Scylla gocqlx how to implement pagination similar to a cursor - go

Question

I'm using Scylla to save parties created by a users. The method below returns a list of parties created by a user. I currently return all parties without allowing pagination, but I'm trying to implement Pagination for the method below but I still don't quite understand how pagination is handled with Scylla.
My guess would be that a cursor can be passed to a query. Based on this example it looks like the PageState can be used to pass something similar to a cursor.
I would appreciate a short explanation what PageState is and if I should use it to accomplish token based pagination. It would also be great if an example could be provided that shows how a new PageState can be returned to the client and used to fetch a new page on a second request.
func (pq *partyQuery) GetByUser(ctx context.Context, uId string) ([]datastruct.Party, error) {
var result []datastruct.Party
stmt, names := qb.
Select(TABLE_NAME).
Where(qb.Eq("user_id")).
ToCql()
err := pq.sess.
Query(stmt, names).
BindMap((qb.M{"user_id": uId})).
PageSize(10).
Iter().
Select(&result)
if err != nil {
log.Println(err)
return []datastruct.Party{}, errors.New("no parties found")
}
return result, nil
}
Thanks in advance and I appreciate your time.
Edit
For anybody interested, this is how I transformed my function to allow paging:
func (pq *partyQuery) GetByUser(ctx context.Context, uId string, page []byte) (result []datastruct.Party, nextPage []byte, err error) {
stmt, names := qb.
Select(TABLE_NAME).
Where(qb.Eq("user_id")).
ToCql()
q := pq.sess.
Query(stmt, names).
BindMap((qb.M{"user_id": uId}))
defer q.Release()
q.PageState(page)
q.PageSize(10)
iter := q.Iter()
err = iter.Select(&result)
if err != nil {
log.Println(err)
return []datastruct.Party{}, nil, errors.New("no parties found")
}
return result, iter.PageState(), nil
}

Answer 1

Hi gocqlx author here.
Please take a look at this example https://github.com/scylladb/gocqlx/blob/25d81de30ebcdfa02d3d849b518fc57b839e4399/example_test.go#L482
getUserVideos := func(userID int, page []byte) (userVideos []Video, nextPage []byte, err error) {
q := videoTable.SelectQuery(session).Bind(userID)
defer q.Release()
q.PageState(page)
q.PageSize(itemsPerPage)
iter := q.Iter()
return userVideos, iter.PageState(), iter.Select(&userVideos)
}
You need to send page state to caller.