How to access data from a nested array structured collection

Question

I have the following structure in my MongoDB . I have a nested structure of my collection named chains which is shown below . I am trying to access options of a particular date as shown below which is 2015-01-17 in my case .

db.chains.find({ "symbol" : "UBSC" ,"option_exp.expiration_dt" : "2015-01-17"}).pretty()

But the following query above is returning me all the data related to that Symbol .

{
        "_id" : ObjectId("52000a90d293b0e4134e8c35"),
        "symbol" : "UBSC",
        "option_exp" : [
                {
                        "expiration_dt" : "2015-01-17",
                          "options" : [
                                {
                                        "mult" : "10"
                                },
                                {
                                        "mult" : "10"
                                }
                        ]
                    },
                        {
                        "expiration_dt" : "2014-01-18",
                        "options" : [
                                {

                                        "prem_mult" : "10"
                                },
                                {
                                        "prem_mult" : "10"
                                }

           }
                        ]
                }
        ],
}

This is the way i was trying to access through java

BasicDBObject query = new BasicDBObject();
query.append("symbol", "UBSC");
query.append("option_exp.expiration_dt", "2015-01-17");

Could anybody please help me as how to access data of a particular date .

Sergey Berezovskiy · Accepted Answer · 2013-08-21 13:22:17Z

3

Use $elemMatch to limit content of option_exp array field that is included in result:

db.chains.find({symbol : "UBSC" ,"option_exp.expiration_dt" : "2015-01-17"}, 
               {option_exp: {$elemMatch: {expiration_dt: "2015-01-17"}}})

This will select documents which have symbol equal to "UBSC" and option_exp array items with expiration_dt equal to "2015-01-17". Then we limit option_exp array content to items which have required expiration date (otherwise whole document will all option_exp items will be returned).

edited Aug 21, 2013 at 13:22

answered Aug 21, 2013 at 13:16

Sergey Berezovskiy

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9 Comments

Pawan Over a year ago

hey thanks i tried this option you mentioned , but unfortunately i was getting this below error error: { "$err" : "Unsupported projection option: $elemMatch", "code" : 13097 } , i was using mongo1.6 version

Pawan Over a year ago

I see that elemMatch has got suppourt since version 2.2 , so is there any other alternative to achieve this .

Ross Over a year ago

Prior to 2.2 you'd have to do it in your code after the matched document has come over the wire.

Sergey Berezovskiy Over a year ago

@PreethiJain is it possible that several items with same expiration_dt will be in array? If all dates are different, then you can use operator $: {"option_exp.$":1} but it returns only first matching item from array

Sergey Berezovskiy Over a year ago

@PreethiJain sorry, but I don't know other way to do that in mongo 1.6. You can change schema to have only one item per date (e.g. let it contain all options) - thus $ will work, you can update mongo to 2.2 to use $elemMatch, or you can filter in-memory

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