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Re: LIMIT problem (Paging)

From: Richard Newman <rnewman@franz.com>
Date: Thu, 28 May 2009 10:07:24 -0700
Message-ID: <4A1EC4CC.3030204@franz.com>
To: Mirko <idonthaveenoughinformation@googlemail.com>
CC: public-sparql-dev@w3.org
>> If a store has an index on my:hasUserID (and that index happens to be 
>> in SPARQL's defined order!) then results can be generated in ordered 
>> sequence.
> 
> Do you mean, I can assume to get "ordered" results without explicit 
> "ORDER BY" in the query, given the appropriate index? independent from 
> the database implementation? In my current setting (Sesame with 
> NativeStore - default index spoc, posc) this is not the case.

You can't assume anything about result order without including an ORDER BY clause for each column you care about. I was 
simply commenting on the relative expense of a query: an implementation with the right predicate-specific index (and a 
sufficiently smart planner) would -- in principle -- be able to generate ordered results more cheaply than one without 
such an index, simply by walking that index first. You still need to tell it to do so.

Thanks,

-R
Received on Thursday, 28 May 2009 17:08:05 GMT

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