MongoDb: Aggregation using Groovy language - mongodb

Question

Iam using groovy scripting under SpagoBI. I want to use aggregation.
I want for example to execute the following aggregation:
db.myCollection.aggregate(
[
{
$group : {
_id : { day: { $dayOfMonth: "$recvTime" } }
}
}
]
)
I tried:
DBObject projectFields = new BasicDBObject('$dayOfMonth',"recvTime");
DBObject project=new BasicDBObject('$project',projectFields)
DBObject groupFields = new BasicDBObject( "_id",project);
DBObject group = new BasicDBObject('$group', groupFields);
iterable = db.getCollection('myCollection').aggregate(group)
I got this error:
An unexpected error occured while executing dataset: { "serverUsed" : "192.168.1.160:27017" , "errmsg" : "exception: invalid operator '$project'" , "code" : 15999 , "ok" : 0.0}
Any ideas?
Updates:
the query executed in Mongo shell
db['cygnus_/kurapath_enocean_power_enocean'].aggregate(
... [
... {
... $group : {
... _id : { day: { $dayOfMonth: "$recvTime" } }
... }
... }
... ]
... );
{ "_id" : { "day" : 9 } }
{ "_id" : { "day" : 8 } }
{ "_id" : { "day" : 7 } }
{ "_id" : { "day" : 4 } }
{ "_id" : { "day" : 3 } }
the data stored in mongo db:
db['cygnus_/kurapath_enocean_power_enocean'].find()
{ "_id" : ObjectId("55e81e9631d7791085668331"), "recvTime" : ISODate("2015-09-03T10:19:02Z"), "attrName" : "power", "attrType" : "string", "attrValue" : "2085.0" }
{ "_id" : ObjectId("55e81e9631d7791085668332"), "recvTime" : ISODate("2015-09-03T10:19:02Z"), "attrName" : "power", "attrType" : "string", "attrValue" : "2085.0" }
{ "_id" : ObjectId("55e81e9831d7791085668333"), "recvTime" : ISODate("2015-09-03T10:19:04Z"), "attrName" : "power", "attrType" : "string", "attrValue" : "2077.0" }

Answer 1

From the error, the aggregation is not expecting the $project operator so you should change the projectFields and project variables to show the actual pipeline expressions i.e.
DBObject dateFields = new BasicDBObject("$dayOfMonth", "$recvTime");
DBObject dateObject = new BasicDBObject("day", dateFields);
DBObject groupFields = new BasicDBObject( "_id", dateObject);
DBObject group = new BasicDBObject('$group', groupFields);
iterable = db.getCollection('myCollection').aggregate(group);

Answer 2

In SpagoBI you have 2 ways to create a dataset of type MongoDB:
1) use a dataset of type Query and use JS language
2) use a dataset of type java class and write your code in java
For solution 1 you should create a dataset of type query, select a datasource MongoDB and write on the field QUERY the query in js following the specification written here (http://wiki.spagobi.org/xwiki/bin/view/spagobi_server/data_set#HQueryDataSet28Mongo29)
The button “Edit script” is used to modify the query string and you can find some tip in the wiki. So if the query is SQL you can use a js o groovy script to change the query string (for example apply some logic to create parameters or table names)
You can express your query in this way:
Var query = db.myCollection.aggregate(
[
{
$group : {
_id : { day: { $dayOfMonth: "$recvTime" } }
}
}
]
)