Simulate a MERGE in Neptune's OpenCypher implementation

Question

I'm trying to run a MERGE query against an AWS Neptune database using their new OpenCypher implementation but MERGE is not yet supported as a clause.

Is there a way to get the behaviour of a MERGE without using a MERGE in Neptune's OpenCypher implementation?

I'm hoping it's possible to do something like:

MATCH (ee:Person {name: "Sam"})

IF ee IS NULL THEN
  CREATE ...
ELSE
  SET ee += {...}
END

Obviously this is just pseudocode, but is there any way of achieving this behaviour without handling it in the application making the call?

bechbd · Accepted Answer · 2021-11-24T17:51:14.907

openCypher does not provide a robust capability to perform the type of logic in a query that you show in your pseudocode. Until MERGE is a supported clause in AWS Neptune the best way to achieve this functionality is to use the Gremlin pattern for this as described here. Neptune provides the ability to use both openCypher and Gremlin (via drivers or over HTTPS) on property graph data stored in Neptune. For your pseudo code above the Gremlin equivalent would look like this:

g.V().
  has('Person', 'name', 'Sam').
  fold().
  coalesce(
    addV('NEW LABEL').property('propertyName', 'foo'),
    property('updateProperty', 'bar'))

UPDATE - As of the 1.1.0.0 version of Amazon Neptune the MERGE clause is now supported.

Simulate a MERGE in Neptune's OpenCypher implementation

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