MongoDb array updating

Question

I am trying to update the following document in Mongodb.

    doc = { id : 10 , graph :[{userId:1,children:[2]},{userId:2,children:[]}]}

    db.test.insert(doc)

then I perform two updates:

db.test.update( {'id':10,'graph.userId' : 1}, { $push:{'graph.$.children':10}})

db.test.update( {'id':10,'graph.userId' : 1},{ $push:{'graph':{'userId':10,'children':[]}}})

(Saddly :

db.test.update( {'id':10,'graph.userId' : 1},{ $push:{'graph.$.children':10},$push:{'graph':{'userId':10,'children':[]}}})

does not work)

Is there a way to update these simultaneously ?

Thanks a lot

Andrew Orsich · Accepted Answer · 2011-10-31 19:35:57Z

2

You can bundle multiple update operations together, but the only issue with what you've written in pseudo code is that the elements you're pushing belong to different arrays (graph and graph.children respectively.) This needs to be done in two pushes.

Try this:

db.test.update( { id:10, 'graph.userId':1 }, 
        { $push:{'graph.$.children' : 4 }, $push:{'graph' : {'userId':4,'children':[]}} } )

edited Oct 31, 2011 at 19:35

Andrew Orsich

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answered Oct 31, 2011 at 18:59

jpredham

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2 Comments

jlezard Over a year ago

really sorry but it turns out this does not work. I have edited the question, thanks

light24bulbs Over a year ago

wont the second push override the first since they have the same key

Rod · Accepted Answer · 2013-02-12 17:10:38Z

1

The multiple keys in the modifier array stop it from working. You have to do two updates to do this if I read your shema right cos you are trying to push a new child onto the current position and push a new record into the subdocument of the parent.

The thing that stops it is the children[] setting. Mongo just does not know where to set that.

I suppose you could try:

db.test.update( {'id':10,'graph.userId' : 1},{ $push:{'graph.$.children':10},$pushAll:{'graph':{{'userId':10,'children':[]}}}})

But it is a long shot

edited Feb 12, 2013 at 17:10

Rod

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answered Nov 2, 2011 at 13:51

Sammaye

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1 Comment

jlezard Over a year ago

thanks for your help, a pitty the simultneous update does not work

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