W3C home > Mailing lists > Public > public-rdf-dawg-comments@w3.org > October 2006

Re: make regex optional in SPARQL

From: Steve Harris <steve.harris@garlik.com>
Date: Mon, 23 Oct 2006 13:43:54 +0100
Message-Id: <5327CDD4-D0FD-411F-9CDB-836E003A5578@garlik.com>
To: public-rdf-dawg-comments@w3.org

[sorry, replying from web interface, so no quote or in-reply-to header]

I don't think it's a real problem. My RDF store (JXT) handles  
anything up to 10 bn triples and can deal with regex queries. Just  
because it's in the spec doesn't mean you're required to use it in  
queries.

Other query forms, such as

SELECT *
WEHRE { ?v :p ?w . ?x :q ?y }

or excessive use of UNION are far more expensive on the whole, and  
have to be handled somehow.

Many regex queries can be reduced to (case insensitive) prefix  
substring matches, or simpler classes of pattern matching, and those  
that can't can be refused by the engine should the query be too  
onerous. For example by default my engine refuses to fully execute  
things like:

SELECT *
WHERE { ?x ?y ?z . FILTER(regex(str(?x), ".*foo", "i") }

as it has no indexes to bring to bear on the problem, and  
individually processing 10 billion objects is very time consuming.

- Steve
Received on Monday, 23 October 2006 12:44:54 GMT

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