MongoDB in Go (golang) with mgo: how to use logical operators to query?

Question

I would like to run the following query in golang using mgo in a pipeline.

{"key1" : 1,
 "$or" : [{"key2" : 2}, {"key3" : 2}]}

I have looked everywhere, but I cannot find an example like this. I have tried many different combinations, for example:

...
pipeline := []bson.M{
                     bson.M{    "$match" :  bson.M{ "key1" : 1,  
                                                   "$or" : bson.M{ "key2" : 2, "key3" : 2},
                     }
                     ...
            }

which compiles correctly, does not find anything. Any ideas?

Thank you in advance

Hustings

Answer 1

Your mongo query can be translated to the following:

pipeline := bson.D{
    {"key1", 1},
    {"$or", []interface{}{
        bson.D{{"key2", 2}},
        bson.D{{"key3", 2}},
    }},
}

The query should be equivalent to the following in the mongo console:

db.mycollection.find({"key1" : 1, "$or" : [{"key2" : 2}, {"key3" : 2}]})

If you'd rather wish to use unordered maps, bson.M, it would be like this:

pipeline := bson.M{
    "key1": 1,
    "$or": []interface{}{
        bson.M{"key2": 2},
        bson.M{"key3": 2},
    },
}

Iceskate

Welcome! You missed the array/slice, so the key was []interface{} – Iceskate

I copy pasted your bson.D example and I get "exception: A pipeline stage specification object must contain exactly one field." – Buehrer

@Buehrer Are you using the query in a Find or Pipe? The error is a mongodb one, but I haven't played so much with building aggregation pipelines, so I can't tell you right away how to fix it. Sorry. – Iceskate

pipe := collection.Pipe(pipeline) if error := pipe.All(&res); error != nil { t.Fatal(error) } – Buehrer

Hey, why we cannot using bson.D for []interface{}? I guess it's the same thing, right? I've tried it, but It seems the query is not working as expected. Any reason? – Skewer

Oh sorry, stupid question. bson.D is not []interface{}, bson.A does. If we're using bson.D instead of []interface{} (since bson.D is []bson.E, can't have bson.D or bson.M inside bson.D), then the structure would be different, hence the query will not working. – Skewer

Answer 2

go lang Mongo db Or query

findQuery := bson.M{"key1" : 1}
orQuery := []bson.M{}
orQuery := append(orQuery, bson.M{"key2" : 2}, bson.M{"key3" : 2})

findquery["$or"] = orQuery
result := []interface{}
err := mongo.DB.C("collectionName").find(findQuery).All(&result)

Colquitt