Hi, Anshu! On Jun 11, Anshu Avinash wrote: > Hi serg, > > I have attached the updated diff. I'm still unable to observe the effect > introduced by the cost factors. Maybe I just need to study the usage of > scan_time() and read_time() in greater detail.
Ok, see one suggestion below. If that won't help - push your changes to github, I'll try myself. > diff --git a/mysql-test/r/costmodel.result b/mysql-test/r/costmodel.result > new file mode 100644 > index 0000000..6668758 > --- /dev/null > +++ b/mysql-test/r/costmodel.result > @@ -0,0 +1,20 @@ > +DROP TABLE IF EXISTS t1; > +CREATE TABLE t1 (a int auto_increment primary key, b int); > +INSERT INTO t1(b) values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11),(12), > +(13),(14),(15),(16),(17),(18),(19),(20),(21),(22),(23),(24),(25); > +EXPLAIN > +SELECT * FROM t1 > +WHERE a > 21; > +id select_type table type possible_keys key key_len ref > rows Extra > +1 SIMPLE t1 range PRIMARY PRIMARY 4 NULL 5 Using > index condition > +use mysql; > +UPDATE optimizer_cost_factors > +SET const_value=2.0 > +WHERE const_name='SCAN_TIME_FACTOR'; > +use test; > +EXPLAIN > +SELECT * FROM t1 > +WHERE a > 21; > +id select_type table type possible_keys key key_len ref > rows Extra > +1 SIMPLE t1 range PRIMARY PRIMARY 4 NULL 5 Using > index condition > +DROP TABLE t1; See? Your first EXPLAIN already shows type=range. And then you increase the cost of the table scan. Of course, nothing can happen anymore. Try to make the first explain to show type=ALL (which means table scan), then increase the cost of the table scan and see how optimizer will switch to type=range. Regards, Sergei _______________________________________________ Mailing list: https://launchpad.net/~maria-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~maria-developers More help : https://help.launchpad.net/ListHelp
