row = new Object[aggregations.length];
this.collectExpressions = collectExpressions;
aggregationCollectors = new AggregationCollector[aggregations.length];
for (int i = 0; i < aggregationCollectors.length; i++) {
aggregationCollectors[i] = new AggregationCollector(
aggregations[i].symbol(),
aggregations[i].function(),
aggregations[i].inputs()
);
// startCollect creates the aggregationState. In case of the AggregationProjector