Is there a better way to export a mongodb query to a new collection?

What I want: I have a master collection of products, I then want to filter them and put them in a separate collec开发者_JS百科tion.

db.masterproducts.find({category:"scuba gear"}).copyTo(db.newcollection)

Of course, I realise the 'copyTo' does not exist.

I thought I could do it with MapReduce as results are created in a new collection using the new 'out' parameter in v1.8; however this new collection is not a subset of my original collection. Or can it be if I use MapReduce correctly?

To get around it I am currently doing this: Step 1: /usr/local/mongodb/bin/mongodump --db database --collection masterproducts -q '{category:"scuba gear"}'

Step 2: /usr/local/mongodb/bin/mongorestore -d database -c newcollection --drop packages.bson

My 2 step method just seems rather inefficient!

Any help greatly appreciated.

Thanks

Bob

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You can iterate through your query result and save each item like this:

db.oldCollection.find(query).forEach(function(x){db.newCollection.save(x);})

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1. You can create small server side javascript (like this one, just add filtering you want) and execute it using eval
2. You can use dump/restore in the way you described above
3. Copy collection command shoud be in mongodb soon (will be done in votes order)! See jira feature.

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You should be able to create a subset with mapreduce (using 'out'). The problem is mapreduce has a special output format so your documents are going to be transformed (there is a JIRA ticket to add support for another format, but I can not find it at the moment). It is also going to be very inefficent :/

Copying a cursor to a collection makes a lot of sense, I suggest creating a ticket for this.

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there is also toArray() method which can be used:

//create new collection 
db.creatCollection("resultCollection")

// now query for type="foo" and insert the results into new collection
db.resultCollection.insert( (db.orginialCollection.find({type:'foo'}).toArray())