[JENA-1172] blank nodes can break jena-text

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Jena 3.0.1
• Fix Version/s: Jena 3.1.0
• Component/s: Text
• Assignee: Osma Suominen
• Reporter: Osma Suominen
• Created: 02/May/16 07:27
• Updated: 14/May/16 09:51
• Resolved: 03/May/16 10:25

Description

Data with blank node subjects can break the jena-text index.

For this example I use a typical jena-text configuration which indexes rdfs:label. Then I add this triple:

_:b0 <http://www.w3.org/2000/01/rdf-schema#label> "blank" .

There is no error (though I remember seeing WARNINGs in other situations like this) and the triple gets indexed.

When I later execute this query:

PREFIX text: <http://jena.apache.org/text#>
SELECT ?s { ?s text:query 'blank' }

I get this error:

10:22:38 WARN  [5] RC = 500 : java.lang.UnsupportedOperationException: 3ed87b7f14f612ef53788d889f6410d6 is not a URI node
org.apache.jena.ext.com.google.common.util.concurrent.UncheckedExecutionException: java.lang.UnsupportedOperationException: 3ed87b7f14f612ef53788d889f6410d6 is not a URI node
	at org.apache.jena.ext.com.google.common.cache.LocalCache$Segment.get(LocalCache.java:2203)
	at org.apache.jena.ext.com.google.common.cache.LocalCache.get(LocalCache.java:3937)
	at org.apache.jena.ext.com.google.common.cache.LocalCache$LocalManualCache.get(LocalCache.java:4739)
	at org.apache.jena.atlas.lib.cache.CacheGuava.getOrFill(CacheGuava.java:58)
	at org.apache.jena.query.text.TextQueryPF.query(TextQueryPF.java:291)
	at org.apache.jena.query.text.TextQueryPF.variableSubject(TextQueryPF.java:229)
	at org.apache.jena.query.text.TextQueryPF.exec(TextQueryPF.java:198)
	at org.apache.jena.sparql.pfunction.PropertyFunctionBase$RepeatApplyIteratorPF.nextStage(PropertyFunctionBase.java:106)

Note that this happens any time the jena-text query happens to match a blank node subject. So a single triple with a blank node subject can "taint" the whole index. This is what happens with LCSH, which for whatever reason happens to contain a few hundred blank nodes that have a skos:prefLabel property (among almost 8M triples that generally use URIs for everything).