Yes, there&#39;s an [`isNew`][1] boolean property on a model instance that indicates that.  Access it as `this.isNew` from your pre save middleware.


  [1]: http://mongoosejs.com/docs/api.html#document_Document-isNew

    var MySchema = new Schema({...});

    MySchema.pre(&#39;save&#39;, function(next) {
        if (this.isNew) {
            // Hooray !
        }
        next();
    });

I&#39;m trying to wrap my head around the TPL, the new `async` / `await` features in C# 5, and the mysteries of `TaskCompletionSource`.

One thing that isn&#39;t clear to me is when to use `SetResult`, `SetException`, and `SetCancel` versus `TrySetResult`, `TrySetException` and `TrySetCancel`.

This is what MSDN has to say:

&gt; This operation will return false if the Task&lt;TResult&gt; is already in
&gt; one of the three final states: RanToCompletion, Faulted, or Canceled.
&gt; 
&gt; This method also returns false if the underlying Task&lt;TResult&gt; has
&gt; already been disposed.

Ok, I get that, but it doesn&#39;t really offer any guidance on when or why to use one over the other.  

So, what&#39;s the deal?

TaskCompletionSource : When to use SetResult() versus TrySetResult(), etc

Hey all i am trying to figure out how to go about inserting a new record using the following query:

    SELECT user.id, user.name, user.username, user.email, 
      IF(user.opted_in = 0, &#39;NO&#39;, &#39;YES&#39;) AS optedIn  
    FROM 
      user
      LEFT JOIN user_permission AS userPerm ON user.id = userPerm.user_id
    ORDER BY user.id;

My `INSERT` query so far is this:

    INSERT INTO user 
    SELECT * 
    FROM user 
      LEFT JOIN user_permission AS userPerm ON user.id = userPerm.user_id;

However, i  am not sure how to do `VALUE(&#39;&#39;,&#39;&#39;,&#39;&#39;,&#39;&#39;, etc etc)` when using left and inner joins.

So what i am looking to do is this:

`User` table:

    id    | name       | username    | password                 | OptIn
    --------------------------------------------------------------------
    562     Bob Barker   bBarker       BBarker@priceisright.com   1

And also the `user_permission` table

    user_id   | Permission_id
    -------------------------
    562         4

**UPDATE**
So like this?

    INSERT INTO user (name, username, password, email, opted_in) VALUES (&#39;Bbarker&#39;,&#39;Bbarker&#39;,&#39;blahblahblah&#39;,&#39;Bbarker@priceisright.com&#39;,0);
    INSERT INTO user_permission (user_id, permission_id) VALUES (LAST_INSERT_ID(),4);

Insert using LEFT JOIN and INNER JOIN

Is there a way to find out if a record &quot;is new&quot; (has not been save yet) in the pre save callback of mongoose model schema?

Determine if a record &quot;is new&quot; in the pre save callback

<p>Is there a way to find out if a record "is new" (has not been save yet) in the pre save callback of mongoose model schema?</p>


Suppose I have two collections/schemas. One is the Users Schema with username and password fields, then, I have a Blogs Schema that has a reference to the Users Schema in the author field. If I use Mongoose to do something like

    Blogs.findOne({...}).populate(&quot;user&quot;).exec()

I will have the Blog document and the user populated too, but how do I prevent Mongoose/MongoDB from returning the password field? The password field is hashed but it shouldn&#39;t be returned.

I know I can omit the password field and return the rest of the fields in a simple query, but how do I do that with populate. Also, is there any elegant way to do this?

Also, in some situations I do need to get the password field, like when the user wants to login or change the password.

How to protect the password field in Mongoose/MongoDB so it won&#39;t return in a query when I populate collections?

