Hello Rob,
LIKE operator in SPARQL clones SQL LIKE so you should use "Queen%Elizabeth"
string as the right argument of LIKE, not aa regex.
If you realy need to use regex then use regex :) It's PCRE-based so you may
make the pattern case-insensitive by (?i) option, e.g.
regex(?mystring, "(?i)Queen Elizabeth") . The proper support for third
argument of REGEX will be added in next version.
In any case, indexes are not used by REGEX due to the nature of regular
expressions. If you're looking for names that consists of words, consider
using of free-text index as described in
http://docs.openlinksw.com/virtuoso/freetext.html (if you haven't tried
free-text of Virtuoso before) and
http://docs.openlinksw.com/virtuoso/rdfsparqlrulefulltext.html (RDF-specific
details)
Best Regards,
Ivan Mikhailov,
OpenLink Software
----- Original Message -----
From: "robl" <r...@monkeyhelper.com>
To: <virtuoso-users@lists.sourceforge.net>
Sent: Monday, April 21, 2008 8:40 PM
Subject: [Virtuoso-users] DBpedia and Virtuoso SPARQL Query
Hi,
I'm currently working with the latest DBpedia dataset in Virtuoso OS
Edition (5.06). I'm trying to do the equivalent of a SQL LIKE using
SPARQL on a resource subject. So in SQL this would have been something
like :
SELECT * FROM pages WHERE page_title LIKE "Queen%Elizabeth"
This would perform a case insensitive match on Queen(anything)Elizabeth
(at least in mySQL).
I have tried the following in my virtuoso instance :
SELECT ?subject ?predicate ?object WHERE {
?subject ?predicate ?object.
FILTER(?subject like "^http://dbpedia.org/resource/Queen.*Elizabeth$";)
}
SELECT ?subject ?predicate ?object WHERE {
?subject ?predicate ?object.
FILTER regex(?subject,
"^http://dbpedia.org/resource/Queen.*Elizabeth$";, "i")
}
These both take well over a minute to return (and the first doesn't seem
to be case insensitive), which isn't acceptable for my particular
application.
Is there quick way to do what I want ? Are there any indexes I could
apply to improve things (I have already created the indexes specified at
http://www.openlinksw.com/dataspace/kide...@openlinksw.com/weblog/kide...@openlinksw.com's%20BLOG%20%5B127%5D/1298)
?
Or do I need to create a conventional SQL table of resource names and
then do a SQL LIKE query on those ?
Thanks,
Rob
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