Hi all,
I am currently using the LuceneSail on top of a DirectTypeHierarchyInferencer,
ForwardChainingRDFSInferencer and a MemoryStore.
When using the following query, the LuceSail is obviously already working
somehow, since the queries are roughly twice as fast as before. Still not the
real performance gain I was expecting from using Lucene (side note: the Strings
are in fact only short text snippets of usually no more than 30 characters).
----
SELECT entity, name, type
FROM {entity} rdfs:label {name} rdf:type {type}
WHERE name LIKE "*search this*" IGNORE CASE
----
The LuceneSail homepage
(http://dev.nepomuk.semanticdesktop.org/wiki/LuceneSail) introduces a different
query format for using LuceneSail, so I was using this instead to see what
happens. I changed the query to look like this then:
----
PREFIX search:<http://www.openrdf.org/contrib/lucenesail#>
SELECT ?entity ?name ?type WHERE {
?entity search:matches ?match ;
rdf:type ?type .
?match search:query "*search this*" . }
----
I only changed from SERQL to SPARQL because SPARQL was used in the example as
well. With this, the query is being executed correctly (meaning no Exceptions
or anything) but then, there are never any results returned and the query
execution is blazingly fast (which leads me to the conclusion it is in fact not
executed as expected).
So am I missing something there or what might be the reason? Another to me
unexpected behaviour is that, when using a wildcard character at the beginning
of a search string, I get the following error message. Why can I not use a
wildcard at the beginning here? Doesn't make any sense to me.
----
org.openrdf.sail.lucene.LuceneQueryIterator - There was a problem evaluating
query '*search this*' for property 'null!
org.apache.lucene.queryParser.ParseException: Cannot parse '*search this*': '*'
or '?' not allowed as first character in WildcardQuery
----
Thanks a lot in advance,
Dennis
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