code: protected void computeCostEstimates(long childOutputTupleCountEstimate,
                                          DatabaseEstimates estimates,
                                          ScalarValueHints[] paramHints)
      {
          m_estimatedOutputTupleCount = childOutputTupleCountEstimate;
          m_estimatedProcessedTupleCount = childOutputTupleCountEstimate;
      }
docs: Given the number of tuples expected as input to this node, compute an estimate
  of the number of tuples read/processed and the number of tuples output.
  This will be called by
  {@see AbstractPlanNode#computeEstimatesRecursively(PlanStatistics, Cluster, Database, DatabaseEstimates, ScalarValueHints[])}.