[jira] [Created] (TINKERPOP-2606) Neo4j-Gremlin could not order vertex/edge without specified property

["Liwei Liu (Jira)" <ji...@apache.org>]

Liwei Liu created TINKERPOP-2606:
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             Summary: Neo4j-Gremlin could not order vertex/edge without specified property
                 Key: TINKERPOP-2606
                 URL: https://issues.apache.org/jira/browse/TINKERPOP-2606
             Project: TinkerPop
          Issue Type: Bug
          Components: neo4j
    Affects Versions: 3.4.10
         Environment: Tinkerpop Version : 3.4.10
Neo4j Version : 3.5.27
OS : CentOS8
Storage Backend: in-memory
            Reporter: Liwei Liu


h2. Neo4j-Gremlin could not order vertex/edge without specified property
h3. Environment

Tinkerpop Version : 3.4.10

Neo4j Version : 3.5.27 

OS : CentOS8

Storage Backend: in-memory 

Data size: 100 vertices, 200 edges 
h4. Bug description

 We expect to get the vertexes/edges ordered by their ID using gremlin _order_ query without specified property like {{"g.V()/E().order().by(asc/desc)"}} in Neo4j-Gremlin, as we can get the result by the same query in JanusGraph.
h4. Current behavior

 An exception was thrown:
{code:java}
java.util.concurrent.ExecutionException: org.apache.tinkerpop.gremlin.driver.exception.ResponseException: org.apache.tinkerpop.gremlin.neo4j.structure.Neo4jVertex cannot be cast to java.lang.Comparablejava.util.concurrent.ExecutionException: org.apache.tinkerpop.gremlin.driver.exception.ResponseException: org.apache.tinkerpop.gremlin.neo4j.structure.Neo4jVertex cannot be cast to java.lang.Comparable at java.util.concurrent.CompletableFuture.reportGet(CompletableFuture.java:357) at java.util.concurrent.CompletableFuture.get(CompletableFuture.java:1908) at org.gdbtesting.validation.ValidateNeo4jOrderAsc.main(ValidateNeo4jOrderAsc.java:30)Caused by: org.apache.tinkerpop.gremlin.driver.exception.ResponseException: org.apache.tinkerpop.gremlin.neo4j.structure.Neo4jVertex cannot be cast to java.lang.Comparable
{code}
h3. Reproduce
{code:java}
GraphTraversalSource g = connection.getG();
g.E().drop().iterate();
g.V().drop().iterate();
try {
    Vertex v1 = g.addV().property("price",3).next();
    Vertex v2 = g.addV().property("price",4).next();
    Vertex v3 = g.addV().property("price",5).next();
    Vertex v4 = g.addV().property("price",6).next();    
    String query = "g.V().order().by(asc)";
    System.out.println("query: " + query);
    try{
         List<Result> results;
         results = connection.getClient().submit(query).all().get();
         for (Result r : results) {             System.out.println(r);          }
        }catch(Exception e){
             e.printStackTrace();
        }     } catch (Exception e) {
          e.printStackTrace();
} finally {
     System.exit(0);
}
{code}
We could successfully run the order() step with specified property in Neo4j-Gremlin, like using "g.V().id().order().by(asc)" to get vertexes ordered by vertex ID. We bring up the issue for we are wondering whether query without specified property, like "g.V()/E().order().by(asc/desc)", is grammatically correct or not, as we find it could be accepted in JanusGraph while get exception above in Neo4j-Gremlin.

 



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