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https://issues.apache.org/jira/browse/TINKERPOP-2481?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17257079#comment-17257079
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Stephen Mallette commented on TINKERPOP-2481:
---------------------------------------------
After some research, I came across some old discussion on this strategy here:
TINKERPOP-1412 - I think Marko's final comment on that make sense to me. This
strategy was never about performance of chained {{identity()}} steps but more
about removing an {{identity()}} which might have normalized the Gremlin enough
for another strategy to do its work properly. On the other hand this issue is
also as much an issue with {{PathRetractionStrategy}}:
{code}
gremlin>
g.withoutStrategies(PathRetractionStrategy).V().match(__.as("a").out("knows").as("b")).identity()
==>[a:v[1],b:v[2]]
==>[a:v[1],b:v[4]]
{code}
We really shouldn't have situations where "correctness" or "consistency" of
results is upset by a strategy and shouldn't use one strategy (in this case
{{IdentityRemovalStrategy}}) to ensure a particular result based on another. So
ultimately, I think the fix here is to {{PathRetractionStrategy}} and to
install {{IdentityRemovalStrategy}}. Created TINKERPOP-2499 for the former.
> IdentityRemovalStrategy not installed
> -------------------------------------
>
> Key: TINKERPOP-2481
> URL: https://issues.apache.org/jira/browse/TINKERPOP-2481
> Project: TinkerPop
> Issue Type: Improvement
> Components: process
> Affects Versions: 3.4.8
> Reporter: Stephen Mallette
> Priority: Minor
>
> I'm not sure why but {{IdentityRemovalStrategy}} is not in play and almost
> looks like it never has been, yet I fairly certain we've gone about life
> thinking it was one of our standard strategies. Perhaps this issue title will
> shift once this is given more thought but I came to [notice this
> issue|https://groups.google.com/g/gremlin-users/c/HVtldzV0Xk8/m/saCBYsEQBgAJ]
> with this example:
> {code}
> gremlin> g.V().match(__.as("a").out("knows").as("b")).identity()
> ==>[]
> ==>[]
> gremlin>
> g.withStrategies(IdentityRemovalStrategy.instance()).V().match(__.as("a").out("knows").as("b")).identity()
> ==>[a:v[1],b:v[2]]
> ==>[a:v[1],b:v[4]]
> {code}
> So if the strategy had been in play, {{PathRetractionStrategy}} wouldn't have
> trimmed the history. Or, perhaps {{PathRetractionStrategy}} should have been
> smarter....
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