4

I have no experience with NoSQL. So, I think, if I just try to ask about the code, my question can be incorrect. Instead, let me explain my problem.

Suppose I have e-store. I have catalogs 

Catalogs = new Mongo.Collection('catalogs);

and products in that catalogs

Products = new Mongo.Collection('products');

Then, people add there orders to temporary collection

Order = new Mongo.Collection();

Then, people submit their comments, phone, etc and order. I save it to collection Operations:

Operations.insert({
  phone: "phone",
  comment: "comment",
  etc: "etc"
  savedOrder: Order //<- Array, right? Or Object will be better?
});

Nice, but when i want to get stats by every product, in what Operations product have used. How can I search thru my Operations and find every operation with that product?

Or this way is bad? How real pro's made this in real world?

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3 Answers 3

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7

If I understand it well, here is a sample document as stored in your Operation collection:

{
  clientRef: "john-001",
  phone: "12345678",
  other: "etc.",
  savedOrder: {
      "someMetadataAboutOrder": "...",
      "lines" : [
          { qty: 1, itemRef: "XYZ001", unitPriceInCts: 1050, desc: "USB Pen Drive 8G" },
          { qty: 1, itemRef: "ABC002", unitPriceInCts: 19995, desc: "Entry level motherboard" },
      ]
  }
},
{
  clientRef: "paul-002",
  phone: null,
  other: "etc.",
  savedOrder: {
      "someMetadataAboutOrder": "...",
      "lines" : [
          { qty: 3, itemRef: "XYZ001", unitPriceInCts: 950, desc: "USB Pen Drive 8G" },
      ]
  }
},

Given that, to find all operations having item reference XYZ001 you simply have to query:

> db.operations.find({"savedOrder.lines.itemRef":"XYZ001"})

This will return the whole document. If instead you are only interested in the client reference (and operation _id), you will use a projection as an extra argument to find:

> db.operations.find({"savedOrder.lines.itemRef":"XYZ001"}, {"clientRef": 1})
{ "_id" : ObjectId("556f07b5d5f2fb3f94b8c179"), "clientRef" : "john-001" }
{ "_id" : ObjectId("556f07b5d5f2fb3f94b8c17a"), "clientRef" : "paul-002" }

If you need to perform multi-documents (incl. multi-embedded documents) operations, you should take a look at the aggregation framework:

For example, to calculate the total of an order:

> db.operations.aggregate([
  {$match: { "_id" : ObjectId("556f07b5d5f2fb3f94b8c179") }},
  {$unwind: "$savedOrder.lines" },
  {$group: { _id: "$_id", 
             total: {$sum: {$multiply: ["$savedOrder.lines.qty", 
                                        "$savedOrder.lines.unitPriceInCts"]}}
  }}
])
{ "_id" : ObjectId("556f07b5d5f2fb3f94b8c179"), "total" : 21045 }
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1 Comment

Touch of Master. Thank you, Sylvain, you way is certainly better. With my little Mongo experience, even simple things puzzles me. :)
1

I'm an eternal newbie, but since no answer is posted, I'll give it a try.

First, start by installing robomongo or a similar software, it will allow you to have a look at your collections directly in mongoDB (btw, the default port is 3001)

The way I deal with your kind of problem is by using the _id field. It is a field automatically generated by mongoDB, and you can safely use it as an ID for any item in your collections.

Your catalog collection should have a string array field called product where you find all your products collection items _id. Same thing for the operations: if an order is an array of products _id, you can do the same and store this array of products _id in your savedOrder field. Feel free to add more fields in savedOrder if necessary, e.g. you make an array of objects products with additional fields such as discount.

Concerning your queries code, I assume you will find all you need on the web as soon as you figure out what your structure is.

For example, if you have a product array in your savedorder array, you can pull it out like that:

Operations.find({_id: "your operation ID"},{"savedOrder.products":1)

Basically, you ask for all the products _id in a specific operation. If you have several savedOrders in only one operation, you can specify too the savedOrder _id, if you used the one you had in your local collection.

Operations.find({_id: "your_operation_ID", "savedOrder._id": "your_savedOrder_ID"},{"savedOrder.products":1)

ps: to bad-ass coders here, if I'm doing it wrong, please tell me.

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Thank you very much, Billy! I do not quite understand how to apply your advice, but you gave me idea :)
0

I find an answer :) Of course, this is not a reveal for real professionals, but is a big step for me. Maybe my experience someone find useful. All magic in using correct mongo operators. Let solve this problem in pseudocode.

We have a structure like this:

Operations:
  1. Operation: {
    _id: <- Mongo create this unique for us
    phone: "phone1",
    comment: "comment1",
    savedOrder: [
    {
      _id: <- and again
      productId: <- whe should save our product ID from 'products' 
      name: "Banana",
      quantity: 100
    },
    {
      _id:,
      productId: <- Another ID, that we should save if order 
      name: "apple",
      quantity: 50
    }
    ]

And if we want to know, in what Operation user take "banana", we should use mongoDB operator"elemMatch" in Mongo docs

db.getCollection('operations').find({}, {savedOrder: {$elemMatch:{productId: "f5mhs8c2pLnNNiC5v"}}});

In simple, we get documents our saved order have products with id that we want to find. I don't know is it the best way, but it works for me :) Thank you!

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1 Comment

From a database perspective, I don't think you need an _id in your embedded documents here, as the productId should be sufficient to differential the various order lines (you don't need two lines for the same productId, don't you ?)

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