[jira] [Commented] (TINKERPOP-3184) Please allow the path() step to take an optional from and to label

["Taylor Riggan (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TINKERPOP-3184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18016811#comment-18016811 ] 

Taylor Riggan commented on TINKERPOP-3184:
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How is this different from the current support of using from() or to() as a modulator for path()?

Example graph:

{{g.addV('Person').property('name','John').as('a').}}
{{    addV('Place').property('city','New York').as('b').}}
{{    addV('Thing').property('type','car').as('c').}}
{{    addE('visited').from('a').to('b').}}
{{    addE('has').from('b').to('c')}}

 

Query:

{{g.V().hasLabel('Person','name','John').}}
{{    outE('visited').inV().as('start').}}
{{    outE('has').inV().}}
{{    path().from('start').by(label)}}

 

Result:

{{path[Place, has, Thing]}}

 

> Please allow the path() step to take an optional from and to label
> ------------------------------------------------------------------
>
>                 Key: TINKERPOP-3184
>                 URL: https://issues.apache.org/jira/browse/TINKERPOP-3184
>             Project: TinkerPop
>          Issue Type: Wish
>    Affects Versions: 3.7.4
>            Reporter: Martin Häusler
>            Priority: Major
>
> Hello,
> I am once again dealing with paths. I noticed that it is currently possible to do the following:
> {code:java}
> traversal().V()
>    // ... navigation...
>    .path()
>    .unfold()
> {code}
> ... which is very neat. I was wondering if I can also get the path between a label and the current vertex. Turns out, I can:
> {code:java}
> traversal().V()
>    // ... navigation ...
>    .as("from")
>    // ... navigation...
>    .flatMap ( t-> t.path().subPath("from", null).iterator())
> {code}
> That is very useful! But it's a shame that the functionality is locked behind a lambda expression, which is not available in all scenarios. Moreover, gremlin optimizes away the path information tracking if no "path()" step is used in the query, so the lambda solution always requires some additional artificial steps on top.
> My proposal would be to add the following overload to the "path()" method:
> {code:java}
> public default GraphTraversal<S, Path> path(String fromLabel, String toLabel)
> {code}
> ... which behaves exactly like the lambda above. Both "fromLabel" and "toLabel" should accept NULL (same as "subPath(...)") which means start/end of the path respectively. Therefore calling "path()" would be the same as "path(null, null)".



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