Hello! Only btree, no hash indexes?
2014-03-06 13:46 GMT-03:00 Sergei Golubchik <[email protected]>: > 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 > -- Roberto Spadim SPAEmpresarial Eng. Automação e Controle
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