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https://issues.apache.org/jira/browse/JENA-1275?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15822841#comment-15822841
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Andy Seaborne edited comment on JENA-1275 at 1/14/17 6:44 PM:
--------------------------------------------------------------
Simpler example:
{noformat}
public static void main(String... args) {
String z2 = "(filter (notexists (bgp (triple ?z ?p ?x) )) (bgp (?x ?a
?z)) )";
Op op2 = SSE.parseOp(z2);
List<Var> vars = Collections.singletonList(Var.alloc("x"));
Op op3 = Rename.renameVars(op2, vars);
System.out.println(op3);
}
{noformat}
Output:
{noformat}
(filter (notexists (bgp (triple ?//z ?//p ?x)))
(bgp (triple ?x ?/a ?/z)))
{noformat}
because
{{ApplyTransformVisitor.visit(OpFilter)}} transforms the filters of the
OpFilter then the process calls {{NodeTransformOp}} which does it again.
The double project is significant only because if it were one level the code
knows rewriting at all is not necessary.
was (Author: andy.seaborne):
Simpler example:
{noformat}
public static void main(String... args) {
String z = "(project (?A) (project (?x) (filter (notexists (bgp (triple
?z ?p ?x) )) (table unit) )))";
Op op = SSE.parseOp(z);
System.out.println("::Algebra::");
System.out.println(op);
Op op1 = Algebra.optimize(op);
System.out.println("::Optimized::");
System.out.println(op1);
}
{noformat}
Output:
{noformat}
::Algebra::
(project (?A)
(project (?x)
(filter (notexists (bgp (triple ?z ?p ?x)))
(table unit))))
::Optimized::
(project (?A)
(project (?x)
(filter (notexists (bgp (triple ?//z ?//p ?x)))
(table unit))))
{noformat}
It look like:
* it is the {{(project (project ... ))}}
* not related to quads
* not related to group even though group has an implicit projection
> TransformScopeRename does the wrong thing with FILTER NOT EXISTS
> ----------------------------------------------------------------
>
> Key: JENA-1275
> URL: https://issues.apache.org/jira/browse/JENA-1275
> Project: Apache Jena
> Issue Type: Bug
> Components: ARQ
> Affects Versions: Jena 3.1.1
> Reporter: Rob Vesse
> Assignee: Andy Seaborne
>
> I have produced the following minimal query from an originally much larger
> query. When the optimise is applied to this it incorrectly double renames the
> variables inside of the {{FILTER NOT EXISTS}} clause leading to incorrect
> algebra.
> Query:
> {noformat}
> SELECT ?triangles ?openTriplets
> {
> {
> #subQ2: calculate #open-triplets
> SELECT (COUNT(?x) as ?openTriplets)
> WHERE {
> ?x ?a ?y .
> ?y ?b ?z .
> FILTER NOT EXISTS {?z ?c ?x}
> }
> }
> }
> {noformat}
> Output:
> {noformat}
> (project (?triangles ?openTriplets)
> (project (?openTriplets)
> (extend ((?openTriplets ?/.0))
> (group () ((?/.0 (count ?/x)))
> (filter (notexists
> (quadpattern (quad <urn:x-arq:DefaultGraphNode> ?//z ?//c
> ?//x)))
> (quadpattern
> (quad <urn:x-arq:DefaultGraphNode> ?/x ?/a ?/y)
> (quad <urn:x-arq:DefaultGraphNode> ?/y ?/b ?/z)
> ))))))
> {noformat}
> Note that we apply the quad transformation prior to applying the optimiser.
> Strangely enough I cannot reproduce the problem using pure Jena command line
> tools i.e. {{qparse}} although I note from the code that it applies quad
> transformation after applying optimisation. This suggests that it is a bug in
> how TransformScopeRename applies to quad form algebra.
> I can reproduce it with a unit test like so:
> {noformat}
> @Test
> public void filter_not_exists_scoping_03() {
> //@formatter:off
> Op orig = SSE.parseOp(StrUtils.strjoinNL("(project (?triangles
> ?openTriplets)",
> " (project (?openTriplets)",
> " (extend ((?openTriplets ?.0))",
> " (group () ((?.0 (count ?x)))",
> " (filter (notexists",
> " (quadpattern (quad
> <urn:x-arq:DefaultGraphNode> ?z ?c ?x)))",
> " (quadpattern",
> " (quad
> <urn:x-arq:DefaultGraphNode> ?x ?a ?y)",
> " (quad
> <urn:x-arq:DefaultGraphNode> ?y ?b ?z)",
> " ))))))"));
> Op expected = SSE.parseOp(StrUtils.strjoinNL("(project (?triangles
> ?openTriplets)",
> " (project (?openTriplets)",
> " (extend ((?openTriplets ?/.0))",
> " (group () ((?/.0 (count ?/x)))",
> " (filter (notexists",
> " (quadpattern (quad
> <urn:x-arq:DefaultGraphNode> ?/z ?/c ?/x)))",
> " (quadpattern",
> " (quad <urn:x-arq:DefaultGraphNode> ?/x ?/a ?/y)",
> " (quad <urn:x-arq:DefaultGraphNode> ?/y ?/b ?/z)",
> " ))))))"));
> //@formatter:on
>
> Op transformed = TransformScopeRename.transform(orig);
>
> Assert.assertEquals(transformed, expected);
> }
>
> @Test
> public void filter_not_exists_scoping_04() {
> //@formatter:off
> Op orig = SSE.parseOp(StrUtils.strjoinNL(
> " (project (?openTriplets)",
> " (extend ((?openTriplets ?.0))",
> " (group () ((?.0 (count ?x)))",
> " (filter (notexists",
> " (quadpattern (quad
> <urn:x-arq:DefaultGraphNode> ?z ?c ?x)))",
> " (quadpattern",
> " (quad
> <urn:x-arq:DefaultGraphNode> ?x ?a ?y)",
> " (quad
> <urn:x-arq:DefaultGraphNode> ?y ?b ?z)",
> " )))))"));
> Op expected = SSE.parseOp(StrUtils.strjoinNL(
> " (project (?openTriplets)",
> " (extend ((?openTriplets ?.0))",
> " (group () ((?.0 (count ?x)))",
> " (filter (notexists",
> " (quadpattern (quad
> <urn:x-arq:DefaultGraphNode> ?z ?c ?x)))",
> " (quadpattern",
> " (quad <urn:x-arq:DefaultGraphNode> ?x ?a ?y)",
> " (quad <urn:x-arq:DefaultGraphNode> ?y ?b ?z)",
> " )))))"));
> //@formatter:on
>
> Op transformed = TransformScopeRename.transform(orig);
>
> Assert.assertEquals(transformed, expected);
> }
> {noformat}
> The first test fails while the second passes. This implies that you need 2
> levels of projection to hit the bug.
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