Elad . wrote: > > Hi, > > I have a database with 52 columns and 7 million rows. dear Elad,
Thanks for using MonetDB. The problem you describe is known. No easy solution exists, because the front-end optimizer does not use, nor rely on table statistics to derive the best plan. A solution will emerge, but don't hold your breath regards, Martin > > The columns are Date (timestamp data type), Customer (real data > type) and a bunch of other columns that indicate values for each > customer on each date (all of these columns are of real data type). > > The 'Date' column contains 5 unique values. > > The 'Customer' column contains 1.7 million unique values. > > 1. The following query returns instantly: SELECT "CUSTOMER" FROM "TABLE". > > 2. The following query takes a long time (stopped after a few > minutes): SELECT "CUSTOMER" FROM "TABLE" GROUP BY "CUSTOMER". > > 3. The following query returns instantly: SELECT "DATE", "CUSTOMER" > FROM "TABLE" GROUP BY "DATE", "CUSTOMER". > > 4. The following query takes a long time (stopped after a few > minutes): SELECT "CUSTOMER", "DATE" from "TABLE" GROUP BY "CUSTOMER", > "DATE". > > * Note that the only difference between query 1 and query 2 are the > addition of a group by clause to query 2. > > * Note that the only difference between query 3 and query 4 are the > order of columns in the select and group by clauses. > > Is there a way to work around this? I'm really stuck. > > Thanks in advance, > > Elad > > ------------------------------------------------------------------------ > Talk to your Yahoo! Friends via Windows Live Messenger. Find Out How > <http://www.windowslive.com/explore/messenger?ocid=TXT_TAGLM_WL_messenger_yahoo_082008> > > > ------------------------------------------------------------------------ > > ------------------------------------------------------------------------- > This SF.Net email is sponsored by the Moblin Your Move Developer's challenge > Build the coolest Linux based applications with Moblin SDK & win great prizes > Grand prize is a trip for two to an Open Source event anywhere in the world > http://moblin-contest.org/redirect.php?banner_id=100&url=/ > ------------------------------------------------------------------------ > > _______________________________________________ > Monetdb-developers mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/monetdb-developers > ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Monetdb-developers mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/monetdb-developers
