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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.


Received on Thursday, 28 May 2009 17:08:05 UTC

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