Hi, Does MonetDB split a single query plan over multiple CPU cores when its possible? (maybe the DataFlow optimizer?) For example, the following query could be executed by all cores in parallel: SELECT field1,SUM(field2) FROM Table1 GROUP BY field1 When i tried to see if it does, i got some weird results: (I am running MonetDB on Windows, on a quad core machine) When I set '--set gdk_nr_threads=1', queries never seem to use more than 25%. (seems logical since only one CPU core is being deployed) When I set '--set gdk_nr_threads=2', queries use up to 50% CPU, but the query is ~15% slower. When I set '--set gdk_nr_threads=4', queries use up to 98% CPU, but the query is take twice as long as with 1 thread. So, my initial assumption that more CPU utilization (more cores over the same query) will result faster query results (where applicable) is wrong. Can it be something specific to the windows platform? or maybe single query execution over multiple cores doesn't work without a specific optimizer flag enabled?... or maybe is it just a bug... Thanks. -- View this message in context: http://old.nabble.com/Multiple-core-usage-on-Windows-tp27002955p27002955.htm... Sent from the monetdb-users mailing list archive at Nabble.com.