On Mon, Mar 08, 2010 at 08:02:35PM +0530, anshul gangwar wrote:

hello ,        Is the cost model used at compile time or at runtime for estimation of cardinalities

I don't know which is "*the* cost model" that you refer to, but as we tried to explain before the current open source version of MonetDB/XQuery does not do any cardinality estimation for XQuery optimization, neither at compile time nor at runtime. The various operations in the MonetDB kernel do some "ad hoc" cardinality estimation based on the properties of their inputs or on sampling. See the code in MonetDB/src/gdk/ for details. Stefan -- | 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) 592-4199 |