NPE in OpAsQuery #2883
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The example has several moving parts: @Test
public void testSubQuery01() {
test_roundTripQuery("SELECT ?z { SELECT ?x { } }");
}focuses on the subquery part. |
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I added your query to the PR but it was not failing before. The issue seems to be related to (NOT) EXISTS. I found more strange things going on (tested with the PR applied which only passes on an expr transform which otherwise might result in NPE): # TestOpAsQuery.java
@Test
public void testExists08a() {
String queryStr = """
SELECT * {
FILTER NOT EXISTS { SELECT * { ?s a ?t } LIMIT 2 }
}
""";
Query inputQuery = QueryFactory.create(queryStr);
Op op = Algebra.compile(inputQuery);
System.out.println("Original Op: " + op);
// Output looks OK to me:
// (filter (notexists
// (slice _ 2
// (bgp (triple ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?t))))
// (table unit))
Query queryFromOriginalOp = OpAsQuery.asQuery(op);
System.out.println("Query from original op: " + queryFromOriginalOp);
// Output looks OK to me - Note that an empty graph pattern was injected but that should be fine:
// SELECT * WHERE { { }
// FILTER NOT EXISTS { SELECT * WHERE { ?s a ?t } LIMIT 2 } }
Op parsedOp = SSE.parseOp(op.toString());
System.out.println("Parse op " + parsedOp);
// Output looks OK to me:
// (filter (notexists
// (slice _ 2
// (bgp (triple ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?t))))
// (table unit))
Query queryFromParsedOp = OpAsQuery.asQuery(parsedOp);
System.out.println("Query from parsed op: " + queryFromParsedOp);
// Now there is a warning and the SLICE 2 got lost
// WARN ElementTransformer :: Attempt to transform a null element - ignored
// Query from parsed op: SELECT *
// WHERE
// { { }
// FILTER NOT EXISTS { ?s a ?t }
// }
}😮 So something seems to break with the Op/Element duality in Also: @Test
public void testExists08b() {
String opStr = """
(filter (notexists
(slice _ 2
(bgp (triple ?s <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> ?t))))
(table unit)
)
""";
test_AlgebraToQuery(opStr, "SELECT * { { } FILTER NOT EXISTS { SELECT * { ?s a ?t } LIMIT 2 } }");
}gives |
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Aklakan
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The aforementioned issue #2883 (comment) should now be fixed in the proposed PR. |
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Version
5.3.0-SNAPSHOT
What happened?
The following query fails an
OpAsQueryroundtrip due to an NPE:Relevant output and stacktrace
Are you interested in making a pull request?
Yes
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