TYPO3 Core

yes this would be very nice but does have a hug impact. Hopefully will be adressed in V 5.0

Isn't is possible to keep a modern shadow table:

So we create a MM table, just like the relations have to be in modern extensions. Then we attach a function to the update/insert hook from fe_users. When updating a record the group-assignment will be saved komma seperated in the fe_user.usergroup field but also in the MM table so we can use the values in a normal way, with a nice query.

It also works without REGEX

SELECT * FROM `be_users` WHERE FIND_IN_SET('###groupid###', usergroup)>0

thx for the pointer. IMO this is still not a real solution though.

it exists an dbal safe function in class.t3lib_db.php for this purpose.

see function listQuery

Resolved, won't fix.

This comma-separated-list of ID's concept is found for several relations throughout the core. I don't expect it to be replaced soon, even if it's not optimal from a database point of view.

For now I resolve this issue with "won't fix" until someone comes up with a working concept (including backwards compatibility) not breaking too much. Feel free to work on this.

Furthermore a be / fe user is usually only member of a small set of group, so we usually don't search an id in a huge list, which is not a perfect, but a practical approach. Extensions still can use real mm relations, though.