Java with mongodb - mongodb

Question

I am getting following exception when I tried to fetch the data from a mongodb collection. This collection is having very huge data.
The exception is:
com.mongodb.MongoQueryException: Query failed with error code 10334 and error message 'BSONObj size: 24020168 (0x16E84C8) is invalid. Size must be between 0 and 16793600(16MB)' on server 10.15.0.227:27017
And following is my query which I used to get the data from mongodb:
db.getCollection('triggered_policies').aggregate(
[{ "$match" : { "policy_name" : "EIQSOC-1040-ec"}},
{ "$project" : { "cust_created_at" : { "$add" : [ "$created_at" , 19800000]} , "event_ids" : "$event_ids" , "trigger_time" : "$trigger_time" , "created_at" : "$created_at" , "triggered_rules" : "$triggered_rules"}},
{ "$sort" : { "created_at" : -1}},
{ "$group" :
{ "_id" :
{
"$hour" : "$cust_created_at"} ,
"triggered_policies" : { "$addToSet" : { "trigger_time" : "$trigger_time" , "created_at" : "$created_at" , "event_ids" : "$event_ids" , "triggered_rules" : "$triggered_rules"}
}
}
},
{ "$sort" : { "_id" : 1}}
])
Following is the exact exception which we are getting:
Error: getMore command failed: {
"ok" : 0,
"errmsg" : "BSONObj size: 25994482 (0x18CA4F2) is invalid. Size must be between 0 and 16793600(16MB)",
"code" : 10334
}
Please help us to solve the issue.

Answer 1

Looks like the document created during aggregation exceeds the 16MB size restriction in mongo db. You might have to change your aggregate query to not accumulate too much data into a single document which exceeds the 16MB size limit.
Below is the quote from Mongo DB documentation:
BSON Document Size
The maximum BSON document size is 16 megabytes.
The maximum document size helps ensure that a single document cannot use excessive amount of RAM or, during transmission, excessive amount of bandwidth. To store documents larger than the maximum size, MongoDB provides the GridFS API. See mongofiles and the documentation for your driver for more information about GridFS.