**UPDATE** Newer versions of Compass now support querying ObjectId similar to how they would be queried via the mongo shell (the `$oid` syntax will *not* work in these newer versions):

    {_id: ObjectId(&#39;58f8085dc1840e050034d98f&#39;)}


If you&#39;re using an older version before 1.10.x you, enter the following into the query box:
  
    {&quot;_id&quot;:{&quot;$oid&quot;:&quot;58f8085dc1840e050034d98f&quot;}}

It&#39;s also worth pointing out that in the UI you can click on one of the _ids and it will auto-populate the query box with the query based on what you clicked. You can also shift+click on multiple fields to create compound (and-ed) query criteria, or you can click and drag to select a range.


Skip and Limit are support for versions &gt;= 1.8.x **does** support skip and limit when browsing under the Documents tab. Click the &quot;Options&quot; button on the right side of the Query Bar. See the [Query Bar][1] docs for illustration and details.

The Schema tab only supports limit, as this will do a sampling of documents and skip doesn&#39;t really make sense in that context.

In order to click on the _ids you need to be on the [Schema][2] tab. If your _ids are of type ObjectId, the visualization of the distribution will appear as a date range and you can drag over one or more lines to populate the query based on _id. If your _ids are some other type, some portion of them will display individually and you can click, drag, or shift-click over them.

  [1]: https://docs.mongodb.com/compass/master/query-bar/
  [2]: https://docs.mongodb.com/compass/master/schema/

The current version of MongoDB Compass (1.10.5) no longer appears to support `$oid`, but it does work with a standard query: `{&quot;_id&quot;:ObjectId(&quot;5a028baa2dc80f2e26a8ed63&quot;)}`

{&quot;_id&quot;:ObjectId(&quot;5f8344e2a00ed7f6172a7184&quot;)}

    {module_id: ObjectId(&#39;5cee65f283774d3470fc01cc&#39;)}

**Search Result:**
[![search result][1]][1]


  [1]: https://i.stack.imgur.com/s8uBW.png

I&#39;m deciding on whether to use [Moshi by square][1] or Gson to serialize and deserialize model data.   

one thing i always did not like about Gson is i think it uses reflection which can be slow on android? Does Moshi use reflection also?  

What are some of the pros and cons of moshi vs Gson?

I see them as similar. take for example this statement that creates a `typeAdapter:`

    class CardAdapter {
      @ToJson String toJson(Card card) {
        return card.rank + card.suit.name().substring(0, 1);
      }
    
      @FromJson Card fromJson(String card) {
        if (card.length() != 2) throw new JsonDataException(&quot;Unknown card: &quot; + card);
    
        char rank = card.charAt(0);
        switch (card.charAt(1)) {
          case &#39;C&#39;: return new Card(rank, Suit.CLUBS);
          case &#39;D&#39;: return new Card(rank, Suit.DIAMONDS);
          case &#39;H&#39;: return new Card(rank, Suit.HEARTS);
          case &#39;S&#39;: return new Card(rank, Suit.SPADES);
          default: throw new JsonDataException(&quot;unknown suit: &quot; + card);
        }
      }
    }

and to use it register it just like in gson:

    Moshi moshi = new Moshi.Builder()
    .add(new CardAdapter())
    .build();

I guess the advantages would be the annotation being used in the typeAdapter. I&#39;m looking to find out if there are any performance gains if I switch to Moshi. 

  [1]: https://github.com/square/moshi


Moshi vs Gson in android

After searching for some references to figure it out, -unfortunately- I could not find useful -and simple- description about understanding the differences between `throws` and `rethrows`. It is kind of confusing when try to understand how we should use them.

