[jira] [Commented] (TINKERPOP-2302) Add isOnGraphComputer() field accessor to ElementMapStep

["Stephen Mallette (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TINKERPOP-2302?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16938978#comment-16938978 ] 

Stephen Mallette commented on TINKERPOP-2302:
---------------------------------------------

I'm good with the "narrow" direction. Once that merges, we can consider the more advanced suggestions - {{GraphComputing}} should probably have that method ultimately. 

> Add isOnGraphComputer() field accessor to ElementMapStep
> --------------------------------------------------------
>
>                 Key: TINKERPOP-2302
>                 URL: https://issues.apache.org/jira/browse/TINKERPOP-2302
>             Project: TinkerPop
>          Issue Type: Improvement
>          Components: process
>    Affects Versions: 3.5.0, 3.4.4
>            Reporter: Dan LaRocque
>            Priority: Minor
>
> TINKERPOP-2284 added {{ElementMapStep}}.
> This step implements {{GraphComputing}}, so it defines that interface's {{onGraphComputer()}} method.  The method sets a private boolean field.
> For any implementation that wants to alter {{ElementMapStep}} behavior by replacing instances of the step with an alternative implementation (maybe a subclass), it could be convenient to make private the {{onGraphComputer}} state accessible.  I think the rest of {{ElementMapStep}}'s public state is already accessible; it's just this field that is private.
> There are a few ways to go about this.
> * We could add an {{isOnGraphComputer()}} method to just {{ElementMapStep}}, or make {{onGraphComputer}} protected.  This is the narrowest version of the change.
> * We could add an {{isOnGraphComputer()}} method to the {{GraphComputing}} interface.  This would affect a bunch of implementing steps.  Most implementations on tp34 have an internal boolean field storing this state, so it would be easy on those.  However, [{{GraphStep}} does not have a boolean onGraphComputer field|https://github.com/apache/tinkerpop/blob/tp34/gremlin-core/src/main/java/org/apache/tinkerpop/gremlin/process/traversal/step/map/GraphStep.java#L131-L135]:
> {code}
>     @Override
>     public void onGraphComputer() {
>         this.iteratorSupplier = Collections::emptyIterator;
>         convertElementsToIds();
>     }
> {code}
> We could maybe implement this without adding another field, but it would be simpler to do that.
> *Altering this interface would also break any third-party implementations of {{GraphComputing}}.*
> * We could add create a {{GraphComputing}} subinterface that adds an {{isOnGraphComputer()}}, and only implement it where it's already made simple to do by the existence of a boolean field.  This somewhere in between the first two approaches in terms of scope.
> I'm going to open a PR taking the first, narrowest possible approach, where I'm only touching {{ElementMapStep}}.  I'd be happy to rework it to one of the alternatives, if desired.



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