Aggregation Pipeline Stage - $bucketAuto

Build the $bucketAuto stage through the aggregation pipeline stage builder aggregation.NewStageBuilder using the method BucketAuto.

Suppose we want to divide users into 4 age groups and perform some basic statistics on each group:

type User struct {
	mongox.Model `bson:"inline"`
	Name         string `bson:"name"`
	Age          int    `bson:"age"`
}

// mongo.Pipeline{bson.D{bson.E{Key:"$bucketAuto", Value:bson.D{bson.E{Key:"groupBy", Value:"$age"}, bson.E{Key:"buckets", Value:4}, bson.E{Key:"output", Value:bson.D{bson.E{Key:"count", Value:bson.D{bson.E{Key:"$sum", Value:1}}}, bson.E{Key:"averageAge", Value:bson.D{bson.E{Key:"$avg", Value:"$age"}}}, bson.E{Key:"names", Value:bson.D{bson.E{Key:"$push", Value:"$name"}}}}}}}}}
// [
//  {
//    "$bucketAuto": {
//      "groupBy": "$age", // Specifies the field for grouping
//      "buckets": 4, // Specifies the number of buckets to create
//      "output": {
//        "count": { "$sum": 1 }, // Number of documents in each bucket
//        "averageAge": { "$avg": "$age" }, // Average age in each bucket
//        "names": { "$push": "$name" } // Collects the names of all users in each bucket
//      }
//    }
//  }
//]
aggregation.NewStageBuilder().BucketAuto(
    "$age",
    4,
    &types.BucketAutoOptions{
        Output: aggregation.NewBuilder().
            Sum("count", 1).
            Avg("averageAge", "$age").
            Push("names", "$name").Build(),
    },
).Build()

The BucketAuto method takes three parameters: groupBy any, buckets int, and opt *types.BucketAutoOptions. For advanced settings, you can pass the opt parameter, setting the output parameters to define the format of the output documents, or set the granularity parameter to specify the granularity of the buckets.