如何使用正式的mongo-go-driver驱动程序过滤mongo文档中的字段 [英] How to filter fields from a mongo document with the official mongo-go-driver
问题描述
如何使用mongo-go-driver过滤字段. 使用findopt.Projection进行了尝试,但没有成功.
How can I filter fields with the mongo-go-driver. Tried it with findopt.Projection but no success.
type fields struct {
_id int16
}
s := bson.NewDocument()
filter := bson.NewDocument(bson.EC.ObjectID("_id", starterId))
var opts []findopt.One
opts = append(opts, findopt.Projection(fields{
_id: 0,
}))
staCon.collection.FindOne(nil, filter, opts...).Decode(s)
最后,我要取消显示字段"_id".但是文件没有改变.
In the end, I want to suppress the field "_id". But the documents didn't change.
推荐答案
As the mongo-go driver evolved, it is possible to specify a projection using a simple bson.M
like this:
options.FindOne().SetProjection(bson.M{"_id": 0})
原始答案(旧)如下.
之所以对您不起作用,是因为未导出字段fields._id
,因此,其他任何程序包都无法访问它(只有声明程序包).
The reason why it doesn't work for you is because the field fields._id
is unexported, and as such, no other package can access it (only the declaring package).
您必须使用导出的字段名称(以大写字母开头),例如ID
,并使用结构标签像这样将其映射到MongoDB _id
字段:
You must use a field name that is exported (starts with an uppercase latter), e.g. ID
, and use struct tags to map it to the MongoDB _id
field like this:
type fields struct {
ID int `bson:"_id"`
}
现在要使用投影执行查询:
And now to perform a query using a projection:
projection := fields{
ID: 0,
}
result := staCon.collection.FindOne(
nil, filter, options.FindOne().SetProjection(projection)).Decode(s)
请注意,您也可以使用 bson.Document
作为投影,您不需要自己的struct类型.例如.以下内容相同:
Note that you may also use a bson.Document
as the projection, you don't need your own struct type. E.g. the following does the same:
projection := bson.NewDocument(
bson.EC.Int32("_id", 0),
)
result := staCon.collection.FindOne(
nil, filter, options.FindOne().SetProjection(projection)).Decode(s)
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