extends layout

block content
  h2 Schemas
  :markdown
    If you haven't yet done so, please take a minute to read the [quickstart](./index.html) to get an idea of how Mongoose works.
  :markdown
    If you are migrating from 2.x to 3.x please take a moment to read the [migration guide](./migration.html).
  :markdown
    This page covers `Schema` [definition](#definition), [plugins](#plugins), instance [methods](#methods), [statics](#statics), [indexes](#indexes), [virtuals](#virtuals) and [options](#options). Let's start with `Schema` definition.
  h3#definition Defining your schema
  p
    | Everything in Mongoose starts with a Schema. Each schema maps to a MongoDB collection and defines the shape of the documents within that collection.
  :js
    var blogSchema = new Schema({
      title:  String,
      author: String,
      body:   String,
      comments: [{ body: String, date: Date }],
      date: { type: Date, default: Date.now },
      hidden: Boolean,
      meta: {
        votes: Number,
        favs:  Number
      }
    })
  p
    em
      | If you want to add additional keys later, use the 
      a(href="./api.html#schema_Schema-add") Schema#add
      |  method.
  p 
    | Each key in our 
    code blogSchema
    |  defines a property in our documents which will be cast to its associated 
    a(href="./api.html#schematype_SchemaType") SchemaType
    |. Keys may also be assigned nested objects containing further key/type definitions 
    em (e.g. the `meta` property above).
    |  For example, we've defined a 
    code title
    |  which will be cast to the 
    a(href="./api.html#schema-string-js") String
    |  SchemaType and 
    code date
    |  which will be cast to a 
    code Date
    |  SchemaType.
  p
    | The permitted SchemaTypes are 
    ul
      li String
      li Number
      li Date
      li Buffer
      li Boolean
      li Mixed
      li ObjectId
      li Array
    | Read more about them 
    a(href="./schematypes.html") here
    | .
  p
    | Schemas not only define the structure of your document and casting of properties, they also define document 
    a(href="#methods") instance methods
    |, static 
    a(href="#statics") Model methods
    |, 
    a(href="#indexes") compound indexes
    |  and document lifecycle hooks called 
    a(href="./middleware.html") middleware
    |.
  h3#plugins Pluggable
  p
    | Schemas are 
    a(href="./plugins.html") pluggable
    |  which allows us to package up reusable features into 
    a(href="http://plugins.mongoosejs.com") plugins
    |  that can be shared with the community or just between your projects.
  h3#methods Instance methods
  p 
    a(href="./models.html") Models
    |  are just fancy 
    code constructor
    |  functions. As such they can have prototype methods inherited by their instances. In the case of Mongoose, instances are 
    a(href="./documents.html") documents
    |.
  p
    | Defining an instance method is easy.
  :js
    var animalSchema = new Schema({ name: String, type: String });

    animalSchema.methods.findSimilarTypes = function (cb) {
      return this.model('Animal').find({ type: this.type }, cb);
    }
  p
    | Now all of our 
    code animal
    |  instances have a 
    code findSimilarTypes
    |  method available to it.
  :js
    var Animal = mongoose.model('Animal', animalSchema);
    var dog = new Animal({ type: 'dog' })

    dog.findSimilarTypes(function (err, dogs) {
      console.log(dogs) // woof
    })
  h3#statics Statics
  p 
    | Adding static constructor methods to Models is simple as well. Continuing with our 
    code animalSchema
    |:
  :js
    animalSchema.statics.findByName = function (name, cb) {
      this.find({ name: new RegExp(name, 'i'), cb);
    }

