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Even though user invisible columns are supposed to have default values, this works:
MariaDB [test]> create or replace table t1 (pk int auto_increment primary key invisible, i int);
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# Query OK, 0 rows affected (0.16 sec)
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MariaDB [test]> alter table t1 modify pk int invisible;
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# Query OK, 0 rows affected (0.80 sec)
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# Records: 0 Duplicates: 0 Warnings: 0
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The resulting table structure is this:
MariaDB [test]> show create table t1;
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+-------+------------------------------------------------------------------------------------------------------------------------------------------------+
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| Table | Create Table |
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+-------+------------------------------------------------------------------------------------------------------------------------------------------------+
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| t1 | CREATE TABLE `t1` (
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`pk` int(11) NOT NULL INVISIBLE,
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`i` int(11) DEFAULT NULL,
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PRIMARY KEY (`pk`)
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) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
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+-------+------------------------------------------------------------------------------------------------------------------------------------------------+
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1 row in set (0.01 sec)
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If you try to execute it, it produces an error:
MariaDB [test]> drop table t1;
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Query OK, 0 rows affected (0.07 sec)
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MariaDB [test]> CREATE TABLE `t1` (
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-> `pk` int(11) NOT NULL INVISIBLE,
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-> `i` int(11) DEFAULT NULL,
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-> PRIMARY KEY (`pk`)
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-> ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
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ERROR 4106 (HY000): Invisible column `pk` must have a default value
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My guess is that ALTER in the initial pair of commands should be rejected.
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