docs: @Override
  	protected void computeOperatorSpecificDefaultEstimates(DataStatistics statistics) {
  		long card1 = getFirstPredecessorNode().getEstimatedNumRecords();
  		long card2 = getSecondPredecessorNode().getEstimatedNumRecords();
  		this.estimatedNumRecords = (card1 < 0 || card2 < 0) ? -1 : Math.max(card1, card2);
  		
  		if (this.estimatedNumRecords >= 0) {
  			float width1 = getFirstPredecessorNode().getEstimatedAvgWidthPerOutputRecord();
  			float width2 = getSecondPredecessorNode().getEstimatedAvgWidthPerOutputRecord();
  			float width = (width1 <= 0 || width2 <= 0) ? -1 : width1 + width2;
  			
  			if (width > 0) {
  				this.estimatedOutputSize = (long) (width * this.estimatedNumRecords);
  			}
  		}
  	}