    var Animal = mongoose.model('Animal', animalSchema);
    Animal.findByName('fido', function (err, animals) {
      console.log(animals);
    })
  h3#indexes Indexes
  p
    a(href="http://www.mongodb.org/display/DOCS/Indexes") Indexes
    |  can be defined 
    a(href="./api.html#schematype_SchemaType-index") at
    | 
    a(href="./api.html#schematype_SchemaType-unique") the
    | 
    a(href="./api.html#schematype_SchemaType-sparse") path
    | 
    a(href="./api.html#schematype_SchemaType-expires") level
    |  or the 
    code schema
    |  level. Defining indexes at the schema level is necessary when defining 
    a(href="http://www.mongodb.org/display/DOCS/Indexes#Indexes-CompoundKeys", target="_blank") compound indexes
    |.
  :js
    animalSchema.index({ name: 1, type: -1 });
  p
    | When your application starts up, Mongoose automatically calls 
    code ensureIndex
    |  for each defined index. This behavior can be disabled by setting the 
    code autoIndex
    |  option of your schema to false.
  :js
    animalSchema.set('autoIndex', false)
    // or
    new Schema({..}, { autoIndex: false })
  p
    | See also the 
    a(href="./api.html#model_Model-ensureIndexes")
      code Model#ensureIndexes
    |  method.

  h3#virtuals Virtuals
  :markdown
    [Virtual](./api.html#schema_Schema-virtual) attributes are attributes that are convenient to have around but that do not get persisted to MongoDB.
  :js
    var personSchema = new Schema({
      name: {
        first: String,
        last: String
      }
    });

    var Person = mongoose.model('Person', personSchema);

    var bad = new Person({
        name: { first: 'Walter', last: 'White' }
    });
  :markdown
    Suppose we want to log the full name of `bad`. We could do this manually like so:
  :js
    console.log(bad.name.first + ' ' + bad.name.last); // Walter White
  :markdown
    Or we could add a `virtual` attribute [getter](./api.html#virtualtype_VirtualType-get) to our `personSchema` so we don't need to write out this string concatenation mess each time:
  :js
    personSchema.virtual('name.full').get(function () {
      return this.name.first + ' ' + this.name.last;
    })
  :markdown
    Now, when we access our virtual full name property, our getter function will be invoked and the value returned:
  :js
    console.log('%s is insane', bad.name.full) // Walter White is insane
  :markdown
    It would also be nice to be able to set `this.name.first` and `this.name.last` by setting `this.name.full`. For example, if we wanted to change `bad`'s `name.first` and `name.last` to 'Breaking' and 'Bad' respectively, it'd be nice to just:
  :js
    bad.name.full = 'Breaking Bad';
  :markdown
    Mongoose let's you do this as well through its virtual attribute [setters](./api.html#virtualtype_VirtualType-set):
  :js
    personSchema.virtual('name.full').set(function (name) {
      var split = name.split(' ');
      this.name.first = split[0];
      this.name.last = split[1];
    })

    ...

    mad.name.full = 'Breaking Bad';
    console.log(mad.name.first) // Breaking
  :markdown
    If you need attributes that you can get and set but that are not themselves persisted to MongoDB, virtual attributes is the Mongoose feature for you.

  h3#options Options
  :markdown
    `Schema`s have a few configurable options which can be passed to the constructor or `set` directly:
  :js
    new Schema({..}, options);

    // or

    var schema = new Schema({..});
    schema.set(option, value);

  :markdown
    Valid options:

    - [safe](#safe)
    - [strict](#strict)
    - [capped](#capped)
    - [versionKey](#versionKey)
    - [autoIndex](#autoIndex)

  h4#safe option: safe
  :markdown
    This option is passed to MongoDB with all operations and let's us specify if errors should be returned to our callbacks as well as tune write behavior.

  :js
    var safe = true;
    new Schema({ .. }, { safe: safe })

  :markdown
    By default this is set to `true` for all schemas which guarentees that any occurring error gets passed back to our callback.
    By setting `safe` to something else like `{ j: 1, w: 2, wtimeout: 10000 }` we can guarantee the write was committed to the MongoDB journal (j: 1), at least 2 replicas (w: 2), and that the write will timeout if it takes longer than 10 seconds (wtimeout: 10000). Errors will still be passed to our callback.

    There are other write concerns like `{ w: "majority" }` too. See the MongoDB [docs](http://www.mongodb.org/display/DOCS/getLastError+Command) for more details.

