How to get NULL as COALESCE VALUE

[Sanjay Sharma]

I am using COALESCE to return the alternate value if a traversal does not exists. below is the query

g.V('machine1').project('machine', 'make').by(identity()).by(coalesce(out('ofMake'), constant('null'))

this works just fine but when i use this query in java gremlin driver, i get back following JAVA TYPES in the RESULT object,

Machine as DetachedVertex type

Make as java.lang.String with value NULL, and if it exists then DetachedVertex type.

This makes me do few if's and else in my code, Is it possible to make query return NULL as an OBJECT instead of String , so that i can simple check NOT NULL condition ? 

[Daniel Kuppitz]

Using nulls in traversals is a bad idea as it mostly won't work. You can rewrite your traversal though:

g.V('machine1').

  choose(outE('ofMake'),

           __.project('machine','make').

                by().

                by(out('ofMake')),

           __.project('machine'))

Then make wouldn't be part of the map, but at least in Java result.get('make') would return null and I guess that's all you need.

Cheers,

Daniel

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