Treating an SQL ResultSet like a Scala Stream

Question

When I query a database and receive a (forward-only, read-only) ResultSet back, the ResultSet acts like a list of database rows.

I am trying to find some way to treat this ResultSet like a Scala Stream. This will allow such operations as filter, map, etc., while not consuming large amounts of RAM.

I implemented a tail-recursive method to extract the individual items, but this requires that all items be in memory at the same time, a problem if the ResultSet is very large:

// Iterate through the result set and gather all of the String values into a list // then return that list @tailrec def loop(resultSet: ResultSet,          accumulator: List[String] = List()): List[String] = {   if (!resultSet.next) accumulator.reverse   else {     val value = resultSet.getString(1)     loop(resultSet, value +: accumulator)   } } 

Answer 1

I didn't test it, but why wouldn't it work?

new Iterator[String] {   def hasNext = resultSet.next()   def next() = resultSet.getString(1) }.toStream