You call the `index` method on your `Schema` object to do that as shown [here][1].  For your case it would be something like:

    mySchema.index({field1: 1, field2: 1}, {unique: true});


  [1]: http://mongoosejs.com/docs/guide.html#indexes

Defining indexes at the schema level is necessary when creating compound indexes.

    animalSchema.index({ name: 1, type: -1 });

Reference: http://mongoosejs.com/docs/guide.html#indexes

        Following command can be used to create compound index for nested json:
        db.ACCOUNT_collection.createIndex({&quot;account.id&quot;:1,&quot;account.customerId&quot;:1},{unique:1}) 
    Mongo json structure is like :
    {&quot;_id&quot;:&quot;648738&quot;
     &quot;account&quot;: { 
        &quot;id&quot;: &quot;123&quot;,
        &quot;customerId&quot;: 7879,
        &quot;name&quot;: &quot;test&quot;
       ..
       ..
    
      }
    }

I have tested with sample data it is perfectly working as expected.

By the way, the accepted answer is wrong, as per https://stackoverflow.com/a/52553550/129300 you should wrap the field names in single quotes, ie:

    mySchema.index({&#39;field1&#39;: 1, &#39;field2&#39;: 1}, {unique: true});

Happy Day!

I have a data frame with a column called `&quot;Date&quot;` and want all the values from this column to have the same value (the year only). Example:

    City     Date
    Paris    01/04/2004
    Lisbon   01/09/2004
    Madrid   2004
    Pekin    31/2004

What I want is:

    City     Date
    Paris    2004
    Lisbon   2004
    Madrid   2004
    Pekin    2004

Here is my code:

    fr61_70xls = pd.ExcelFile(&#39;AMADEUS FRANCE 1961-1970.xlsx&#39;)
    
    #Here we import the individual sheets and clean the sheets    
    years=([&#39;1961&#39;,&#39;1962&#39;,&#39;1963&#39;,&#39;1964&#39;,&#39;1965&#39;,&#39;1966&#39;,&#39;1967&#39;,&#39;1968&#39;,&#39;1969&#39;,&#39;1970&#39;])

    fr={}
    
    header=([&#39;City&#39;,&#39;Country&#39;,&#39;NACE&#39;,&#39;Cons&#39;,&#39;Last_year&#39;,&#39;Op_Rev_EUR_Last_avail_yr&#39;,&#39;BvD_Indep_Indic&#39;,&#39;GUO_Name&#39;,&#39;Legal_status&#39;,&#39;Date_of_incorporation&#39;,&#39;Legal_status_date&#39;])
        
    for year in years:
        # save every sheet in variable fr[&#39;1961&#39;], fr[&#39;1962&#39;] and so on
        fr[year]=fr61_70xls.parse(year,header=0,parse_cols=10)
        fr[year].columns=header
        # drop the entire Legal status date column
        fr[year]=fr[year].drop([&#39;Legal_status_date&#39;,&#39;Date_of_incorporation&#39;],axis=1)
        # drop every row where GUO Name is empty
        fr[year]=fr[year].dropna(axis=0,how=&#39;all&#39;,subset=[[&#39;GUO_Name&#39;]])
        fr[year]=fr[year].set_index([&#39;GUO_Name&#39;,&#39;Date_of_incorporation&#39;])

*It happens that in my DataFrames, called for example `fr[&#39;1961&#39;]` the values of `Date_of_incorporation` can be anything (strings, integer, and so on), so maybe it would be best to completely erase this column and then attach another column with only the year to the DataFrames?*

Pandas: how to change all the values of a column?

Assume I have an object:

    var obj = {
      foo:&quot;bar&quot;,
      fizz:&quot;buzz&quot;
    };

I need to access a property of that object dynamically like so:

    var objSetter = function(prop,val){
      obj[prop] = val;
    }

No problems there, except for that `prop` needs to be case insensitive in case the property name is passed into the function as, say, `Foo` instead of `foo`.

So how can I point to an object&#39;s property by name without regard to case?  I would like to avoid iterating the entire object if possible.

Access JavaScript property case-insensitively?

I&#39;m trying to find documentation, to no avail, on how to create multi-field indexes in Mongoosejs. In particular I have two fields that need to be indexed and unique. What is an example mongoose schema that indexes two fields together?

