presto-spi/src/main/java/io/prestosql/spi/block/LongArrayBlockBuilder.java/LongArrayBlockBuilder/getRegion
class LongArrayBlockBuilder:    @Override
    public Block getRegion(int positionOffset, int length)
    {
        checkValidRegion(getPositionCount(), positionOffset, length);

        if (!hasNonNullValue) {
            return new RunLengthEncodedBlock(NULL_VALUE_BLOCK, length);
        }
        return new LongArrayBlock(positionOffset, length, hasNullValue ? valueIsNull : null, values);
    }