[
https://issues.apache.org/jira/browse/TINKERPOP-968?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15211996#comment-15211996
]
pieter martin commented on TINKERPOP-968:
-----------------------------------------
After a discussion in hipchat it was decided that the semantics will stay as is
via the {{choose}} step. i.e. The user must manually union the result if that
is the desired outcome.
{code}
final TinkerGraph g = TinkerGraph.open();
Vertex a1 = g.addVertex(T.label, "A", "name", "a1");
Vertex b1 = g.addVertex(T.label, "B", "name", "b1");
a1.addEdge("ab", b1);
GraphTraversal gt1 = g.traversal().V(a1).optional(__.out("ab", "bb")).path();
while (gt1.hasNext()) {
System.out.println(gt1.next());
}
{code}
will return
{code}
[v[0], v[2]]
{code}
and not
{code}
[v[0], v[2]]
[v[0]]
{code}
> 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.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
