[
https://issues.apache.org/jira/browse/TINKERPOP-2095?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=16690026#comment-16690026
]
ASF GitHub Bot commented on TINKERPOP-2095:
---
dkuppitz opened a new pull request #997: TINKERPOP-2095 GroupStep looks for
irrelevant barrier steps
URL: https://github.com/apache/tinkerpop/pull/997
https://issues.apache.org/jira/browse/TINKERPOP-2095
This PR fixes a bug that somehow managed to stay unnoticed for years.
Prior this PR we got this:
```
gremlin>
g.V().hasLabel('person').as('p').out('created').group().by('name').by(select('p').values('age').sum())
java.lang.Long cannot be cast to
org.apache.tinkerpop.gremlin.process.traversal.traverser.util.TraverserSet
```
Now we get this:
```
gremlin>
g.V().hasLabel('person').as('p').out('created').group().by('name').by(select('p').values('age').sum())
==>[ripple:32,lop:96]
```
The fix was made for both - `GroupStep` and `GroupSideEffectStep`. I also
had to fix `ComputerVerificationStrategy`; it didn't detect that
`select('p').values('age')` is leaving the star-graph.
Without the `ComputerVerificationStrategy` fix:
```
gremlin>
g.V().hasLabel('person').as('p').out('created').group().by('name').by(select('p').values('age').sum())
==>[ripple:0,lop:0]
```
With the `ComputerVerificationStrategy` fix:
```
gremlin>
g.V().hasLabel('person').as('p').out('created').group().by('name').by(select('p').values('age').sum())
Local traversals may not traverse past the local star-graph on
GraphComputer: [SelectOneStep(last,p), PropertiesStep([age],value),
SumGlobalStep]
```
`docker/build.sh -t -i -n` passed.
VOTE +1
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> GroupStep looks for irrelevant barrier steps
>
>
> Key: TINKERPOP-2095
> URL: https://issues.apache.org/jira/browse/TINKERPOP-2095
> Project: TinkerPop
> Issue Type: Bug
> Components: process
>Affects Versions: 3.3.4
>Reporter: Daniel Kuppitz
>Assignee: Daniel Kuppitz
>Priority: Major
>
> {{GroupStep}} looks for a {{Barrier}} step to determine the reducing
> bi-operator. This is wrong and I'm really surprised that this has never been
> spotted before.
> {noformat}
> gremlin>
> g.V().hasLabel('person').as('p').out('created').group().by('name').by(select('p').values('age').sum())
> java.lang.Long cannot be cast to
> org.apache.tinkerpop.gremlin.process.traversal.traverser.util.TraverserSet
> Type ':help' or ':h' for help.
> Display stack trace? [yN]
> {noformat}
> In the query above the first barrier step is a {{NoOpBarrier}} step (added by
> {{PathRetractionStrategy}}). This step obviously has no reducing bi-operator.
> What we really want to do is look for the first barrier step that is not a
> {{LocalBarrier}} step.
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