title: Mongoose data saving without _id
body: <p>I am using mongoose with node.js application. I don't want _id field in record.
  I am using this code to save my record without _id field. But it is giving error</p>
  
  <blockquote>
    <p>document must have an _id before saving</p>
  </blockquote>
  
  <pre><code>var mongoose = require('mongoose');
  var Schema = mongoose.Schema;
  
  var PlayerSchema = new Schema({
      player_id :  { type: Number },
      player_name : { type: String },
      player_age  : { type: Number },
      player_country : { type: String }
  }
  , { _id: false }
  );
  
  var Player =  mongoose.model('Player', PlayerSchema );
  
          var athlete = new Player();
          athlete.player_id = 1;
          athlete.player_name = "Vicks";
          athlete.player_age  = 20;
          athlete.player_country = "UK";
  
          athlete.save(function(err) {
              if (err){
                  console.log("Error saving in PlayerSchema"+ err);
              }
          });
  </code></pre>
  
  <p>I am using mongoose version 3.8.14</p>