I want to make a HTTP-request using node.js to load some text from a webserver. Since the response can contain much text (some Megabytes) I want to process each text chunk separately. I can achieve this using the following code:

    var req = http.request(reqOptions, function(res) {
        ...
        res.setEncoding(&#39;utf8&#39;);
        res.on(&#39;data&#39;, function(textChunk) {
            // process utf8 text chunk
        });
    });

This seems to work without problems. However I want to support HTTP-compression, so I use zlib:

    var zip = zlib.createUnzip();
    
    // NO res.setEncoding(&#39;utf8&#39;) here since we need the raw bytes for zlib
    res.on(&#39;data&#39;, function(chunk) {
        // do something like checking the number of bytes downloaded
        zip.write(chunk); // give the raw bytes to zlib, s.b.
    });
    
    zip.on(&#39;data&#39;, function(chunk) {
        // convert chunk to utf8 text:
        var textChunk = chunk.toString(&#39;utf8&#39;);
        
        // process utf8 text chunk
    });
    
This can be a problem for multi-byte characters like `&#39;\u00c4&#39;` which consists of two bytes: `0xC3` and `0x84`. If the first byte is covered by the first chunk (`Buffer`) and the second byte by the second chunk then `chunk.toString(&#39;utf8&#39;)` will produce incorrect characters at the end/beginning of the text chunk. How can I avoid this?

Hint: I still need the buffer (more specifically the number of bytes in the buffer) to limit the number of downloaded bytes. So using `res.setEncoding(&#39;utf8&#39;)` like in the first example code above for non-compressed data does not suit my needs.

convert streamed buffers to utf8-string

I&#39;m working with Jade and Express and I would like to use a variable in my include statement. For example:

app.js

    app.get(&#39;/admin&#39;, function (req, res) {
      var Admin = require(&#39;./routes/admin/app&#39;).Admin;

      res.render(Admin.view, {
        title: &#39;Admin&#39;,
        page: &#39;admin&#39;
      });
    });

layout.jade

    - var templates = page + &#39;/templates/&#39;
    
    include templates

When I do this I get the error `EBADF, Bad file descriptor &#39;templates.jade&#39;`

I even tried

    include #{templates}

to no avail.


Use a variable in a Jade include

How do I unzip a gzipped body in a request&#39;s module response?

I have tried several examples around the web but none of them appear to work.

    request(url, function(err, response, body) {
        if(err) {
            handleError(err)
        } else {
            if(response.headers[&#39;content-encoding&#39;] == &#39;gzip&#39;) {    
                // How can I unzip the gzipped string body variable?
                // For instance, this url:
                // http://highsnobiety.com/2012/08/25/norse-projects-fall-2012-lookbook/
                // Throws error:
                // { [Error: incorrect header check] errno: -3, code: &#39;Z_DATA_ERROR&#39; }
                // Yet, browser displays page fine and debugger shows its gzipped
                // And unzipped by browser fine...
                if(response.headers[&#39;content-encoding&#39;] &amp;&amp; response.headers[&#39;content-encoding&#39;].toLowerCase().indexOf(&#39;gzip&#39;) &gt; -1) {	
                    var body = response.body;                    
                    zlib.gunzip(response.body, function(error, data) {
                        if(!error) {
                            response.body = data.toString();
                        } else {
                            console.log(&#39;Error unzipping:&#39;);
                            console.log(error);
                            response.body = body;
                        }
                    });
                }
            }
        }
    }

How do I ungzip (decompress) a NodeJS request&#39;s module gzip response body?

I am creating a node command line interface. It is installed globally and uses a bin file to execute.

I plan to have a command window open at the root directory of the files I am working on and then just run the command however I have been unable to determine the current working directory as `process.cwd()` is returning the directory of the node package. I initially assumed that since the code is being executed using a batch file as a wrapper (that is how bin files can execute without node at the beginning) then it is impossible but coffee-script manages to do it. I took a look at the coffee-script source but couldn&#39;t follow it (not experienced enough).

