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

        return createArrayBlockInternal(
                position + getOffsetBase(),
                length,
                getValueIsNull(),
                getOffsets(),
                getRawElementBlock());
    }