presto-main/src/main/java/io/prestosql/operator/SortedPositionLinks.java/PositionComparator/compare
class PositionComparator:        @Override
        public int compare(int leftPosition, int rightPosition)
        {
            long leftPageAddress = addresses.getLong(leftPosition);
            int leftBlockIndex = decodeSliceIndex(leftPageAddress);
            int leftBlockPosition = decodePosition(leftPageAddress);

            long rightPageAddress = addresses.getLong(rightPosition);
            int rightBlockIndex = decodeSliceIndex(rightPageAddress);
            int rightBlockPosition = decodePosition(rightPageAddress);

            return pagesHashStrategy.compareSortChannelPositions(leftBlockIndex, leftBlockPosition, rightBlockIndex, rightBlockPosition);
        }