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https://issues.apache.org/jira/browse/TINKERPOP-2681?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17485734#comment-17485734
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ASF GitHub Bot commented on TINKERPOP-2681:
-------------------------------------------
spmallette commented on a change in pull request #1555:
URL: https://github.com/apache/tinkerpop/pull/1555#discussion_r797529098
##########
File path: docs/src/upgrade/release-3.6.x.asciidoc
##########
@@ -29,6 +29,71 @@ Please see the
link:https://github.com/apache/tinkerpop/blob/3.6.0/CHANGELOG.asc
=== Upgrading for Users
+==== mergeV() and mergeE()
+
+One of the most commonly used patterns in Gremlin is the use of
`fold().coalesce(unfold(), ...)` to perform upsert-like
+functionality. While this pattern is quite flexible, it can also be confusing
to new users and for certain use cases
+challenging to get the pattern correctly implemented. For providers, the
pattern is difficult to properly optimize
+because it can branch into complexity quite quickly making it hard to identify
a section of Gremlin for an upsert and
+therefore is not executed as efficiently as it might have been otherwise.
+
+The new `mergeV()` and `mergeE()` steps greatly simplify this pattern and as
the pattern is condensed into a single
+step it should be straightforward for providers to optimize as part of their
implementations. The following example
+demonstrates just how much easier implementing a basic upsert of a vertex has
gotten:
+
+[source,text]
+----
+// prior to 3.6.0, use fold().coalesce(unfold(), ...)
+gremlin> g.V().has('person','name','vadas').has('age', 27).
+......1> fold().
+......2> coalesce(unfold().property('age',30),
+......3>
addV('person').property('name','vadas').property('age',27)).
Review comment:
> I find the example here already quite advanced and not obvious to
understand.
well, i think that's somewhat indicative of why these steps needed to be
added. i tried to pick an easy one already....you should see a "hard" one. 😄
that said, i've added a more simple example along the lines you described.
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> Create merge() step to codify best practice for upsert pattern
> --------------------------------------------------------------
>
> Key: TINKERPOP-2681
> URL: https://issues.apache.org/jira/browse/TINKERPOP-2681
> Project: TinkerPop
> Issue Type: Improvement
> Components: language, process
> Affects Versions: 3.5.1
> Reporter: Dave Bechberger
> Assignee: Stephen Mallette
> Priority: Major
>
> Create a step that codifies the best practice for the upsert functionality
> into a single step to make it easier to use, more discoverable, and easier
> for implementers to optimize.
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