MongoDB切片查询到golang

Question

How can i write this below slice query into golang?

db.con.find({"repoid":1356485},{"contr":{$slice:[0,10]}}).pretty()

Tried with this but not working

DB.C("con").Find(bson.M{"id": ID, "contr": bson.M{"$slice": []interface{}{"$contr", offset, limit}}})

does not find anything. Any ideas?

Thank you in advance

Answer 1

With Collection.Find() you can only specify the filter. But what you have is a projection:

{"contr":{$slice:[0,10]}

Projections can be specified using Query.Select(), so this is how you can apply a $slice in projection:

var results []bson.M // Use your own type here, but this works too

err := DB.C("con").Find(bson.M{"id": ID}).Select(bson.M{
    "contr": bson.M{"$slice": []int{offset, limit}},
}).All(&results)

// handle error

Also note sure if the property you filter by is "id" or is just a typo and it should be "_id". If the latter, you may also use Collection.FindId() to query by document ID:

err := DB.C("con").FindId(ID).Select(bson.M{
    "contr": bson.M{"$slice": []int{offset, limit}},
}).All(&results)