[elephant-devel] Querying for objects on two slots

[Ian Eslick]

Right now they're 32 bits by convention, but I'd like them to be 64- 
bits on a 64-bit machine eventually so far I don't think we're in  
danger of blowing out 32 bits of oids - you can compact OID values by  
doing a migration.  Actually it wouldn't be hard to replace this with  
a 'find next unused oid' given that we have an oid table and the  
beginnings of a GC algorithm now.

Ian

On Jan 14, 2009, at 3:07 PM, Yarek Kowalik 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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> >
>
>
>
> --
> Robert Synnott
> http://myblog.rsynnott.com
> MSN: rsynnott at gmail.com
> Jabber: rsynnott at gmail.com
>
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