  :js
    var safe = { w: "majority", wtimeout: 10000 };
    new Schema({ .. }, { safe: safe })

  h4#strict option: strict
  :markdown
    The strict option, (enabled by default), ensures that values added to our model instance that were not specified in our schema do not get saved to the db.
    _NOTE: do not set to false unless you have good reason._

  :js
    var thingSchema = new Schema({..})
    var Thing = db.model('Thing', schemaSchema);
    var thing = new Thing({ iAmNotInTheSchema: true });
    thing.save() // iAmNotInTheSchema is not saved to the db

    // set to false..
    var thingSchema = new Schema({..}, { strict: false });
    var thing = new Thing({ iAmNotInTheSchema: true });
    thing.save() // iAmNotInTheSchema is now saved to the db!!

  :markdown
    This value can be overridden at the model instance level by passing a second boolean argument:

  :js
    var Thing = db.model('Thing');
    var thing = new Thing(doc, true);  // enables strict mode
    var thing = new Thing(doc, false); // disables strict mode

  :markdown
    The `strict` option may also be set to `"throw"` which will cause errors to be produced instead of ignoring the bad data.

  :markdown
    _NOTE: in mongoose v2 the default was false._

  h4#shardkey option: shardKey
  :markdown
    The `shardKey` option is used when we have a [sharded MongoDB architecture](http://www.mongodb.org/display/DOCS/Sharding+Introduction). Each sharded collection is given a shard key which must be present in all insert/update operations. We just need to set this schema option to the same shard key and we’ll be all set.

  :js
    new Schema({ .. }, { shardkey: { tag: 1, name: 1 }})

  :markdown
    _Note that Mongoose does not send the `shardcollection` command for you. You must configure your shards yourself._

  h4#capped option: capped
  :markdown
    Mongoose supports MongoDBs [capped](http://www.mongodb.org/display/DOCS/Capped+Collections) collections. To specify the underlying MongoDB collection be `capped`, set the `capped` option to the maximum size of the collection in [bytes](http://www.mongodb.org/display/DOCS/Capped+Collections#CappedCollections-size.).
  :js
    new Schema({..}, { capped: 1024 })
  :markdown
    The `capped` option may also be set to an object if you want to pass additional options like [max](http://www.mongodb.org/display/DOCS/Capped+Collections#CappedCollections-max) or [autoIndexId](http://www.mongodb.org/display/DOCS/Capped+Collections#CappedCollections-autoIndexId). In this case you must explicitly pass the `size` option which is required.
  :js
    new Schema({..}, { capped: { size: 1024, max: 1000, autoIndexId: true })

  h4#versionKey option: versionKey
  :markdown
    The `versionKey` is a property set on each document when first created by Mongoose. This keys value contains the internal [revision](http://aaronheckmann.posterous.com/mongoose-v3-part-1-versioning) of the document. The name of this document property is configurable. The default is `__v`. If this conflicts with your application you can configure as such:
  :js
    var schema = new Schema({ name: 'string' });
    var Thing = db.model('Thing', schema);
    var thing = new Thing({ name: 'mongoose v3' });
    thing.save(); // { __v: 0, name: 'mongoose v3' }

    // customized versionKey
    new Schema({..}, { versionKey: '_somethingElse' })
    var Thing = db.model('Thing', schema);
    var thing = new Thing({ name: 'mongoose v3' });
    thing.save(); // { _somethingElse: 0, name: 'mongoose v3' }

  :markdown
    Document versioning can also be disabled by setting the `versionKey` to false. _DO NOT disable versioning unless you [know what you are doing](http://aaronheckmann.posterous.com/mongoose-v3-part-1-versioning)._
  :js
    new Schema({..}, { versionKey: false })
    var Thing = db.model('Thing', schema);
    var thing = new Thing({ name: 'no versioning please' });
    thing.save(); // { name: 'no versioning please' }
  h4#autoIndex option: autoIndex
  :markdown
    At application startup, Mongoose sends an `ensureIndex` command for each index declared in your `Schema`. As of Mongoose v3, indexes are created in the `background` by default. If you wish to disable the auto-creation feature and manually handle when indexes are created, set your `Schema`s `autoIndex` option to `false` and use the [ensureIndexes](./api.html#model_Model-ensureIndexes) method on your model.
  :js
    var schema = new Schema({..}, { autoIndex: false })
    var Clock = db.model('Clock', schema);
    Clock.ensureIndexes(callback);

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