Hi, Federico! On Mar 23, Federico Razzoli wrote: > Hello list > > I found out that EXPLAIN SELECT aggregate_func() FROM connect_table returns a > "rows" value which is much greater than the rows in the table. For example: > > MariaDB [test]> SELECT COUNT(*) FROM t; > +----------+ > | COUNT(*) | > +----------+ > | 1000000 | > +----------+ > 1 row in set (0.49 sec) > > MariaDB [test]> EXPLAIN SELECT COUNT(*) FROM t; > +------+-------------+-------+------+---------------+------+---------+------+---------+-------+ > | id | select_type | table | type | possible_keys | key | key_len | ref | > rows | Extra | > +------+-------------+-------+------+---------------+------+---------+------+---------+-------+ > | 1 | SIMPLE | t | ALL | NULL | NULL | NULL | NULL | > 7783705 | | > +------+-------------+-------+------+---------------+------+---------+------+---------+-------+ > > So, my question is: is there any difference in the output of EXPLAIN > with CONNECT? Is CONNECT really reading 7.8 millions rows in a table > with only 1 million rows?
No, most probably it means that CONNECT estimates in this case are way off. Could you show a complete test case for this? 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
