Make users.u_id UNIQUE for use as a FK in user_teams_membership#1587
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cpeel
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Jun 3, 2026
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I confirmed on PROD that all values of users.u_id are unique as a sanity check.
cpeel
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Jun 4, 2026
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Actually, I tried running this on TEST and got the following error. MySQL doesn't like that we're trying to drop the index on an auto column:
cpeel@test:~/u-cpeel-dp/SETUP/upgrade/25 (unique-u-id)$ php 20260603_make_users_u_id_unique.php
Making u_id INDEX in users UNIQUE..
ALTER TABLE users
DROP INDEX u_id;
<p class='error'>
Incorrect table definition; there can be only one auto column and it must be defined as a key
</p><pre>
PHP Fatal error: Uncaught mysqli_sql_exception: Incorrect table definition; there can be only one auto column and it must be defined as a key in /home/cpeel/u-cpeel-dp/SETUP/upgrade/25/20260603_make_users_u_id_unique.php:17
Stack trace:
#0 /home/cpeel/u-cpeel-dp/SETUP/upgrade/25/20260603_make_users_u_id_unique.php(17): mysqli_query()
#1 {main}
thrown in /home/cpeel/u-cpeel-dp/SETUP/upgrade/25/20260603_make_users_u_id_unique.php on line 17
Wonder how we get out of this pickle?
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Turns out you can chain a list of 'alter specifications' in a single SQL command... |
MySQL 8.0 InnoDB allows foreign keys to ref an indexed but not unique column. This is deprecated by default in MySQL 8.4 (in Ubuntu 26.04) and produces the error `Failed to add the foreign key constraint. Missing unique key for constraint 'user_teams_membership_ibfk_1' in the referenced table 'users'` See https://dev.mysql.com/doc/refman/8.4/en/server-system-variables.html#sysvar_restrict_fk_on_non_standard_key
cpeel
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Jun 4, 2026
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MySQL 8.0 InnoDB allows foreign keys to ref an indexed but not unique column.
This is deprecated by default in MySQL 8.4 (in Ubuntu 26.04) and produces the error
Failed to add the foreign key constraint. Missing unique key for constraint 'user_teams_membership_ibfk_1' in the referenced table 'users'See https://dev.mysql.com/doc/refman/8.4/en/server-system-variables.html#sysvar_restrict_fk_on_non_standard_key
(Found when trying to run
SETUP/install_db.phpon an Ubuntu 26.04 VM)