presto-elasticsearch/src/main/java/io/prestosql/elasticsearch/ElasticsearchPageSource.java/ElasticsearchPageSource/computeNext
class ElasticsearchPageSource:        @Override
        protected SearchHit computeNext()
        {
            if (scrollId == null) {
                long start = System.nanoTime();
                SearchResponse response = first.get();
                readTimeNanos += System.nanoTime() - start;
                reset(response);
            }
            else if (currentPosition == searchHits.getHits().length) {
                long start = System.nanoTime();
                SearchResponse response = client.nextPage(scrollId);
                readTimeNanos += System.nanoTime() - start;
                reset(response);
            }

            if (currentPosition == searchHits.getHits().length) {
                return endOfData();
            }

            SearchHit hit = searchHits.getAt(currentPosition);
            currentPosition++;

            return hit;
        }