英文:
Mongodb aggregation in golang
问题
我有一个像这样的mongodb集合:
{
source: "...",
url: "...",
comments: [
.....
]
}
我想根据评论数量找到前5个文档。我可以使用以下命令提示符中的查询找到所需的结果:
db.gmsNews.aggregate([
{
$match:{source:"..."}
},
{
$unwind: "$comments"
},
{
$group: {
_id: "$url",
size: {
$sum: 1
},
}
},
{
$sort : { size : -1 }
},
{
$limit : 5
}
])
这给我以下输出:
{ "_id" : "...", "size" : 684 }
{ "_id" : "...", "size" : 150 }
现在我想使用mgo驱动程序将此查询转换为golang。我在以下方式中使用管道:
o1 := bson.M{
"$match" :bson.M {"source":"..."},
}
o2 := bson.M{
"$unwind": "$comments",
}
o3 := bson.M{
"$group": bson.M{
"_id": "$url",
"size": bson.M{
"$sum": 1,
},
},
}
o4 := bson.M{
"sort": bson.M{
"size": -1,
},
}
o5 := bson.M{
"$limit": 5,
}
operations := []bson.M{o1, o2, o3, o4, o5}
pipe := c.Pipe(operations)
// 运行查询并捕获结果
results := []bson.M{}
err1 := pipe.One(&results)
if err1 != nil {
fmt.Printf("ERROR : %s\n", err1.Error())
return
}
fmt.Printf("URL : %s, Size: %s\n", results[0]["_id"], results[0]["size"])
不幸的是,这不起作用,我得到以下输出:
ERROR : Unsupported document type for unmarshalling: []bson.M
想知道我做错了什么,如何解决。
非常感谢您的帮助。
提前致谢。
Ripul
英文:
I have a mongodb collection like this:
{
source: "...",
url: "...",
comments: [
.....
]
}
I would like to find the top 5 documents based on the number of comments. I can find the desired result using the following query in the command prompt:
db.gmsNews.aggregate([
{
$match:{source:"..."}
},
{
$unwind: "$comments"
},
{
$group: {
_id: "$url",
size: {
$sum: 1
},
}
},
{
$sort : { size : -1 }
},
{
$limit : 5
}
])
This gives me the following output:
{ "_id" : "...", "size" : 684 }
{ "_id" : "...", "size" : 150 }
Now I would like to translate this query into golang using the mgo driver. I am using the pipe for this in the following way:
o1 := bson.M{
"$match" :bson.M {"source":"..."},
}
o2 := bson.M{
"$unwind": "$comments",
}
o3 := bson.M{
"$group": bson.M{
"_id": "$url",
"size": bson.M{
"$sum": 1,
},
},
}
o4 := bson.M{
"sort": bson.M{
"size": -1,
},
}
o5 := bson.M{
"$limit": 5,
}
operations := []bson.M{o1, o2, o3, o4, o5}
pipe := c.Pipe(operations)
// Run the queries and capture the results
results := []bson.M{}
err1 := pipe.One(&results)
if err1 != nil {
fmt.Printf("ERROR : %s\n", err1.Error())
return
}
fmt.Printf("URL : %s, Size: %sn", results[0]["_id"], results[0]["size"])
Unfortunately this is not working and I am getting the following output:
ERROR : Unsupported document type for unmarshalling: []bson.M
Just wondering what I'm doing wrong and how to resolve this.
Any help will be highly appreciated.
Thanks in advance.
Ripul
答案1
得分: 6
将
err1 := pipe.One(&results)
改为
err1 := pipe.All(&results)
英文:
Change
err1 := pipe.One(&results)
to
err1 := pipe.All(&results)
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