Hi, pslawek83! On Feb 17, pslawek83 wrote: > Hi Guys, > any comments on this issue? It seems that partial unique indexes can't be > used in joins. > https://mariadb.atlassian.net/browse/MDEV-5663
Please, show EXPLAIN EXTENDED (and SHOW WARNINGS after it) for this query of yours. > * Why the server is treating same indexes differently depends on if > they're UNIQUE or not It doesn't, there're almost no differences between UNIQUE and non-unique indexes from the optimizer point of view. Optimizer knows that for a unique index there can be at most one matching row (if all index parts are known and are NOT NULL), for non-unique indexes there can be more. That's basically the only difference. > * That's probably not optimizer issue, as we can't FORCE the index You cannot force the index if it is not applicable at all. > * What's internal difference between unique and non-unique index (eg. > memory / file representation / data structure) none. > * What each index type is suitable for, considering query optimization > (as there's no data i was able to find on topic) Aria only supports BTREE indexes anyway. Regards, Sergei _______________________________________________ Mailing list: https://launchpad.net/~maria-discuss Post to : [email protected] Unsubscribe : https://launchpad.net/~maria-discuss More help : https://help.launchpad.net/ListHelp
