Getting the result of an update operation

[manast]

Hello,

According to the documentation in mongodb (http://www.mongodb.org/display/DOCS/Updating#Updating-CheckingtheOutcomeofanUpdateRequest), it is possible to get the result of an update operation. In some cases it is extremely useful to be able to know if the update did update something or not. For instance in my application I want to update all the clients that are observing some document if that document has been changed or not. I can fake this by first getting the document and only updating if necessary, but it is quite inconvenient for several reasons.

Is there any efficient way to get the update result information in mongoose or any good workaround for it?

regards.

[aheckmann]

right now the number of affected documents is passed to the callback.

Thing.update(query, update, function (err, affected) {
  // affected is the number of docs that were updated
})

1. i just fixed a bug with this when using strict schemas but it has not been released yet. if you are not using strict schemas the number returned will be correct

2. the driver now also passes the actual return document but it's not in the latest release of mongoose yet. we'll get that in the next release as well.

[manast]

Thanks for the quick response :).

Ok, I was actually testing with a strict schema and the number returned was 1, which as I understood was the number of elements that matched the query, not the number of elements that actually changed due this update operation.

So If I understood it correctly, that number will be zero if I try to update one document with the same values that it already has, right?

On Apr 26, 2012, at 8:09 PM, Aaron Heckmann wrote:

right now the number of affected documents is passed to the callback.

Thing.update(query, update, function (err, affected) {
 // affected is the number of docs that were updated
})

1. i just fixed a bug with this when using strict schemas but it has not been released yet. if you are not using strict schemas the number returned will be correct

2. the driver now also passes the actual return document but it's not in the latest release of mongoose yet. we'll get that in the next release as well.

---

Reply to this email directly or view it on GitHub:
#867 (comment)

[aheckmann]

affected is the number of docs updated, even if the new values are identical. this comes straight from mongo.

[manast]

I see. That was what I suspected. It is not really the same thing as I was asking then, as you see from the link I sent above, it should be possible to know from mongo if a document actually was changed by the update or not. Of course if we can get back the updated document after updating, as you mentioned, then we could also check it by hand. It will solve the issue although slightly less optimal than having mongo telling us automatically.

regards.

On Apr 26, 2012, at 9:36 PM, Aaron Heckmann wrote:

affected is the number of docs updated, even if the new values are identical. this comes straight from mongo.

---

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#867 (comment)

[aheckmann]

in master we have support for the findAndModify command which lets us do an atomic update and return the doc in one op. this will be available in the 3.x release.

[manast]

ok. That will be quite useful, although not so optimal as just getting what really was updated. Specially important in the case of using the $addToSet command: { $addToSet : { a : { $each : [ 3 , 5 , 6 ] } } }

In this case it will be really useful to know what elements actually were added to the set, to notify listeners with that information. Even if it can be done using findAndModify it is slower and also non-atomic.

[aheckmann]

this isn't currently possible with mongo.

[timoxley]

Related: go watch, vote and/or comment on this issue in hopes that the mongodb team does something about it soon. This has been a major headache for me. https://jira.mongodb.org/browse/SERVER-3409

trying out this fix:

"For the moment, you can add an extra filter to your query condition so
that, if nothing is updated, 'updatedExisting' will be false."

db.foo.update({_id: 'some_id', array: {$ne: 'foo'}}, { $addToSet: { array: 'foo' }})

From: https://groups.google.com/d/topic/mongodb-user/DPW90mH4-0k/discussion

I wonder if there's a way I can get this functionality while still using a mongoose object's array methods? i.e. still being able to use addToSet + model.save(), currently this necessarily requires me to save the object at the time of adding the items to the set.

[aheckmann]

today we'd need to use foo.update() directly

[madsviktor]

Is there any update on this? I'm using v. 3.5.3 and it seems like the update callback is still returning the number of affected documents (and not the actual return doc.)

Regards.

[efosao]

@madsviktor It looks like findOneAndUpdate may do what you're looking for...

http://mongoosejs.com/docs/api.html#model_Model.findOneAndUpdate

[madsviktor]

@efosao Oh, you're so right - findAndModify have been implemented there instead - thanks for the help man :)

[aheckmann]

The return doc is passed as the third argument:
http://mongoosejs.com/docs/api.html#model_Model.update

On Wednesday, March 20, 2013, madsviktor wrote:

Is there any update on this? I'm using v. 3.5.3 and it seems like the
update callback is still returning the number of affected documents (and
not the actual return doc.)

Regards.

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/867#issuecomment-15185900
.

Aaron
@aaronheckmann https://twitter.com/#!/aaronheckmann

[aheckmann]

I meant the details of the operation. For the document itself, yes, use the
findAndModify variants.

On Wednesday, March 20, 2013, Aaron Heckmann wrote:

The return doc is passed as the third argument:
http://mongoosejs.com/docs/api.html#model_Model.update

On Wednesday, March 20, 2013, madsviktor wrote:

Is there any update on this? I'm using v. 3.5.3 and it seems like the
update callback is still returning the number of affected documents (and
not the actual return doc.)

Regards.

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/867#issuecomment-15185900
.

Aaron
@aaronheckmann https://twitter.com/#!/aaronheckmann

Aaron
@aaronheckmann https://twitter.com/#!/aaronheckmann

[JorgeCeja]

For future reference:

var query   = { id: 8 }; 
var update  = { title: "new title" }; 
var options = { new: true }; 
MyModel.findOneAndUpdate(query, update, options, function(err, doc){ 
  // Done! 
  // doc.title = "new title" 
});

Credit: https://davidburgos.blog/return-updated-document-mongoose/