presto-geospatial/src/main/java/io/prestosql/plugin/geospatial/SpatialPartitioningStateFactory.java/GroupedSpatialPartitioningState/setSamples
class GroupedSpatialPartitioningState:        @Override
        public void setSamples(List<Rectangle> samples)
        {
            List<Rectangle> currentSamples = this.samples.get(groupId);
            if (currentSamples != null) {
                samplesCount -= currentSamples.size();
            }
            samplesCount += samples.size();
            this.samples.set(groupId, samples);
        }