presto-spi/src/main/java/io/prestosql/spi/type/BooleanType.java/BooleanType/getObjectValue
class BooleanType:    @Override
    public Object getObjectValue(ConnectorSession session, Block block, int position)
    {
        if (block.isNull(position)) {
            return null;
        }

        return block.getByte(position, 0) != 0;
    }