presto-main/src/main/java/io/prestosql/operator/aggregation/multimapagg/LegacyGroupedMultimapAggregationState.java/LegacyGroupedMultimapAggregationState/getEntryCount
class LegacyGroupedMultimapAggregationState:    @Override
    public int getEntryCount()
    {
        return keyBlockBuilders.get(getGroupId()).getPositionCount();
    }