[jira] [Commented] (TINKERPOP-968) Add first class support for an optional traversal

["Marko A. Rodriguez (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TINKERPOP-968?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15125408#comment-15125408 ] 

Marko A. Rodriguez commented on TINKERPOP-968:
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We had {{optional()}} in TinkerPop2. Its actually quite easy to implement. I'm wondering why we don't have it in TinkerPop3 and I believe .... ?? ... that [~dkuppitz] has an argument against it. ? 

Note that if we do implement it for TinkerPop3, we might want to compile it as:

{code}
g.V().hasLabel('a').optional(out('ab')) ==> g.V().hasLabel('a').union(identity(), out('ab'))
{code}

Is that the expected semantics -- sorta like {{emit().repeat()}}? The reason for this is because we would want it to use global traversal in OLAP and well, such {{branch/}} semantics are already implemented for us. Thoughts?


> Add first class support for an optional traversal
> -------------------------------------------------
>
>                 Key: TINKERPOP-968
>                 URL: https://issues.apache.org/jira/browse/TINKERPOP-968
>             Project: TinkerPop
>          Issue Type: Improvement
>          Components: process
>    Affects Versions: 3.1.0-incubating
>            Reporter: pieter martin
>
> Both SparQL and Cypher use the "Optional" keyword to indicate an optional traversal. SQL uses the "left join".
> Gremlin has no first class support for an optional traversal. It can be achieved with the choose step but it is verbose, unintuitive and not what the choose step is intended for.
> The benefits of optional traversals are many. In particular it makes it trivial to load complete subgraphs/trees with one easy to read intuitive gremlin statement.



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