$elemMatch projection

[J Y]

Hi all,

Is this available in API?  I am trying to do an $elemMatch projection, and was not able to get it to work.

This is the mongodb query I am trying to perform:

db.test.find({}, {"change": {"$elemMatch": {"latest": 1}}});

I tried this in cfmongodb:

<cfset result = test.find(criteria={}, keys='{"change" : {"$elemMatch" : {"latest" : 1}}}').asArray() />

Where "latest" is a field in the "change" array.  The result returned does not actually contain the field I am looking for.

Thanks in advance for any help.

[Marc Esher]

Hey JY,

I thought elemMatch was to be used in the criteria document, i.e.

test.find(criteria={"change": {"$elemMatch": {"latest": 1}}})

The keys argument simply limits the fields which are returned.

Marc

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[J Y]

Hi Marc,

We are trying to limit the amount of data that gets returned from a document with a large array using a elemMatch.  The Java driver's find can accept a DBObject that has a elemMatch in it in the keys argument, just looking for a way to pass a struct of that into cfmongodb.

Thanks,

J

[Marc Esher]

So are you saying that using elemMatch in the mongo console works as a key, but doesn't work in your app code?

When you turn on profiling, what do you see as the actual query that Mongo is getting? That's often helpful in debugging.