[elephant-devel] Querying for objects on two slots

[Yarek Kowalik]

Correction (missing single quotes):

(format t "~8,'0X ~8,0'X" slot-a-val slot-b-val)



On Wed, Jan 14, 2009 at 12:07 PM, Yarek Kowalik <yarek.kowalik at gmail.com>wrote:

> Out of curiosity, the OIDs in elephant are they 32 bit integers or 64?  I'm
> running on Ubuntu-64/SBCL-64.
>
> I'm thinking that my 'query' slot vale would be generated something like
> this (for 32 bit values):
>
> (format t "~8,0X ~8,0X" slot-a-val slot-b-val)
>
> Yarek
>
>
> On Tue, Jan 13, 2009 at 5:51 PM, Robert Synnott <rsynnott at gmail.com>wrote:
>
>> 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.kowalik at 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 <killerstorm at 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 at common-lisp.net
>> >> http://common-lisp.net/mailman/listinfo/elephant-devel
>> >
>> >
>> > _______________________________________________
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>> > elephant-devel at common-lisp.net
>> > http://common-lisp.net/mailman/listinfo/elephant-devel
>> >
>>
>>
>>
>> --
>> Robert Synnott
>> http://myblog.rsynnott.com
>> MSN: rsynnott at gmail.com
>> Jabber: rsynnott at gmail.com
>>
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>>
>
>
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