To test it for yourself create a package with this package.json file:

    {
      &quot;name&quot;: &quot;test-package&quot;,
      &quot;version&quot;: &quot;1.0.0&quot;,
      &quot;bin&quot;: {
        &quot;test-package&quot;:  &quot;./bin/test-package&quot;
      },
      &quot;main&quot;: &quot;/lib/test&quot;
    }

this test-package file in bin:


    #!/usr/bin/env node

    var path = require(&#39;path&#39;);
    var fs   = require(&#39;fs&#39;);
    var lib  = path.join(path.dirname(fs.realpathSync(__filename)), &#39;../lib&#39;);

    require(lib + &#39;/test&#39;);
    
Could anyone shed some light onto this.

and then try and get the command line directory inside lib/test.


Determine command line working directory when running node bin script

I wonder how mongodb compare the &quot;_id&quot; field when doing query like the following:

    db.data.find({&quot;_id&quot;:{$gt:ObjectId(&quot;502aa46c0674d23e3cee6152&quot;)}}).sort({&quot;_id&quot;:1}).limit(10);

Is it purely based on timestamp portion of the id?


mongodb sort order on _id

Am running MongoDB 2.2 on Ubuntu and if I run:

    sudo mongod

I get an error that it can&#39;t find /data/db, which is not where the database is. In mongod.conf the database path is specified as the Ubuntu 10gen default `/var/lib/mongodb` which is where the db is located. Seems like `mongod` is not finding the conf file. So when I run:

    sudo mongod -f /etc/mongodb.conf

The server starts up fine and output is logged to the log file: `/var/log/mongodb/mongodb.log`. All is happy. I can switch to another shell, log into mongo shell, see the databases and run queries.

So, I cancel out of that and try to run as a service:

    &gt; sudo status mongodb
    mongodb stop/waiting
    &gt; sudo start mongodb
    mongodb start/running, process 10468

Looks good so far, but the mongo server did not start. Running another:

    &gt; sudo status mongodb
    mongodb stop/waiting
    &gt; mongo
    MongoDB shell version: 2.2.0
    connecting to: test
    Sat Sep  1 19:07:43 Error: couldn&#39;t connect to server 127.0.0.1:27017 src/mongo/shell/mongo.js:91
    exception: connect failed

&quot;test&quot; is not the correct database, and nothing appears in the log file.

I am at a loss as to what could be wrong. I checked the upstart scripts and they seem fine. `/etc/init/mongodb.conf` runs:

    mongodb --exec  /usr/bin/mongod -- --config /etc/mongodb.conf

MongoDB on Ubuntu won&#39;t start as a service, nothing in the log

It seems mongo does not allow insertion of keys with a dot (.) or dollar sign ($) however when I imported a JSON file that contained a dot in it using the mongoimport tool it worked fine. The driver is complaining about trying to insert that element.

This is what the document looks like in the database:

    {
        &quot;_id&quot;: {
            &quot;$oid&quot;: &quot;...&quot;
        },
        &quot;make&quot;: &quot;saab&quot;,
        &quot;models&quot;: {
            &quot;9.7x&quot;: [
                2007,
                2008,
                2009,
                2010
            ]
        }
    }

Am I doing this all wrong and should not be using hash maps like that with external data (i.e. the models) or can I escape the dot somehow? Maybe I am thinking too much Javascript-like.

MongoDB dot (.) in key name

It seems to me that when you are creating a Mongo document and have a field `{key: value}` which is sometimes not going to have a value, you have two options:

 1. Write `{key: null}` i.e. write null value in the field
 2. Don&#39;t store the key in that document at all

Both options are easily queryable, in one you query for `{key : null}` and the other you query for `{key : {$exists : false}}`.

I can&#39;t really think of any differences between the two options that would have any impact in an application scenario (except that option 2 has slightly less storage).

Can anyone tell me if there are any reasons one would prefer either of the two approaches over the other, and why?

**EDIT**

After asking the question it also occurred to me that indexes may behave differently in the two cases i.e. a sparse index can be created for option 2.

