Return updated document with Monger

Question

In Monger there is a insert-and-return function for returning a newly inserted document.

There is no update-and-return function.

How can I return an updated document from the function that executes the update?

I think I could use save-and-return but it seems to me that I am not able to use operators like $push with this function.

JohnnyHK · Answer 1 · 2013-01-16T02:10:34.057

4

This is the purpose of Monger's find-and-modify function.

;; Atomically find the doc with a language of "Python", set it to "Clojure", and
;; return the updated doc.
(mgcol/find-and-modify collection 
  {:language "Python"} 
  {:$set {:language "Clojure"} }
  :return-new true)

edited Jan 16 '13 at 02:10

answered Jan 16 '13 at 00:12

JohnnyHK

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Thanks. I accepted Leonid's answer because he has the lower reputation and he will benefit more of the bounty. As I cannot accept both answers I at least upvoted yours. Hope that's ok for you. – tobiasbayer Jan 17 '13 at 15:29
@CodeBrickie I can't say I agree since Leonid basically copied my answer, but as Obiwan said: "You must do what you feel is right, of course." – JohnnyHK Jan 17 '13 at 16:15
He copied yours and added a second option. So he produced substantial value as well. – tobiasbayer Jan 18 '13 at 07:19

score 2 · Accepted Answer · edited May 23 '17 at 11:46

I can see two options for you.

First option is to use JohnnyHK's solution with find-and-modify function:

(mc/find-and-modify "users"
  (select-keys my-doc [:_id])
  { $push { :awards { :award "IBM Fellow"
                      :year  1963
                      :by    "IBM" }}}
  :return-new true)

Second option is to use save instead of update. It's a good choice if you already have the entire document loaded from mongodb. You can easily replace mongodb operators like $push with clojure functions like update-in. Manipulation with clojure maps seems for me as better approach. If you have problems with finding clojure alternatives for mongodb operators I can help you.

For my previous example it will look like this:

(mc/save-and-return "users"
  (update-in my-doc [:awards] conj
    { :award "IBM Fellow"
      :year  1963
      :by    "IBM" }))

Myself, I prefer this way, because it looks more Clojure-ish.

Return updated document with Monger

2 Answers2