ResultSet is closed using toStream

[des.m...@gmail.com]

Hi

In order to avoid placing large amounts of data in memory I want to be able to return my ResultSet in a stream - and I should be able to do it according to this post: https://groups.google.com/forum/#!searchin/squeryl/stream/squeryl/aZMsfikBejA/rFI59-Owte4J

But I have tried changing a query like the one below:

val results = transaction {
  from(table)(r => select(t)).toList
}

to

val results = transaction {
  from(table)(r => select(t)).toStream
}

and this causes the exception "The ResultSet is closed" once I try to access the stream:

results match {
  case h #:: t => // Causes an exception
...

Is there I way I can actually use a stream?

Thanks
Des

[Thomas Suckow]

The stream is only useable inside the transaction block.

[des.m...@gmail.com]

I used the pagination feature to provide stream type access and this way usage of the stream is not restricted to just inside a transaction block:

    implicit def pagedStreamer[T](query: => Query[T])  = new {

        def asStream(pageSize: Int): Stream[T] = next(List(), 0, pageSize)

        private def next(currentSet: List[T], offset: Int, pageSize: Int): Stream[T] = currentSet match {
            case h :: t => h #:: next(t, offset, pageSize)
            case _ =>
                transaction { query.page(offset, pageSize).toList } match {
                    case Nil => Stream.empty
                    case nextPage => next(nextPage, offset + pageSize, pageSize)
                }
        }
    }