[
https://issues.apache.org/jira/browse/TINKERPOP-1506?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15597581#comment-15597581
]
Daniel Kuppitz commented on TINKERPOP-1506:
-------------------------------------------
These comments still hold true. {{optional}} and {{coalesce}} are not
interchangeable.
{noformat}
gremlin> g.V().coalesce(out("knows"), identity()).coalesce(out("created"),
identity()).path()
==>[v[1],v[2],v[2]]
==>[v[1],v[4],v[5]]
==>[v[1],v[4],v[3]]
==>[v[2],v[2],v[2]]
==>[v[3],v[3],v[3]]
==>[v[4],v[4],v[5]]
==>[v[4],v[4],v[3]]
==>[v[5],v[5],v[5]]
==>[v[6],v[6],v[3]]
gremlin> g.V().optional(out("knows")).optional(out("created")).path()
==>[v[1],v[2]]
==>[v[1],v[4],v[5]]
==>[v[1],v[4],v[3]]
==>[v[2]]
==>[v[3]]
==>[v[4],v[5]]
==>[v[4],v[3]]
==>[v[5]]
==>[v[6],v[3]]
{noformat}
> Optional/Coalesce should not allow sideEffect traversals.
> ---------------------------------------------------------
>
> Key: TINKERPOP-1506
> URL: https://issues.apache.org/jira/browse/TINKERPOP-1506
> Project: TinkerPop
> Issue Type: Improvement
> Components: process
> Affects Versions: 3.1.4, 3.2.2
> Reporter: Marko A. Rodriguez
>
> It took me a long time to realize what was wrong with a traversal I wrote
> that used {{optional(blah.sideEffect.blah)}}. {{optional()}} maps to
> {{ChooseStep}} under the hood and the provide traversal is first tested for a
> {{hasNext()}}. If so, the it plays itself out. The problem is that if there
> is a side-effect in the traversal child, then it gets executed twice.
> {code}
> gremlin> g = TinkerGraph.open().traversal()
> ==>graphtraversalsource[tinkergraph[vertices:0 edges:0], standard]
> gremlin> g.inject(1).optional(addV('twin'))
> ==>v[1]
> gremlin> g.V().valueMap(true)
> ==>[id:0,label:twin]
> ==>[id:1,label:twin]
> {code}
> We should NOT allow {{optional()}} to have {{SideEffectStep}} steps in it so
> as not to cause unexpected behavior. {{StandardVerificationStrategy}} can
> analyze and throw an exception if necessary.
> Also, {{coalesce()}} has a similar problem, though perhaps it can be a useful
> 'technique.'
> {code}
> gremlin> g = TinkerGraph.open().traversal()
> ==>graphtraversalsource[tinkergraph[vertices:0 edges:0], standard]
> gremlin> g.inject(1).coalesce(addV('twin1').limit(0), addV('twin2'))
> ==>v[1]
> gremlin> g.V().valueMap(true)
> ==>[id:0,label:twin1]
> ==>[id:1,label:twin2]
> gremlin>
> {code}
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
