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 >
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