}
private Row createEmptyOutput() {
assert noGroupBy() : "shouldn't be creating null output row when I have a grouping";
ValuesHolderRow outputRow = newOutputRow();
for (int i = 0; i < outputRow.rowType().nFields(); ++i) {
pAggrs.get(i).emptyValue(outputRow.valueAt(i));
}
return outputRow;
}