tuple/array in aggregation with $addToSet

[Christian Schulz]

Hi,

is there a simple way to overcome this problem?

Thanks in advance

Christian

col.aggregate([

    { '$group' : 

    {'_id' : {'anyid':"$anyid"},

    'loc' : {'$addToSet' : ('$lat','$lon') }}}])    

failed: exception: aggregating group operators are unary ($addToSet)

[Gary R]

I believe that $addToSet, in aggregation framework, tries to push one object to an array.  It's complaining because ('$lat','$lon') appears to be two objects not a single tuple (if that's what you'd intended).  If you're trying to $addToSet one value after another, $addToSet now has an operator "each" which accepts an array of values.

{ $addToSet: { <array name> : { $each: [ value1, value2, etc ]  } } }

Gary R.

[Asya Kamsky]

There is no $each operator in aggregation framework.

However all OP needs to do is change the document from {"$lat","$lon"} to { lon:"$lon", lat:"$lat"}  as the former is not legal JSON and the latter is.

Notice I also reverse the order of longitude and latitude as lon, lat is the expected order of coordinates in MongoDB.

Asya

[Gary R]

Thanks for the correction, Asya.

So in aggregation, without "each," there is no way to push/addToSet just the values for TWO fields except within a document as you described?

If you have
{ _id:1, name:1, a:2, b:3 }
( _id:2, name:1, a:4, b:5 }

Is there no way to $group by $name and push BOTH $a and $b values into an array?

{ name:1, anArray[2,3,4,5] }

Gary R.

[Asya Kamsky]

That's correct -there is no way to do this in aggregation framework right now.

[Denis Pshenov]

That's unfortunate. Also needed this feature.