I would mention that I am kind of familiar with the -default- `throws` with its simplest form for propagating an error, as follows:


    enum CustomError: Error {
        case potato
        case tomato
    }
    
    func throwCustomError(_ string: String) throws {
        if string.lowercased().trimmingCharacters(in: .whitespaces) == &quot;potato&quot; {
            throw CustomError.potato
        }
        
        if string.lowercased().trimmingCharacters(in: .whitespaces) == &quot;tomato&quot; {
            throw CustomError.tomato
        }
    }
    
    do {
        try throwCustomError(&quot;potato&quot;)
    } catch let error as CustomError {
        switch error {
        case .potato:
            print(&quot;potatos catched&quot;) // potatos catched
        case .tomato:
            print(&quot;tomato catched&quot;)
        }
    }

So far so good, but the problem arises when:

    func throwCustomError(function:(String) throws -&gt; ()) throws {
        try function(&quot;throws string&quot;)
    }
    
    func rethrowCustomError(function:(String) throws -&gt; ()) rethrows {
        try function(&quot;rethrows string&quot;)
    }
    
    rethrowCustomError { string in
        print(string) // rethrows string
    }
    
    try throwCustomError { string in
        print(string) // throws string
    }

what I know so far is when calling a function that `throws` it has to be handled by a `try`, unlike the `rethrows`. So what?! What is logic that we should follow when deciding to use `throws` or `rethrows`?

What are the differences between throws and rethrows in Swift?

How does one use Mongo Compass and search by ObjectID? I&#39;ve been searching for the documentation for this but haven&#39;t been successful with anything. I have tried:

    { &quot;_id&quot; : &quot;58f8085dc1840e050034d98f&quot; }
    
    { &quot;$oid&quot; : &quot;58f8085dc1840e050034d98f&quot; }
    
    { &quot;id&quot; : &quot;58f8085dc1840e050034d98f&quot; }


None of those seem to work and it&#39;s getting quite frustrating. Also, sidenote - is it possible to set the skip/limit when displaying documents in Compass?

Thanks in advance!

Searching by ObjectId on Mongo Compass

How does one use Mongo Compass and search by ObjectID? I've been searching for the documentation for this but haven't been successful with anything. I have tried:
<pre><code class="hljs language-bash">{ "_id" : "58f8085dc1840e050034d98f" }

{ "$oid" : "58f8085dc1840e050034d98f" }

{ "id" : "58f8085dc1840e050034d98f" }
</code></pre>
None of those seem to work and it's getting quite frustrating. Also, sidenote - is it possible to set the skip/limit when displaying documents in Compass?
Thanks in advance!

I have a query like this (simplified):

&lt;!-- language-all: lang-javascript --&gt;

    db.collection.aggregate([
      { $match: { main_id: ObjectId(&quot;58f0f67f50c6af16709fd2c7&quot;) } }, 
      {
        $group: {
          _id: &quot;$name&quot;,
          count: { $sum: 1 },
          sum: { $sum: { $add: [&quot;$P31&quot;, &quot;$P32&quot;] } }
        }
      }
    ])

I do this query from Java, and I want to map it on my class, but I don&#39;t want `_id` to be mapped on `name` field. Because if I do something like this:

&lt;!-- language-all: lang-java --&gt;

    @JsonProperty(&quot;_id&quot;)
    private String name;

then when I save this data back to mongo (after some modification) the data is saved with name as `_id` while I want a real Id to be generated.

So, how can I **rename** `_id` after `$group` operation?


Is it possible to rename _id field after mongo&#39;s group aggregation?

I am trying to post data to database that I have created on mLab and I am getting this error but I don&#39;t know whats going wrong.I also have read previously asked question on this topic but I am not able to solve my error as I am new to this. So here I am posting the code which I am trying to implement and It is taken from this tutorial [https://medium.freecodecamp.com/building-a-simple-node-js-api-in-under-30-minutes-a07ea9e390d2][1]. 

server.js

    const express = require(&#39;express&#39;);
    const MongoClient = require(&#39;mongodb&#39;).MongoClient;
    const bodyParser = require(&#39;body-parser&#39;);
    
    const db = require(&#39;./config/db&#39;);
    
    
    const app = express();
    
    const port = 8000;
    
    app.use(bodyParser.urlencoded({extened:true}));
    
    
    MongoClient.connect(db.url,(err,database) =&gt;{
    	
    	if (err) return console.log(err)
    	require(&#39;./app/routes&#39;)(app,{});
    	app.listen(port,() =&gt; {
    		console.log(&quot;We are live on&quot;+port);	
    	});
    
