"SELECT DISTINCT * " produces duplicates when blank nodes are used the graph
pattern
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Key: JENA-229
URL: https://issues.apache.org/jira/browse/JENA-229
Project: Apache Jena
Issue Type: Bug
Components: ARQ
Affects Versions: ARQ 2.9.0, ARQ 2.9.1
Reporter: Stephen Allen
Priority: Minor
When using a blank node in the graph pattern of a query, using "select distinct
*" can result in duplicate rows. There is a similar issue with "select reduced
*"
Steps to reproduce:
1) Load the "books" database [1]
2) Add an additional statement [2]
3) Run the following query:
PREFIX books: <http://example.org/book/>
PREFIX dc: <http://purl.org/dc/elements/1.1/>
select distinct *
where {
?book dc:title ?title .
?book dc:creator [] .
}
You see that you get a duplicate result for book5.
If you change the query to:
PREFIX books: <http://example.org/book/>
PREFIX dc: <http://purl.org/dc/elements/1.1/>
select distinct ?book ?title
where {
?book dc:title ?title .
?book dc:creator [] .
}
You do not get duplicates.
[1]
http://svn.apache.org/repos/asf/incubator/jena/Jena2/Fuseki/trunk/Data/books.ttl
[2] <http://example.org/book/book5> <http://purl.org/dc/elements/1.1/creator>
"Sir Example" .
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