Unable to sort by date in FindOne: GO Mongo driver

Working with Data Drivers
2

Hi @Frank_Martin , thanks for the question! I’ve put together the following in attempts to reproduce your use case:

package main

import (
	"context"
	"fmt"
	"log"
	"time"

	"go.mongodb.org/mongo-driver/bson"
	"go.mongodb.org/mongo-driver/bson/primitive"
	"go.mongodb.org/mongo-driver/mongo"
	"go.mongodb.org/mongo-driver/mongo/options"
)

type Source struct {
	Crawl     bool
	Processed primitive.DateTime `bson:"processed"`
}

func main() {
	opts := options.Client().ApplyURI("mongodb://localhost:27017")
	client, err := mongo.Connect(context.Background(), opts)
	if err != nil {
		panic(err)
	}

	defer func() { _ = client.Disconnect(context.Background()) }()

	// Insert some data to query.
	coll := client.Database("testdb").Collection("coll")
	coll.InsertOne(context.Background(), Source{
		Crawl:     true,
		Processed: primitive.NewDateTimeFromTime(time.Now()),
	})

	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
	defer cancel()

	find := bson.D{{"crawl", true}}
	findopts := options.FindOne().SetSort(bson.D{{"processed", 1}})

	var source *Source
	err = coll.FindOne(ctx, find, findopts).Decode(&source)

	if err != nil {
		log.Print(err)
	}

	fmt.Println("processed: ", source.Processed)
}

The output is as I would expect:

pocessed:  1707260939662

The wire message that the Go Driver sends to the server is also as-expected:

{"find": "coll","filter": {"crawl": true},"limit": {"$numberLong":"1"},"singleBatch": true,"sort": {"processed": {"$numberInt":"1"}},"lsid": {"id": {"$binary":{"base64":"QRygb0e4QgivzS9BSeyAJw==","subType":"04"}}},"$clusterTime": {"clusterTime": {"$timestamp":{"t":1707261056,"i":1}},"signature": {"hash": {"$binary":{"base64":"AAAAAAAAAAAAAAAAAAAAAAAAAAA=","subType":"00"}},"keyId": {"$numberLong":"0"}}},"$db": "testdb"}

I have a few questions

  1. Are you certain that the data you are querying has a datetime value for every source record’s processed field? You can check this with the following: db.<your coll>.aggregate([{ $group: { _id: { $type: "$processed" } } }]) . It’s worth noting that the server will sort data with string type before date and timestamp, you can see the specific rules here.

  2. If the processed data type is uniform, what version of the Go Driver are you seeing this behavior?

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