Hi, Erik! On Apr 20, Erik Cederstrand wrote: > > CREATE TABLE `t1` ( `i` int(11) NOT NULL, `j` int(11) NOT NULL, `l` > int(11) NOT NULL, `m` int(11) DEFAULT NULL, PRIMARY KEY > (`i`,`j`,`l`)); > > CREATE TABLE `t2` ( `i` int(11) NOT NULL, `k` int(11) DEFAULT NULL, > PRIMARY KEY (`i`)) ENGINE=InnoDB DEFAULT CHARSET=utf8; > > The problematic query is this: > SELECT DISTINCT t2.i, t2.k, t1.j, t1.l, t1.m FROM t2 LEFT JOIN t1 > ON t2.i=t1.i WHERE t2.k < 123; > > The query is slow because the DISTINCT clause forces the query to use > a temporary table. Removing DISTINCT makes the query 100x faster. > ... > it could also be argued that MariaDB should be smart enough to detect > that the DISTINCT is unnecessary and ignore it (should I create a bug > report for that?).
Yes, please, do report it! On the first glance this looks like a rather simple optimization. Regards, Sergei Chief Architect MariaDB and [email protected] _______________________________________________ Mailing list: https://launchpad.net/~maria-discuss Post to : [email protected] Unsubscribe : https://launchpad.net/~maria-discuss More help : https://help.launchpad.net/ListHelp