    })

db.js 

    module.exports = {
      url : &quot;mongodb://JayTanna:Jay12345@ds147510.mlab.com:47510/testing&quot;
    };

index.js 

    const noteroutes = require(&#39;./note_routes&#39;);
    
    module.exports = function(app,db)
    {
    	noteroutes(app,db);
    	
    };

note_routes.js

    module.exports = function(app, db) {
      app.post(&#39;/notes&#39;, (req, res) =&gt; {
        const note = { text: req.body.body, title: req.body.title };
        db.collection(&#39;notes&#39;).insert(note, (err, result) =&gt; {
          if (err) { 
            res.send({ &#39;error&#39;: &#39;An error has occurred&#39; }); 
          } else {
            res.send(result.ops[0]);
          }
        });
      });
    };


  [1]: https://medium.freecodecamp.com/building-a-simple-node-js-api-in-under-30-minutes-a07ea9e390d2

TypeError: db.collection is not a function

This is the code I use to connect to my database:

    private connectDatabase(databaseUri: string): Promise&lt;Mongoose.Connection&gt; {
        return Mongoose.connect(databaseUri).then(() =&gt; {
            debug(&#39;Connected to MongoDB at %O&#39;, databaseUri);
            return Mongoose.connection;
        });
    }


Today I updated Mongoose to version 4.11.0 and I got this warning when running my tests:

    (node:4138) DeprecationWarning: `open()` is deprecated in mongoose &gt;= 4.11.0,
    use `openUri()` instead, or set the `useMongoClient` option if using `connect()`
    or `createConnection()`

I can&#39;t find any information on how to &quot;set useMongoClient&quot;.

Do you guys know how to?




How to set useMongoClient (Mongoose 4.11.0)?

**Env:**
 
 - MongoDB (3.2.0) with Mongoose


----------


**Collection:**

- users


----------


**Text Index creation:**


      BasicDBObject keys = new BasicDBObject();
      keys.put(&quot;name&quot;,&quot;text&quot;);
    
      BasicDBObject options = new BasicDBObject();
      options.put(&quot;name&quot;, &quot;userTextSearch&quot;);
      options.put(&quot;unique&quot;, Boolean.FALSE);
      options.put(&quot;background&quot;, Boolean.TRUE);
      
      userCollection.createIndex(keys, options); // using MongoTemplate


----------


**Document:**

- {&quot;name&quot;:&quot;LEONEL&quot;}


----------


**Queries:**

- `db.users.find( { &quot;$text&quot; : { &quot;$search&quot; : &quot;LEONEL&quot; } } )` =&gt; FOUND
- `db.users.find( { &quot;$text&quot; : { &quot;$search&quot; : &quot;leonel&quot; } } )` =&gt; FOUND (search caseSensitive is false)
- `db.users.find( { &quot;$text&quot; : { &quot;$search&quot; : &quot;LEON&#201;L&quot; } } )` =&gt; FOUND (search with diacriticSensitive is false)
- `db.users.find( { &quot;$text&quot; : { &quot;$search&quot; : &quot;LEONE&quot; } } )` =&gt; FOUND (Partial search)
- `db.users.find( { &quot;$text&quot; : { &quot;$search&quot; : &quot;LEO&quot; } } )` =&gt; NOT FOUND (Partial search)
- `db.users.find( { &quot;$text&quot; : { &quot;$search&quot; : &quot;L&quot; } } )` =&gt; NOT FOUND (Partial search)


Any idea why I get 0 results using as query &quot;LEO&quot; or &quot;L&quot;?

