Store and retrieve items in order using BoltDB

Question

I am using BoltDB with Golang and want to store and then retrieve my items in the order they were placed into my database.

I am setting items using

func (r *Bolt) Set(key string, value []byte) error {
    return r.Client.Update(func(tx *bolt.Tx) error {
        b := tx.Bucket([]byte(r.bucket))
        return b.Put([]byte(key), value)
    })
}

And then I attempt to get all items and return the first 10 using a limit.

// GetAll will fetch the latest n record from Bolt, up to the limit supplied.
func (r *Bolt) GetAll(limit int) ([][]byte, error) {
    var results [][]byte

    if err := r.Client.View(func(tx *bolt.Tx) error {
        b := tx.Bucket([]byte(r.bucket))
        if b == nil {
            return fmt.Errorf("bucket %s not found", r.bucket)
        }

        // Set the cursor to the last key in the bucket
        c := b.Cursor()
        lastKey, _ := c.Last()

        // Iterate over the data in descending order, starting from the last key
        for k, v := c.Seek(lastKey); k != nil; k, v = c.Prev() {
            results = append(results, v)

            // Return if we have collected 50 items
            if len(results) >= limit {
                break
            }
        }

        return nil
    }); err != nil {
        return nil, err
    }

    return results, nil
}

If I use the following as keys test1, test2, test3, test4` in my database they always seem to be retrieved in random order.

Is there a way I can guarantee the order of items from BoltDB?

I have a createdAt time field on the data I'm saving, I'm thinking I could potentially use that but it would mean I'd have to retrieve all items and then sort.

Answer 1

You can. You are having the logical error in your code. You should use the c.First() method instead c.Seek() or c.Last() to do that according to documentation