Creating Multifield Indexes in Mongoose / MongoDB

<p>I'm trying to find documentation, to no avail, on how to create multi-field indexes in Mongoosejs. In particular I have two fields that need to be indexed and unique. What is an example mongoose schema that indexes two fields together?</p>


I have a lot of mongodb documents in a collection of the form:

    {
    ....
    &quot;URL&quot;:&quot;www.abc.com/helloWorldt/...&quot;
    .....
    }

I want to replace `helloWorldt` with `helloWorld` to get:

    {
    ....
    &quot;URL&quot;:&quot;www.abc.com/helloWorld/...&quot;
    .....
    }

How can I achieve this for all documents in my collection?


How to replace substring in mongodb document

Say, I have a document like this..

    &quot;ID&quot; : &quot;fruit1&quot;,
    &quot;Keys&quot; : [[&quot;apple&quot;, &quot;carrot&quot;, &quot;banana&quot;]]

How do I query for Keys = &quot;carrot&quot;. None of the following syntax works.

    db.myColl.results.find({ &quot;Keys&quot; : &quot;carrot&quot; });
    db.myColl.results.find({ &quot;Keys&quot; : [[&quot;carrot&quot;]] });

Following works though, but not helpful.

    db.myColl.results.find({ &quot;Keys&quot; : [[&quot;apple&quot;, &quot;carrot&quot;, &quot;banana]]});

Any pointer to this query will be helpful. Thanks.

Querying an array of arrays in MongoDB

Is there a way to add created_at and `updated_at` fields to a mongoose schema, without having to pass them in everytime new `MyModel()` is called?

The `created_at` field would be a date and only added when a document is created.
The `updated_at` field would be updated with new date whenever `save()` is called on a document.

I have tried this in my schema, but the field does not show up unless I explicitly add it:

    var ItemSchema = new Schema({
        name    : { type: String, required: true, trim: true },
        created_at    : { type: Date, required: true, default: Date.now }
    });



add created_at and updated_at fields to mongoose schemas

&lt;!-- language-all: lang-js --&gt;

Is there an explain function for the Aggregation framework in MongoDB? I can&#39;t see it in the documentation.

If not is there some other way to check, how a query performs within the aggregation framework?

I know with find you just do 

    db.collection.find().explain()

But with the aggregation framework I get an error

    db.collection.aggregate(
    	{ $project : { &quot;Tags._id&quot; : 1 }},
    	{ $unwind : &quot;$Tags&quot; },
    	{ $match: {$or: [{&quot;Tags._id&quot;:&quot;tag1&quot;},{&quot;Tags._id&quot;:&quot;tag2&quot;}]}},
    	{ 
    		$group: 
    		{ 
    			_id : { id: &quot;$_id&quot;},
    			&quot;count&quot;: { $sum:1 } 
    		}
    	},
    	{ $sort: {&quot;count&quot;:-1}}
    ).explain()

Mongodb Explain for Aggregation framework

This question is about making an architectural choice prior to delving into the details of experimentation and implementation. It&#39;s about the suitability, in scalability and performance terms, of elasticsearch v.s. MongoDB, for a somewhat specific purpose. 

Hypothetically both store data objects that have fields and values, and allow querying that body of objects. So presumably filtering out subsets of the objects according to fields selected ad-hoc, is something fit for both. 

My application will revolve around selecting objects according to criteria.
It would select objects by filtering simultaneously by more than a single field, put differently, its query filtering criteria would typically comprise anywhere between 1 and 5 fields, maybe more in some cases. Whereas the fields chosen as filters would be a subset of a much larger amount of fields. Picture some 20 field names existing, and each query is an attempt to filter the objects by few fields out of those overall 20 fields (It can be less or more than 20 overall field names existing, I just used this number to demonstrate the ratio of fields to fields used as filters in every discrete query). The filtering can be by the existence of the chosen fields, as well as by the field values, e.g. filtering out objects that have field A, and their field B is between x and y, and their field C is equal to w. 

My application will be continuously doing this sort of filtering, whereas there would be nothing or very little constant in terms of which fields are used for the filtering at any moment. Perhaps in elasticsearch indexes need to be defined, but maybe even without indexes speed is at par with that of MongoDB. 

As per the data getting into the store, there are no special details about that.. the objects would be almost never changed after having been inserted. Perhaps old objects would need to be dropped, I&#39;d like to assume both data stores support expire deleting stuff internally or by an application made query. (Less frequently, objects that fit a certain query would need to be dropped as well).

What do you think?
And, have you experimented this aspect?

I am interested in the performance and the scalability of it, of each of the two data stores, for this kind of task. This is the sort of an architectural desing question, and details of store-specific options or query cornerstones that should make it well architected are welcome as a demonstration of a fully thought-out suggestion.

