presto-main/src/main/java/io/prestosql/operator/project/MergingPageOutput.java/MergingPageOutput/process
class MergingPageOutput:    private void process(Page page)
    {
        requireNonNull(page, "page is null");

        // avoid memory copying for pages that are big enough
        if (page.getPositionCount() >= minRowCount || page.getSizeInBytes() >= minPageSizeInBytes) {
            flush();
            outputQueue.add(page);
            return;
        }

        buffer(page);
    }