Text search (lucene) with tdbquery

Samur Araujo

2016-12-22 12:03:29 UTC

Thank you Andy, this makes things clear.

I understood the best way is to use Fuseki engine and access the data via
sparql service.

It would be idea to have the tdbquery command working with the indexes as
well.

Best,
Samur

Post by Andy Seaborne

Hi all, Is it possible to use tdbquery for textsearch?
I have configured, loaded and index the data using tdbloader and
jena.textindexer.
However, when I use tdbquery to query the database it seems to ignore the
lucene index.
tdbquery --desc textsearch.ttl --query search.rq

By default, the class files for jena-text will not be available to the
command. Did you not get some kind of warning? (which version are you
using?)
However, the main issue is that theer are two datasets in the assembler
file. "tdbquery --desc" will look for the TDB dataset.
I think it needs some coding to run a text backed query. Use
TextDatasetFactory.create(filename) to build from the assembler.
(Maybe there is a better way someone can point out - I have used jena-text
in a while).
Andy

Do I need to provide any extra configuration? Do I need to compile jena
with special features?

No - but the TDB command line tools are not sufficient.

@prefix : <http://localhost/jena_example/#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix tdb: <http://jena.hpl.hp.com/2008/tdb#> .
@prefix ja: <http://jena.hpl.hp.com/2005/11/Assembler#> .
@prefix text: <http://jena.apache.org/text#> .
## Example of a TDB dataset and text index
## Initialize TDB
[] ja:loadClass "org.apache.jena.tdb.TDB" .
tdb:DatasetTDB rdfs:subClassOf ja:RDFDataset .
tdb:GraphTDB rdfs:subClassOf ja:Model .
## Initialize text query
[] ja:loadClass "org.apache.jena.query.text.TextQuery" .
# A TextDataset is a regular dataset with a text index.
text:TextDataset rdfs:subClassOf ja:RDFDataset .
# Lucene index
text:TextIndexLucene rdfs:subClassOf text:TextIndex .
# Solr index
text:TextIndexSolr rdfs:subClassOf text:TextIndex .
## ---------------------------------------------------------------
## This URI must be fixed - it's used to assemble the text dataset.
:text_dataset rdf:type text:TextDataset ;
text:dataset <#dataset> ;
text:index <#indexLucene> ;
.
# A TDB datset used for RDF storage
<#dataset> rdf:type tdb:DatasetTDB ;
tdb:location "DB2" ;
tdb:unionDefaultGraph true ; # Optional
.
# Text index description
<#indexLucene> a text:TextIndexLucene ;
text:directory <file:Lucene2> ;
##text:directory "mem" ;
text:entityMap <#entMap> ;
.
# Mapping in the index
# URI stored in field "uri"
# rdfs:label is mapped to field "text"
<#entMap> a text:EntityMap ;
text:entityField "uri" ;
text:defaultField "text" ;
text:map (
[ text:field "text" ; text:predicate rdfs:label ]
) .

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