Meteor/MongoDB Reference specific subdocument from another document - mongodb

Question

I'm working on prototyping a note-taking application in Meteor; functional requirements include:
users have access to shared notes
notes contain distinct sections
each user needs to be able to add notations to notes/sections
notations can be preserved over time (e.g. add to existing notations without updating or deleting previously created notation)
notations should be private between users
Given the above, each document has a data key that contains the array of subdocuments - each section of the note. Something like this:
{
"_id" : ObjectId("someObjectID"),
"owner" : "Q5mpJZnAtFN5EMWT9",
"createdAt" : "2018-01-05T22:56:03.257Z",
"updatedAt" : "2018-01-06T12:07:03.123Z",
"parent" : null,
"title" : "Note Title",
"data" : [
{
"date" : "2018-01-05T22:56:03.257Z",
"title" : "Section 1 Title",
"text" : "Section content goes here..."
},
{
"date" : "2018-01-05T22:56:03.257Z",
"title" : "Section 2 Title",
"text" : "Section content goes here..."
}
]
}
For the main notes documents, the data array stores the sections as subdocuments; for user notations, the data array stores their personal notations as subdocuments. My thinking is to use the parent key to distinguish between shared notes and user notations:
parent : null for "top level", shared notes
something like parent : "yG8xrh6KiZXv7e8MD" to point back to the "top level" note or subdocument for user notations. (Hopefully this makes sense).
Two questions. First and foremost - is this a valid design?
If it IS a valid design, how do I then reference a specific subdocument? For example, in the above document, if a user wants to add a notation to Section 2 only? Can I add an _id to the subdocument and then use that value for the parent key in the notation document?

Answer 1

This not the complete solution, but just an example:
I would do it something like this. I'd modify your document a bit, adding notations field in every section:
{
"_id" : ObjectId("someObjectID"),
"owner" : "Q5mpJZnAtFN5EMWT9",
"createdAt" : "2018-01-05T22:56:03.257Z",
"updatedAt" : "2018-01-06T12:07:03.123Z",
"parent" : null,
"title" : "Note Title",
"data" : [
{
"date" : "2018-01-05T22:56:03.257Z",
"title" : "Section 1 Title",
"text" : "Section content goes here...",
"notations": [
{
_id: "some id",
version:1
userId: "fsajksffhj",
date: "2018-01-05T22:56:06",
note: "some note about this sectioon"
},
{
_id: "some id2",
version:1,
userId: "fsajksffhj",
date: "2018-01-05T22:56:06",
note: "some note about this sectioon"
},
{
_id: "some id1",
version:1,
userId: "fsajksffhj",
date: "2018-02-06T00:56:06",
note: "edited the first notation"
}
]
},
{
"date" : "2018-01-05T22:56:03.257Z",
"title" : "Section 2 Title",
"text" : "Section content goes here..."
}
]
}
notations should be private between users
This is harder part. I'd use Meteor Methods to do this. Another way could be to use MongoDB's aggregation functionality with match, unwind, re-match, group and create document again. You are using reactivity if using either of these.
Meteor.methods({
'notes.singleNote: function(noteId, notationsUserId) {
check(noteId, String);
check(notationsUserId);
let note = Notes.findOne(noteId);
// remove other users' notations
note.data = note.data.map(function(data) {
if (data.notations) {
data.notations = data.notations.filter(function(d) {
return d.userId === notationsUserId;
});
}
return data
});
});
return note;
}
});