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https://issues.apache.org/jira/browse/JENA-1254?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Andy Seaborne closed JENA-1254.
-------------------------------
Resolution: Fixed
Closed after a week.
> GROUP_CONCAT returns nothing when concatenating unbound and bound values.
> -------------------------------------------------------------------------
>
> Key: JENA-1254
> URL: https://issues.apache.org/jira/browse/JENA-1254
> Project: Apache Jena
> Issue Type: Bug
> Components: ARQ
> Affects Versions: Jena 3.1.0
> Reporter: Yev Bronshteyn
> Attachments: c_spdxtest_5530.rdf
>
>
> The following two queries have the same triples in their {{where}} clauses in
> different order. While it is expected that the first query will return only
> one solution and the second query - multiple (per
> https://wiki.blazegraph.com/wiki/index.php/SPARQL_Order_Matters), it is *not*
> expected that the optional {{copyrightTexts}} value will appear in the result
> of the first query, but not in the corresponding solution in the result of
> the second query.
> {code}
> prefix spdx: <http://spdx.org/rdf/terms#>
> prefix rdf:<http://www.w3.org/1999/02/22-rdf-syntax-ns#>
> prefix doap:<http://usefulinc.com/ns/doap#>
>
> select
> (group_concat(distinct(?licText);separator="\n\n") as ?licTexts)
> (group_concat(?copyrightText;separator="\n\n") as ?copyrightTexts)
> ?name
> where {
> optional {
> ?elem spdx:copyrightText ?copyrightText .
> filter (isLiteral(?copyrightText))
> } .
> {
> # And the name
> {?elem spdx:name ?name}
> union
> {
> ?elem spdx:artifactOf ?artifact .
> ?artifact doap:name ?name
> }
> }.
> }
> group by ?name
> {code}
> And
> {code}
> prefix spdx: <http://spdx.org/rdf/terms#>
> prefix rdf:<http://www.w3.org/1999/02/22-rdf-syntax-ns#>
> prefix doap:<http://usefulinc.com/ns/doap#>
>
> select
> (group_concat(distinct(?licText);separator="\n\n") as ?licTexts)
> (group_concat(?copyrightText;separator="\n\n") as ?copyrightTexts)
> ?name
> where {
> {
> # And the name
> {?elem spdx:name ?name}
> union
> {
> ?elem spdx:artifactOf ?artifact .
> ?artifact doap:name ?name
> }
> }.
> optional {
> ?elem spdx:copyrightText ?copyrightText .
> filter (isLiteral(?copyrightText))
> } .
> }
> group by ?name
> {code}
> The issue seems to be that with the second query, GROUP_CONCAT has to
> concatenate the bound value of ?copyrightText with unbound values. Changing
> the second query to unconditionally bind a value to ?copyrightText eliminates
> the behavior.
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