Question

I’m trying to build a list page like the one in the “Computers” sample. My environment is Play 2.0 and PostrgreSQL 9.0

I have the following method in my User object:

 def list(page: Int = 0, pageSize: Int = 10, orderBy: Int = 1, filter: String = "%"): Page[User] = {
    val offset = pageSize * page
    val mode = if (orderBy > 0) "ASC NULLS FIRST" else "DESC NULLS LAST"

    Logger.debug("Users.list with params: page[%d] pageSize[%d] orderBy[%d] filter[%s] order[%s]".format(page, pageSize, orderBy, filter, mode))

    DB.withConnection {
      implicit connection =>

        val users = SQL(
          """
            select * from publisher
            where name ilike {filter}
            order by {orderBy} %s
            limit {pageSize} offset {offset}
          """.format(mode)
        ).on(
          'pageSize -> pageSize,
          'offset -> offset,
          'filter -> filter,
          'orderBy -> scala.math.abs(orderBy)
        ).as(User.simple *)

        val totalRows = SQL(
          """
            select count(*) from publisher
            where name like {filter}
          """
        ).on(
          'filter -> filter
        ).as(scalar[Long].single)

        Page(users, page, offset, totalRows)
    }

  }

Doesn’t matter which value of ‘orderBy’ I provide, the order is always based on id of the entities.

The query generated by Anorm is valid PostgreSQL and it works fine when running it against the database directly. But it seems like if Anorm parser was ignoring the order in which the results are returned, and instead returns a list ordered by ‘id’.

I’ve even tried to simplify the query to a "select * from publisher order by 2 ASC/DESC", but nothing is fixed, the ordering is ignored by Anorm on return.

Any suggestion on how to solve this issue?

Answer 1

Thanks to Guillaume on the mailing list of Play I found a workaround.

All placeholders work except the one in order by. The worse part is that when you follow the logs, the driver generates the correct query and PostgreSQL is receiving it. I’m not sure what’s the deal, very confusing, but if I remove that placeholder, it just works.

Depressing 🙁

I solved it like this:

val users = SQL(
  """
    select * from publisher
    where name ilike {filter}
    order by %d %s
    limit {pageSize} offset {offset}
  """.format(scala.math.abs(orderBy), mode)
).on(
  'pageSize -> pageSize,
  'offset -> offset,
  'filter -> filter
).as(User.simple *)

Now you’ll be screaming “SQL INJECTION”. Relax. Although it may be possible somehow, orderBy is an integer (which we turn into abs value for more safety). If you try to call the controller that provides orderBy with a string, Play returns a 404 error. So only integers are allowed. And if there is no column corresponding to the given integer, the order by is ignored. So, not ideal, but not so bad.