Thanks!

elasticsearch v.s. MongoDB for filtering application

Just a simple query, for example with a double ref in the model.

**Schema / Model**

    var OrderSchema = new Schema({

        user: {
            type    : Schema.Types.ObjectId,
            ref     : &#39;User&#39;,
            required: true
        },

        meal: {
            type    : Schema.Types.ObjectId,
            ref     : &#39;Meal&#39;,
            required: true
        },
    });

    var OrderModel = db.model(&#39;Order&#39;, OrderSchema);


**Query**

    OrderModel.find()
        .populate(&#39;user&#39;) // works
        .populate(&#39;meal&#39;) // dont works
        .exec(function (err, results) {
             // callback
        });

I already tried something like

    .populate(&#39;user meal&#39;)
    .populate([&#39;user&#39;, &#39;meal&#39;])

In fact only one of the populates works.

So, how do is get two populates working ? 

Multiple populates - mongoosejs

I am adding a comment to an item.comments list. I need to get the comment.created_by user data before I output it in the response. How should I do this?


		Item.findById(req.param(&#39;itemid&#39;), function(err, item){
			var comment = item.comments.create({
				body: req.body.body
				, created_by: logged_in_user
			});

			item.comments.push(comment);

			item.save(function(err, item){
				res.json({
					status: &#39;success&#39;,
					message: &quot;You have commented on this item&quot;,

    //how do i populate comment.created_by here???

					comment: item.comments.id(comment._id)
				});
			}); //end item.save
		}); //end item.find


I need to populate the comment.created_by field here in my res.json output:

					comment: item.comments.id(comment._id)

comment.created_by is a user reference in my mongoose CommentSchema. It currently is only giving me a user id, I need it populated with all the user data, except for password and salt fields.

Here is the schema as people have asked:

    var CommentSchema = new Schema({
        body          : { type: String, required: true }
      , created_by    : { type: Schema.ObjectId, ref: &#39;User&#39;, index: true }
      , created_at    : { type: Date }
      , updated_at    : { type: Date }
    });
    
    var ItemSchema = new Schema({
        name    : { type: String, required: true, trim: true }
      , created_by  : { type: Schema.ObjectId, ref: &#39;User&#39;, index: true }
      , comments  : [CommentSchema]
    });



How to populate a sub-document in mongoose after creating it?

IN nodejs, with mongodb, mongoosejs as orm

I am doing this

I have a model, User

    User.findOne({username:&#39;someusername&#39;}).exec(function(err,user){
    console.log(user) //this gives full object with something like {_id:234234dfdfg,username:&#39;someusername&#39;}
    //but

    console.log(user._id) //give undefined.
    })

Why? And how to get the _id to string then?

nodejs mongodb object id to string

I want to combine two OR-queries with AND in Monoose, like in this SQL statement:

    SELECT * FROM ... WHERE (a = 1 OR b = 1) AND (c=1 OR d=1)

I tried this in a NodeJS module which only gets the model object from the main application:

    /********** Main application ***********/
    var query = MyModel.find({});
    myModule1.addCondition(query);
    myModule2.addCondition(query);
    query.exec(...)

    /************ myModule1 ***************/
    exports.addCondition = function(query) {
      query.or({a: 1}, {b: 1});
    }

    /************ myModule2 ***************/
    exports.addCondition = function(query) {
      query.or({c: 1}, {d: 1});
    }

But this doesn&#39;t work, all OR-conditions will get joined together like in this SQL statement:

    SELECT * FROM ... WHERE a = 1 OR b = 1 OR c=1 OR d=1

How can I combine the two conditions of `myModule1` and `myModule2` with AND in Mongoose?

Content Type	Original Author	Original Content on Stackoverflow
Question	Dan	View Question on Stackoverflow
Solution 1 - Mongodb	JohnnyHK	View Answer on Stackoverflow
Solution 2 - Mongodb	Krumb	View Answer on Stackoverflow
Solution 3 - Mongodb	Rajeev Rathor	View Answer on Stackoverflow
Solution 4 - Mongodb	Fer Martin	View Answer on Stackoverflow

Creating Multifield Indexes in Mongoose / MongoDB

Mongodb Problem Overview

Mongodb Solutions

Solution 1 - Mongodb

Solution 2 - Mongodb

Solution 3 - Mongodb

Solution 4 - Mongodb

Access JavaScript property case-insensitively?

Pandas: how to change all the values of a column?

Attributions