in $group

mongodb $ regex错误：未知运算符

1 个答案: