[jira] [Comment Edited] (JENA-2335) Query -> Algebra -> Query not equivalent in case of a BIND not in the result vars

["Andy Seaborne (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/JENA-2335?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17560904#comment-17560904 ] 

Andy Seaborne edited comment on JENA-2335 at 6/30/22 8:11 AM:
--------------------------------------------------------------

Hi [~jmkeil]

This looks like https://github.com/apache/jena/issues/1369

The output from the development code is currently:

{noformat}
SELECT  ?a (?c AS ?d)
WHERE
  { ?a  <http://example.org/p>  ?b
    BIND(?b AS ?c)
  }
{noformat}

Slightly different format but the invariant of "same algebra" is maintained:

{code:java}
    public static void main(String...a) {
        String qs = "SELECT ?a ?d WHERE { ?a <http://example.org/p> ?b . BIND(?b AS ?c) BIND(?c AS ?d) }";
        Query q1 = QueryFactory.create(qs);
        Op op1 = Algebra.compile(q1);
        Query q2 = OpAsQuery.asQuery(op1);
        Op op2 = Algebra.compile(q2);

        System.out.println(q1);
        System.out.println(q2);
        System.out.println("Algebra equals: "+op1.equals(op2));
    }
{code}
Tests for 1369:
[sparql/algebra/TestOpAsQuery.java|https://github.com/apache/jena/blob/7c0b20742a8fac15da14f256debbbbbeeeb40eaa/jena-arq/src/test/java/org/apache/jena/sparql/algebra/TestOpAsQuery.java#L74]

If it is the case, that this is already, I will add your test case to {{TestOpAsQuery}}.



was (Author: andy.seaborne):
Hi [~jmkeil]

This looks like https://github.com/apache/jena/issues/1369

The output from the development code is currently:

{noformat}
SELECT  ?a (?c AS ?d)
WHERE
  { ?a  <http://example.org/p>  ?b
    BIND(?b AS ?c)
  }
{noformat}

and the invariant of "same algebra" is maintained:

{code:java}
    public static void main(String...a) {
        String qs = "SELECT ?a ?d WHERE { ?a <http://example.org/p> ?b . BIND(?b AS ?c) BIND(?c AS ?d) }";
        Query q1 = QueryFactory.create(qs);
        Op op1 = Algebra.compile(q1);
        Query q2 = OpAsQuery.asQuery(op1);
        Op op2 = Algebra.compile(q2);

        System.out.println(q1);
        System.out.println(q2);
        System.out.println("Algebra equals: "+op1.equals(op2));
    }
{code}
Tests for 1369:
[sparql/algebra/TestOpAsQuery.java|https://github.com/apache/jena/blob/7c0b20742a8fac15da14f256debbbbbeeeb40eaa/jena-arq/src/test/java/org/apache/jena/sparql/algebra/TestOpAsQuery.java#L74]



> Query -> Algebra -> Query not equivalent in case of a BIND not in the result vars
> ---------------------------------------------------------------------------------
>
>                 Key: JENA-2335
>                 URL: https://issues.apache.org/jira/browse/JENA-2335
>             Project: Apache Jena
>          Issue Type: Bug
>          Components: ARQ, Optimizer
>    Affects Versions: Jena 4.5.0
>            Reporter: Jan Martin Keil
>            Priority: Major
>
> Converting a query into algebra and back results in a not equivalent query, if the query contains a BIND clause thous variable is not part of the result variables, but other variables depend on it. Minimal example:
> {code:java}
> import static org.junit.jupiter.api.Assertions.assertTrue;
> import org.apache.jena.query.QueryFactory;
> import org.apache.jena.sparql.algebra.AlgebraGenerator;
> import org.apache.jena.sparql.algebra.OpAsQuery;
> import org.junit.jupiter.api.Test;
> public class OpTest {
> 	@Test
> 	public void retainVariables() {
> 		String sparqlStrBeforOp = "SELECT ?a ?d WHERE { ?a <http://example.org/p> ?b . BIND(?b AS ?c) BIND(?c AS ?d) }";
> 		String sparqlStrAfterOp = OpAsQuery.asQuery(new AlgebraGenerator().compile(QueryFactory.create(sparqlStrBeforOp))).toString();
> 		System.out.println(sparqlStrAfterOp);
> 		assertTrue(sparqlStrAfterOp.contains("(?b AS ?c)"));
> 	}
> }
> {code}
> This results in the following query:
> {code:sql}
> SELECT  ?a (?c AS ?d)
> WHERE
>   { ?a  <http://example.org/p>  ?b }
> {code}
> Use case: I do the conversion back and forth to remove not needed result variables of a given query on algebra level, which is not possible on queries directly.



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