Regex with Text Index Search is not allowed.


    db.getCollection(&#39;users&#39;)
         .find( { &quot;$text&quot; : { &quot;$search&quot; : &quot;/LEO/i&quot;, 
                              &quot;$caseSensitive&quot;: false, 
                              &quot;$diacriticSensitive&quot;: false }} )
         .count() // 0 results

    db.getCollection(&#39;users&#39;)
         .find( { &quot;$text&quot; : { &quot;$search&quot; : &quot;LEO&quot;, 
                              &quot;$caseSensitive&quot;: false, 
                              &quot;$diacriticSensitive&quot;: false }} )
    .count() // 0 results


----------


**MongoDB Documentation:**

- [Text Search][1]
- [$text][2]
- [Text Indexes][3]
- [Improve Text Indexes to support partial word match][4]


  [1]: https://docs.mongodb.com/v3.2/text-search/
  [2]: https://docs.mongodb.com/manual/reference/operator/query/text/
  [3]: https://docs.mongodb.com/manual/core/index-text/
  [4]: https://jira.mongodb.org/browse/SERVER-15090

MongoDB Full and Partial Text Search

I&#39;ve tried 

    db.users.remove(*)

Although it returns an error so how do I go about clearing all records?

MongoDB: How To Delete All Records Of A Collection in MongoDB Shell?

I&#39;m looking for an advice about which indexing strategy to use in MongoDb 3.4.  

Let&#39;s suppose we have a *people* collection of documents with the following shape:  

    {
        _id: 10,
        name: &quot;Bob&quot;,
        age: 32,
        profession: &quot;Hacker&quot;
    }

Let&#39;s imagine that a web api to query the collection is exposed and that the only possibile filters are by *name* or by *age*.  
A sample call to the api will be something like:  `http://myAwesomeWebSite/people?name=&quot;Bob&quot;&amp;age=25`

Such a call will be translated in the following query: `db.people.find({name: &quot;Bob&quot;, age: 25})`.  

To better clarify our scenario, consider that: 

 - the field *name* was already in our documents and we already have an index on that field
 - we are going to add the new field *age* due to some new features of our application
 - the database is only accessible via the web api mentioned above and the most important requirement is to expose a super fast web api 
 - all the calls to the web api will apply a filter **on both the fields name and age** (put another way, all the calls to the web api will have the same pattern, which is the one showed above) 

That said, we have to decide which of the following indexes offer the best performance:

 - One compound index: `{name: 1, age: 1}`
 - Two single-field indexes: `{name: 1}` and `{age: 1}`

According to some simple tests, it seems that **the single compound index is much more performant than the two single-field indexes**.  

By executing a single query via the mongo shell, the explain() method suggests that using a single compound index you can query the database nearly ten times faster than using two single fields indexes.  
  
**This difference seems to be less drammatic in a more realistic scenario, where instead of executing a single query via the mongo shell, multiple calls are made to two different urls of a nodejs web application**. Both urls execute a query to the database and return the fetched data as a json array, one using a collection with the single compound index and the other using a collection with two single-field indexes (both collections having exactly the same documents).  
In this test the single compound index still seems to be the best choice in terms of performance, but this time the difference is less marked.  

According to test results, we are considering to use the single compound index approach.  

Does anyone has experience about this topic ? Are we missing any important consideration (maybe some disadvantage of big compound indexes) ?


MongoDB Find performance: single compound index VS two single field indexes

I&#39;m new to MongoDB Compass tool and am trying to update a field in my collection. Please can someone suggest where the update query must be written. Could find no options or panes in the tool to write custom queries be it selection / updation for that matter.

In the Default Window only the selection/projection/restriction options are found.
Any help is much appreciated.

Content Type	Original Author	Original Content on Stackoverflow
Question	aamirl	View Question on Stackoverflow
Solution 1 - Mongodb	helmy	View Answer on Stackoverflow
Solution 2 - Mongodb	jpoveda	View Answer on Stackoverflow
Solution 3 - Mongodb	hosam hemaily	View Answer on Stackoverflow
Solution 4 - Mongodb	Kishan	View Answer on Stackoverflow

Searching by ObjectId on Mongo Compass

Mongodb Problem Overview

Mongodb Solutions

Solution 1 - Mongodb

Solution 2 - Mongodb

Solution 3 - Mongodb

Solution 4 - Mongodb

What are the differences between throws and rethrows in Swift?

Moshi vs Gson in android

Attributions