Update Mongo variable value with variable itself

Question

I am not at all familiar with javascript and was hoping I could receive some help with a mongo update of a variable.

I have looked at the following question : Pass variables into mongo updates?

but was confused a bit with the looping and the syntax.

I have a field called "name": "MyName" I am looking for a way to get the following results using a mongo shell command: "name": "MyName Is" with a query as well

How would I do that? Is this a completely incorrect approach?

db.collection.update({"old_id":{$regex:".*_change.*"}}, {$set:{"name":"name" + " Is"}}, {multi:true})

Thanks!

Looks to be correct, have you tried it? Does it produce the desired results? — Rishi
– Rishi, Commented Feb 12, 2014 at 20:59

Community · Accepted Answer · 2017-05-23 12:31:31Z

2

The simple answer is: You cannot! You cannot update a field using another field. So you cannot update a field using itself. See also here.

BTW:

This

 $set:{"name":"name" + " Is"}

will set the name property to "name Is".

edited May 23, 2017 at 12:31

CommunityBot

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answered Feb 12, 2014 at 21:03

heinob

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3 Comments

RCN Over a year ago

thank you so much! I had not seen that question/answer. Guess, I can write a python script to loop through. Thanks

RCN Over a year ago

I sort of figured it would only recognize that as a string, but I was uncertain how to reference the variable name

heinob Over a year ago

You can reference field names in the aggregation_framework (docs.mongodb.org/manual/aggregation) using $.

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