presto-main/src/main/java/io/prestosql/operator/NestedLoopJoinPagesBuilder.java/NestedLoopJoinPagesBuilder/addPage
class NestedLoopJoinPagesBuilder:    public void addPage(Page page)
    {
        checkState(!finished, "NestedLoopJoinPagesBuilder is finished");

        // ignore empty pages
        if (page.getPositionCount() == 0) {
            return;
        }

        pages.add(page);
        estimatedSize += page.getRetainedSizeInBytes();
    }