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https://issues.apache.org/jira/browse/TINKERPOP-2961?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17752088#comment-17752088
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Miracy Cavendish commented on TINKERPOP-2961:
---------------------------------------------
Many thanks for your help!(y) I have a better understanding of Gremlin's
"match" step now.
It would be appreciated if you could throw exceptions for such queries, since
developers may carelessly write unsolvable queries without warning.
For the additional questions, any further investigation on it would also be
highly appreciated!
> Missing exceptions for unsolvable match pattern, which may lead to logic
> inconsistency
> --------------------------------------------------------------------------------------
>
> Key: TINKERPOP-2961
> URL: https://issues.apache.org/jira/browse/TINKERPOP-2961
> Project: TinkerPop
> Issue Type: Bug
> Components: process
> Affects Versions: 3.6.0
> Reporter: Miracy Cavendish
> Priority: Major
> Attachments: create-8.log
>
>
> Hi all! From
> [Discord|https://discord.com/channels/838910279550238720/1064868348925583442/threads/1117146194666332250].
> We noticed that in some cases unsolvable matching will not lead to the
> exception "unsolvable pattern" in Gremlin.
> For a simple example, in the empty graph, the following query will not lead
> to an exception, while it will result in an exception in the GraphModern:
> {code:java}
> g.V().match(__.as("A").out().as("B"), __.as("C").out().as("B"),
> __.as("D").out().as("A"))
> {code}
> In more complex cases, this missing may lead to a worse result.
> For example, in the graph created by attachment _create-8.log_
> {code:java}
> g.V().match(
> __.as("n2").out().as("n1"),
> __.as("n2").in().in().in().both().in().as("n1"),
> __.as("n2").both().in().in().as("n3"),
> __.as("n3").in().both().as("n2"),
> __.as("n2").in().in().in().in().both().as("n4"),
> __.as("n2").out().both().in().as("n4"),
> __.as("n3").both().as("n4"),
> __.as("n1").in().both().both().both().as("n5")
> ).dedup().count()
> =>306691
> g.V().match(
> __.as("n2").out().as("n1"),
> __.as("n2").in().in().in().both().in().as("n1"),
> __.as("n2").both().in().in().as("n3"),
> __.as("n3").in().both().as("n2"),
> __.as("n4").both().out().out().out().out().as("n2"),
> __.as("n2").out().both().in().as("n4"),
> __.as("n3").both().as("n4"),
> __.as("n1").in().both().both().both().as("n5")
> ).dedup().count()
> =>306075
> {code}
> The two queries are equivalent, the only difference is the expression of the
> traversal "__.as("n4").both().out().out().out().out().as("n2")".
> I am not sure which of their results in the correct result, but the logic
> inconsistency indicates that the missing exception may cause worse results
> than we thought before.
> After the discussion with [~spmallette], we believe that it would be better
> if detect the unsolvable pattern before the execution.
> {*}In addition{*}, *it would be highly appreciated if someone can reproduce
> and confirm the logic inconsistency in the complex cases. I think it may
> imply other potential issues of the traversal strategies.* And if such logic
> inconsistency still exists using both solvable equivalent patterns, we will
> reduce & report is ASAP.
>
> Best regards,
> Joye Mang
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