PseudoTest.scala

val scanner = accumulo.connector.createScanner(tableName, new Authorizations())
val iteratorSetting = new IteratorSetting(Int.MaxValue, classOf[RowCounterIterator])
scanner.addScanIterator(iteratorSetting)
val iterator = scanner.iterator()
iterator.hasNext shouldEqual true
val entry = iterator.next()
entry.getValue.get().length shouldEqual 0
println(entry)
LongByteCodec.decode(entry.getKey.getRowData.toArray) shouldEqual daySubscriberProfiles.size
scanner.close()

RowCounterIterator.scala

import org.apache.accumulo.core.data.{ Key, Value }
import org.apache.accumulo.core.iterators.{ IteratorEnvironment, SortedKeyValueIterator, WrappingIterator }

/**
 * An `Iterator` that counts the element of the wrapping iterator and returns one
 * key-value with the counter
 */
class RowCounterIterator extends WrappingIterator {

  /** Build a `RowCounterIterator` from a `IteratorEnviroment` and another `RowCounterIterator` */
  def this(env: IteratorEnvironment, that: RowCounterIterator) {
    this()
    setSource(that.getSource.deepCopy(env))
    counter = that.counter
    nextHasBeenCalled = that.nextHasBeenCalled
    hasNext = that.hasNext
  }

  override def deepCopy(env: IteratorEnvironment): RowCounterIterator = new RowCounterIterator(env, this)

  /** Number of elements found */
  private[iterator] var counter = 0L

  /** `true` if `next()` has been called, `false` otherwise */
  private[iterator] var nextHasBeenCalled = false

  /** `true` if `next()` has been called zero or one time, `false` otherwise */
  private[iterator] var hasNext = true

  override def hasTop(): Boolean = this.hasNext

  /** @return a `Key` with the row set to this `counter` */
  override def getTopKey(): Key = new Key(LongByteCodec.encode(this.counter), ByteCodec.emptyByteArray,
    ByteCodec.emptyByteArray, ByteCodec.emptyByteArray, Long.MaxValue)

  /** @return an empty `Value` */
  override def getTopValue(): Value = new Value()

  override def next(): Unit = {
    if (this.nextHasBeenCalled) {
      this.hasNext = false
    } else {
      while (super.hasTop() && !super.getTopKey.isDeleted) {
        this.counter += 1L
        super.next()
      }
      this.nextHasBeenCalled = true
    }
  }
}