Storing null vs not storing the key at all in MongoDB

## Basic problem

I have a bunch of records and I need to get latest (most recent) and the oldest (least recent).

When googling I found [this topic](https://groups.google.com/forum/?fromgroups=#!searchin/mongoose-orm/oldest/mongoose-orm/z93TqQ2lHJ0/PdBpnZ-HPVEJ) where I saw a couple of queries:

    // option 1
    Tweet.findOne({}, [], { $orderby : { &#39;created_at&#39; : -1 } }, function(err, post) {
      console.log( post );
    });
    // option 2
    Tweet.find({}, [], {sort:[[&#39;arrival&#39;,-1]]}, function(err, post) {
      console.log( post );
    });

Unfortunatly they both error:

    TypeError: Invalid select() argument. Must be a string or object.

The link also has this one:

    Tweet.find().sort(&#39;_id&#39;,&#39;descending&#39;).limit(15).find(function(err, post) {
      console.log( post );
    });

and that one errors:

    TypeError: Invalid sort() argument. Must be a string or object.

So how can I get those records?

## Timespan

Even more ideally I just want the difference in time (seconds?) between the oldest and the newest record, but I have no clue on how to start making a query like that.

This is the schema:

    var Tweet = new Schema({
	    body: String
	  , fid: { type: String, index: { unique: true } }
	  , username: { type: String, index: true }
	  , userid: Number
	  , created_at: Date
	  , source: String
	});

I&#39;m pretty sure I have the most recent version of mongoDB and mongoose.

## EDIT

This is how I calc the timespan based on the answer provided by JohnnyHK:

    var calcDays = function( cb ) {
      var getOldest = function( cb ) {
        Tweet.findOne({}, {}, { sort: { &#39;created_at&#39; : 1 } }, function(err, post) {
          cb( null, post.created_at.getTime() );
        });
      }
        , getNewest = function( cb ) {
        Tweet.findOne({}, {}, { sort: { &#39;created_at&#39; : -1 } }, function(err, post) {
          cb( null, post.created_at.getTime() );
        });
      }

      async.parallel({ 
        oldest: getOldest
      , newest: getNewest
      }
        , function( err, results ) {
          var days = ( results.newest - results.oldest ) / 1000 / 60 / 60 / 24;
          // days = Math.round( days );
          cb( null, days );
        }
      );
    }

How to get the latest and oldest record in mongoose.js (or just the timespan between them)

I am writing a NodeJS server with ExpressJS, PassportJS, MongoDB and MongooseJS. I just managed to get PassportJS to use user data obtained via Mongoose to authenticate.

But to make it work, I had to use a &quot;findById&quot; function like below.

    var UserModel = db.model(&#39;User&#39;,UserSchema);
    
    UserModel.findById(id, function (err, user) { &lt; SOME CODE &gt; } );

`UserModel` is a Mongoose model. I declare the schema, `UserSchema` earlier. So I suppose `UserModel.findById()` is a method of the Mongoose model?

**Question**

What does `findById` do and is there documentation on it? I googled around a bit but didn&#39;t find anything.

MongoDB via Mongoose JS - What is findByID?

I&#39;m using `Mongoose` version 3 with `MongoDB` version 2.2. I&#39;ve noticed a `__v` field has started appearing in my `MongoDB` documents. Is it something to do with versioning? How is it used?

What is the &quot;__v&quot; field in Mongoose

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?

Content Type	Original Author	Original Content on Stackoverflow
Question	silverfighter	View Question on Stackoverflow
Solution 1 - node.js	JohnnyHK	View Answer on Stackoverflow
Solution 2 - node.js	martynas	View Answer on Stackoverflow

Determine if a record "is new" in the pre save callback

node.js Problem Overview

node.js Solutions

Solution 1 - node.js

Solution 2 - node.js

Insert using LEFT JOIN and INNER JOIN

TaskCompletionSource : When to use SetResult() versus TrySetResult(), etc

Attributions