presto-main/src/main/java/io/prestosql/operator/window/PagesWindowIndex.java/PagesWindowIndex/PagesWindowIndex
class PagesWindowIndex:    public PagesWindowIndex(PagesIndex pagesIndex, int start, int end)
    {
        requireNonNull(pagesIndex, "pagesIndex is null");
        checkPositionIndex(start, pagesIndex.getPositionCount(), "start");
        checkPositionIndex(end, pagesIndex.getPositionCount(), "end");
        checkArgument(start < end, "start must be before end");

        this.pagesIndex = pagesIndex;
        this.start = start;
        this.size = end - start;
    }