MongoDB Go driver Query Samples

Samples in Golang for MongoDb driver - Various query examples

The original CRUD examples are taken from here: https://dev.to/eduardohitek/mongodb-golang-driver-tutorial-49e5

It was very hard to found bson samples for Golang, so during time I started to gather and create this sample collection.

Query examples:

Retrieve by int field "age" greater than and equal to 30

filter := bson.M{"age": bson. M{"$gte":30}}

Retrieve by int field "age" less than and equal to 30

filter = bson.M{"age": bson. M{"$lte":30}}

Retrieve by string field "name" field equal to "Mazdak" (Case sensitive)

filter = bson.M{"name": "Mazdak"}

Retrieve by string field "name" equal to "Mazdak" (Case In-sensitive) - Regex way

name := "^mazdak"
regex := bson.M{"$regex": primitive.Regex{Pattern: name, Options : "i"}}

filter = bson.M{"name": regex}

Like operator. Retrieve by string field "name"

name = "mazdak"
regex = bson.M{"$regex": primitive.Regex{Pattern: name, Options : "i"}}

filter = bson.M{"name": regex}

Get documents when a specific does not exists

filter = bson.M{"age": bson. M{"$exists": false}}

And operator: "age" greater/equal to "30" and "name" equal to "Anai"

filter = bson.M{
	"$and": []bson.M{
		bson.M{"name": "Anai"},
		bson. M{"age": bson. M{"$gte":30}},
	},
}

Or operator: "age" greater/equal to 30 or "name" equal to "Anai"

filter = bson.M{
	"$or": []bson.M{
		bson.M{"name": "Anai"},
		bson. M{"age": bson. M{"$gte":30}},
	},
}

And-Or operator together 1. "age" less than 10 OR greater than 30, AND "signed" false

filter = bson.M{
	"$and": []bson.M{
			bson.M{
				"$or": []bson.M{
					bson.M{"age": bson. M{"$lt":10}},
					bson.M{"age": bson. M{"$gt":30}},
				},
			},
			bson.M{"signed": false},
		},
	}

And-Or operator together 2. "age" more than 30 AND "alias" equal "Mazoo" , OR "signed" false

filter = bson.M{
	"$or": []bson.M{
		bson.M{
			"$and": []bson.M{
				bson.M{"alias": "Mazoo"},
				bson.M{"age": bson. M{"$gt":30}},
			},
		},
		bson.M{"signed": false},
	},
}

Get one Record by ObjectId

docID, _ := primitive.ObjectIDFromHex("5de30185e4fabe4778f0ffdf")

hero := ReturnOneHero(c, bson.M{"_id" : docID})

Get documents created from yesterday

filter = bson. M{"createdDate": bson. M{"$gte": time.Now().AddDate(0,0,-1)}}

Get documents updated since last 5 days based on timestamp type field

filter = bson. M{"lastUpdate": bson. M{"$gte": primitive.Timestamp{T:uint32(time.Now().AddDate(0,0,-10).Unix())} }}

Some Piplines:

Stage 1: Join to city document. Stage 2: Select specific fields with $project Stage 3: Group on city field and count number of each city on the document.

stage1 := bson.M{
	"$lookup": bson.M{
		"from": "cities",
		"localField": "cityId",
		"foreignField": "_id",
		"as" : "city",
	},
}

stage2 := bson.M{
	"$project": bson.M{
		"_id": 0,
		"name": 1,
		"age": 1,
		"city": bson.M{ "$arrayElemAt" : []interface{}{"$city.name",0} },
	},
}

stage3 := bson.M{
	"$group": bson.M{
		"_id" : "$city",
		"count": bson.M{
			"$sum": 1,
		},
	},}

Gain the same result with bson.UnmarshalExtJSON. With this technique, we can directly take guery from MongoDb Compass (Json stirng), and this method will convert it to proper format.

pipeline := make([]bson.M, 0)
err := bson.UnmarshalExtJSON([]byte(strings.TrimSpace(`
	   [{
		"$lookup": {
					"from" : "cities",
					"localField": "cityId",
					"foreignField": "_id",
					"as" : "city"
				}}
		, {
		"$project": {
		  "_id": 0,
		  "name": 1,
		  "age": 1,
		  "city": { "$arrayElemAt" : ["$city.name", 0]}
		}},
		{
		"$group": {
		  "_id" : "$city",
		  "count": {
			"$sum": 1
		  }
		}}]
		`)), true, &pipeline)