Conditional projection with arrays.

I am basically doing an aggregation to count the number of documents that falls on specific criteria. I am not using Map reduce because I want to do more than one at once.

this is an example of my document

{
   "_id" : ...,
   "Field1" : ....,
   "Field2" : ....,
   "Field3" : ....,
   "FieldDocument1" : {

        "Field5" : ....,
        "Field6" : ....,
        ......

   },
   "FieldDocument2" : {
        "Field7" : ....,
        "FieldArray1" : [....],
        "FieldArray2" : [
               "Field8" : value,
               "FieldArrayToQuery" : [
                                       {"FieldToQuery1" : value,"FieldToQuery1" : value},
                                                                   {"FieldToQuery1" : value,"FieldToQuery1" : value},
                                ],

        ],        ......
   }
}

And this is my query:

db.events.aggregate([

    {$match : {

        "Field1": value

    }},

    {$project: {

        count : { $literal: "count" },

        count1: {

                $cond:[{$eq : [ "$FieldDocument1.Field5" , value]},1,0]

        },

        count2: {

                $cond:[

                        {"FieldDocument2.FieldArray2.FieldArrayToQuery" : { $elemMatch : { FieldToQuery1: value, FieldToQuery1: value}}},

                        1,

                        0

                      ]

        }

        

    }},

    {$group : {

            _id : "$count",

            count1Count : {$sum: "$count1"},
            count2Count : {$sum: "$count2"},

    }},

])

The first count works fine, but when I add the second count I get this error message:

uncaught exception: aggregate failed: {

"errmsg" : "exception: dotted field names are only allowed at the top level",

"code" : 16405,

"ok" : 0

}

is there anyway to have complex conditional projection with arrays?

Not quite like that - can you explain what you want to have as a
result (rather than aggregate syntax you are trying to use).
I'm not sure if I'm understanding what you want to get - and I
hesitate to make a suggestion since it might be for slightly
difference scenario than you have.

Basically, What I am trying to do is multiple counts based on different criteria at once.

I want to do a count based on different fields and an criteria, but all of them have a common criteria, so I was hoping to get them all at once. I managed to get most of them, but I am running on trouble when try to do conditional projection for arrays.

Any advise?

The problem is the syntax you are using is for find or $match, not $project:

 {"FieldDocument2.FieldArray2.FieldArrayToQuery" : { $elemMatch : {
FieldToQuery1: value, FieldToQuery1: value}}} is not a legal way to
compare fields in a conditional ($cond) projection.

You can use {$and:[ {$eq:[ "field1",value1  ] }, { $eq : [ $field2",value2 ] } ]

But you have to unwind arrays before you pass them through group for
aggregation...

Thanks Kamsky!

I was hoping to do it without unwinding, :(. 

I'm doing it now with map reduce, because I cannot accomplish what I want just with Aggregation.