On Tue, May 12, 2009 at 06:19:49PM -0500, Mayank Maheshwari wrote:

Hi,

I was trying out selection queries with varying selectivity factors on a 1 million tuple relation. The selectivity factors for predicates were 0.1%, 1% and 10% of the entries in the column and the data type of the column is int. What I'm seeing is that the execution time increases with selectivity factors going from 0.1% to 1% to 10%. I'm not sure why this is happening though, considering its a column-store system. Should this be attributed to increase in CPU time or disk I/Os or any other factor? What my understanding of column-store systems is that the execution time should remain constant for varying selectivity factors for the same column. Any help would be appreciated.

Range selections on non-sorted data are linear in both the input size, the result length (selectivity) and the result width (projectivity). Stefan

Thanks

Mayank

Mayank Maheshwari mayank@cs.wisc.edu

------------------------------------------------------------------------------ The NEW KODAK i700 Series Scanners deliver under ANY circumstances! Your production scanning environment may not be a perfect world - but thanks to Kodak, there's a perfect scanner to get the job done! With the NEW KODAK i700 Series Scanner you'll get full speed at 300 dpi even with all image processing features enabled. http://p.sf.net/sfu/kodak-com _______________________________________________ MonetDB-users mailing list MonetDB-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/monetdb-users

-- | Dr. Stefan Manegold | mailto:Stefan.Manegold@cwi.nl | | CWI, P.O.Box 94079 | http://www.cwi.nl/~manegold/ | | 1090 GB Amsterdam | Tel.: +31 (20) 592-4212 | | The Netherlands | Fax : +31 (20) 592-4312 |