I don't believe the Postmodern backend, at least, allows search by conses. If you want sensible (ordered) results with a and b if a and/or b are integers, by the way, you should zero-pad them; otherwise, say, '1 2' comes after '1 12', which is probably not what you want Rob
2009/1/14 Yarek Kowalik <yarek.kowa...@gmail.com>: > When serializing tuples, is the string representation best: You suggest > using (format t "~A ~A" a b) - is that efficient enough? what about doing > (cons a b) = is there a way to index and search for conses? Any other ideas? > > Yarek > > On Tue, Jan 6, 2009 at 5:17 AM, Alex Mizrahi <killerst...@newmail.ru> wrote: >> >> YK> Is this a reasonable way of finding an object of type >> YK> 'my-class that matches on values val-a and val-b for slots a and b? >> >> yep, it is reasonable if you have relatively low number of objects >> in returned by (get-instances-by-value 'my-class 'slot-b val-b) query. >> if number of objects is significant and you get a slowdown because >> of this, you might want to optimize this. a trivial thing is to try it >> symmertrically with slot-a -- whatever returns less objects is better. >> less trivial optimizations would be to work on lower-level -- via >> map-inverted-index (to avoid allocating whole list but instead test >> objects >> one by one) or even cursor API (this way you can retrieve oids rather >> than objects, which should be faster, and also iterating both indices at >> once might be a significant benefit if values are not uniformly >> distributed). >> >> but the most optimal way doing this in case of high number of objects >> in both slot-a and slot-b queries would be building and using multi-column >> index. unfortunately, Elephant does not help you with it -- either you'll >> have >> to serialize slot tuples into a string (e.g (format nil "~a_~a" slot-a >> slot-b)), >> or reorganize your data to use a custom index structure (like btree of >> btrees). >> >> there are also backend-specific considerations. for postmodern >> >> (intersection (get-instances-by-value 'my-class 'slot-b val-b) >> (get-instances-by-value 'my-class 'slot-a val-a)) >> >> would be much faster then testing objects one by one, for BDB -- i doubt >> so. >> >> LP> Use MAP-CLASS, this will considerably speed up the query. >> >> how is that? using at least one index is much better than using no index >> at >> all. >> >> >> >> >> _______________________________________________ >> elephant-devel site list >> elephant-devel@common-lisp.net >> http://common-lisp.net/mailman/listinfo/elephant-devel > > > _______________________________________________ > elephant-devel site list > elephant-devel@common-lisp.net > http://common-lisp.net/mailman/listinfo/elephant-devel > -- Robert Synnott http://myblog.rsynnott.com MSN: rsynn...@gmail.com Jabber: rsynn...@gmail.com _______________________________________________ elephant-devel site list elephant-devel@common-lisp.net http://common-lisp.net/mailman/listinfo/elephant-devel