MongoDb - Embedding or reference? - mongodb

Question

I come from SQL relation world, and have a question that involves mongodb schema design.
The reality that i need to represent contains:
Users, and monthly reports (with multiple daily reports).
I want to figure out if in mongodb, is better to embedded reports objects into the Users collection, or to have 2 separate collection referenced by id.
Embedded solution:
User:{
name:
surname:
monthlyReports: [{
month: "January 2014"
dailyReport: [{
day: 1
singleReport: [
{ report1}, {report2}, ...
]
}, {
day: 2
singleReport: [
{ report1}, {report2}, ...
]
}
]
},
{
/*
february 2014
Day 1
Day 2 ...
*/
} ...
]
}
Referenced solution:
Users:{
name:
surname:
monthlyReports: [
id_reportMonth1, id_reportMonth2, ...
]
}
MonthlyReport: {
id:
month:
dailyReport: [{
day: 1
singleReport: [
{ report1 }, { report2 } ...
]
},
{
} ....
]
}
For single user, i need to retrive single daily report, monthly report, and total report.
I think that in embedded solution, querying is more simple, but create large object in a long period.
Another possibility:
Create 3 referenced collection:
User, monthlyReport, dailyReport.
What is the better way to do it?
Someone has suggested?

Answer 1

Mongo wrote an excellent 3 parts blog post about it: http://blog.mongodb.org/post/87200945828/6-rules-of-thumb-for-mongodb-schema-design-part-1
Bottom line: it depends on the use.
You need to consider two factors (ref: mongodb blog post) :
Will the entities on the “N” side of the One-to-N ever need to stand alone?
What is the cardinality of the relationship: is it one-to-few; one-to-many; or one-to-squillions?
Based on these factors, you can pick one of the three basic One-to-N schema designs:
Embed the N side if the cardinality is one-to-few and there is no
need to access the embedded object outside the context of the parent
object
Use an array of references to the N-side objects if the cardinality
is one-to-many or if the N-side objects should stand alone for any
reasons
Use a reference to the One-side in the N-side objects if the
cardinality is one-to-squillions
Hope this helps.