presto-main/src/main/java/io/prestosql/operator/SimplePagesHashStrategy.java/SimplePagesHashStrategy/isPositionNull
class SimplePagesHashStrategy:    @Override
    public boolean isPositionNull(int blockIndex, int blockPosition)
    {
        for (int hashChannel : hashChannels) {
            if (isChannelPositionNull(hashChannel, blockIndex, blockPosition)) {
                return true;
            }
        }
        return false;
    }