[jira] [Commented] (JENA-495) Regression in evaluation of aggregates with trailing VALUES

["Rob Vesse (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/JENA-495?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13722849#comment-13722849 ] 

Rob Vesse commented on JENA-495:
--------------------------------

This is not a regression AFAICT merely ARQ having been updated to correctly implement the specification for trailing VALUES clauses.

>From the spec Section 18.2.4(http://www.w3.org/TR/sparql11-query/#convertGroupAggSelectExpressions):

{quote}
In this step, we process clauses on the query level in the following order:

* Grouping
* Aggregates
* HAVING
* VALUES
* Select expressions
{quote}

Note that trailing VALUES applies after the aggregation step.

In the first two queries where the VALUES block is trailing it applies after the aggregates are calculated so it is expected that the ?sum and ?count variables would have values of 0, then the VALUES are joined in hence why you get two rows.  The prior behaviour in 2.7.1 may have been correct at the time but is incorrect wrt the final state of the specification.

In the third case an inline VALUES is joined in at the point where it appears (Section 18.2.2.6), by putting it inside the WHERE clause you ensure it is processed before the aggregation stage so you get the aggregate results that you expect.
                
> Regression in evaluation of aggregates with trailing VALUES
> -----------------------------------------------------------
>
>                 Key: JENA-495
>                 URL: https://issues.apache.org/jira/browse/JENA-495
>             Project: Apache Jena
>          Issue Type: Bug
>          Components: ARQ, Jena
>    Affects Versions: Jena 2.10.1
>            Reporter: Mark Buquor
>
> {noformat}
> The following query returns {{x, 1},{x, 2}} with 2.7.1 and 2.10.1 as expected:
>  PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
>  SELECT *
>  WHERE {  }
>  VALUES ?x { 1 2 }
> The following query returns {{sum,3}} with 2.7.1. With 2.10.1, it returns no results.
>  PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
>  SELECT (SUM(?x) AS ?sum)
>  WHERE {  }
>  VALUES ?x { 1 2 }
> The following query returns {{count,2}} with 2.7.1. With 2.10.1, it returns {{count,0},{count,0}}.
>  PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
>  SELECT (COUNT(?x) AS ?count)
>  WHERE {  }
>  VALUES ?x { 1 2 }
> The queries work as expected with 2.10.1 if the VALUES is moved into the WHERE. e.g.
>  PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
>  SELECT (COUNT(?x) AS ?count)
>  WHERE { VALUES ?x { 1 2 } }
> {noformat}

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