presto-main/src/main/java/io/prestosql/operator/PagesRTreeIndex.java/PagesRTreeIndex/getRadius
class PagesRTreeIndex:    private double getRadius(int joinPosition)
    {
        long joinAddress = addresses.getLong(joinPosition);
        int blockIndex = decodeSliceIndex(joinAddress);
        int blockPosition = decodePosition(joinAddress);

        return DOUBLE.getDouble(channels.get(radiusChannel).get(blockIndex), blockPosition);
    }