Overview

For instructions on upgrading to newer versions, visit mongoid.org.

As of version 5.0.2, please refer to the github releases for change logs.

5.0.1

Resolved Issues

MONGOID-3020 Test added to show it's no longer an issue.
MONGOID-3025 Test added to show it's no longer an issue.
MONGOID-3061 No longer an issue.
MONGOID-3073 Test added to show it's no longer an issue.
MONGOID-3085 Test added to show it's no longer an issue.
MONGOID-3101 No longer an issue.
MONGOID-3160 No longer an issue.
MONGOID-3176 No longer an issue.
MONGOID-3214 Test added to show it's no longer an issue.
MONGOID-3296 Add update callback for counter_cache.
MONGOID-3326 Test added to show it's no longer an issue.
MONGOID-3361 No longer an issue.
MONGOID-3365 Test added to show it's no longer an issue.
MONGOID-3402 Apply persistence options to parent.
MONGOID-3524 No longer an issue.
MONGOID-3529 Test exists already showing it's not an issue.
MONGOID-3543 Test exists already showing it's not an issue.
MONGOID-3611 Test added to show it's no longer an issue.
MONGOID-3650 No longer an issue.
MONGOID-3826](https://jira.mongodb.org/browse/MONGOID-3826), [MONGOID-4109 Fix Timelessness leaks.
MONGOID-3946 Test added to show it's no longer an issue.
MONGOID-3969 Test added to show it's no longer an issue.
MONGOID-3971 Not an issue.
MONGOID-3979 Not an issue, tests exist already.
MONGOID-3985 Not an issue.
MONGOID-4078 Behavior is intended.
MONGOID-4079 Not an issue.
MONGOID-4088 Account for sub-document dot notation with #pluck results.
MONGOID-4098 Fixed by a change to the Ruby driver. See RUBY-1029.
MONGOID-4101 Not an issue.
MONGOID-4106 Not an issue.
MONGOID-4110 Not an issue.
MONGOID-4119 Ensure that criteria selector becomes pipeline operator value.
MONGOID-4121 Not an issue.
MONGOID-4123 Fixed as a result of MONGOID-4159.
MONGOID-4125 Make sure none scopes referenced in procs are applied.
MONGOID-4132 Not an issue.
MONGOID-4157 Fixed by version 2.1.2 of the Ruby driver.
MONGOID-4162 Adapt index option mappings to new driver. (@Nielsomat)
MONGOID-3737 Test added to show it's no longer an issue.
MONGOID-3621 Not an issue.
MONGOID-3551 Not an issue.
MONGOID-3696 Test added to show it's no longer an issue.
MONGOID-3858 Test added to show it's no longer an issue.
MONGOID-3672 Not an issue.
MONGOID-4172 Use positional operator only on 1 level deep nesting.
Added public cert to repo and sign gem if private key is present

5.0.0

Major Changes (Backwards Incompatible)

Mongoid now uses the official Mongo Ruby Driver 2.x instead of Moped.
Most driver specific configuration options have changed, please see here for the new options.
All references to session are now replaced with client. This includes the mongoid.yml configuration, store_in options, and all exceptions and modules with Session in the name.
find_and_modify has been removed and replaced with 3 options: find_one_and_update, find_one_and_delete and find_one_and_replace.
text_search has been removed as it is now a $text option in a query from 2.6 on.
Mongoid no longer supports MongoDB 2.2 - support is now for only 2.4 and higher.
#3768 first and last no longer add an _id sort when no sorting options have been provided. In order to guarantee that a document is the first or last, it needs to now contain an explicit sort.
Document#deleted? alias has been removed, please continue to use Document#destroyed?.

New Features

#4016 Allow private and protected setters on fields for atomic operations. (Rob Smith)
#3985 Return nil when using {upsert: true} in find_and_modify (Adrien Siami)
#3963 Allow extended JSON object ids to be passed to find.
#3846 Allow #pluck when none is used in criteria. (Braulio Martinez)

Resolved Issues

#4091 Use subclass context when calling a scope defined in a superclass. (Edgars Beigarts)
#4075 Made remove index logging specific to each index that was actually getting removed.
#4071 Fixed loading of enumerable relation to check the added documents when iterating.
#4077 Many relations now include Enumerable.
#4052 Fixed uniqueness validation on localized fields with no value.
#4033 Removed all uses of the $ positional operator in atomic updates.
#4030 Dup/clone exceptions auto-include dynamic attributes.
#4005 Fixed inclusion of mongoid with Rails components that don't have the Rails environment.
#3993 Fixes issue where dup/clone fails for embedded documents that use store_as without using ::Mongoid::Attributes::Dynamic
#3991 Fixed embedded documents not flagging as changed after calling #changed? and modifying the child elements.
#3874 Adding snapshot option to context.
#3868 Loading models in rake tasks now expands the rails path.
#3764 Fixed case statement check for enumerable targets.
#3740 Fixes Missing attribute: '_id' error when using methods only or without (dx7)
#3631 Fixes issue where before_save callback can get called twice after a child create
#3599 Fixed application of default scopes from superclass in subclasses.
#3104 Fixed enumerable targets to check first/last in proper order.

4.0.2

New Features

#3931 Add #find_or_create_by! method to many associations. (Tom Beynon)
#3731 Add find_by! method. (Guillermo Iguaran)

Resolved Issues

#3722 Use the right database name when combining #store_in and #with. (Arthur Neves)
#3934 Dont apply sort when doing a find_by. (Arthur Neves)
#3935 fix multiple fields sorting on contextual memory. (chamnap)
#3904 BSON::Document#symbolize_keys should return keys as symbols. (Arthur Neves)
#3948 Fix remove_undefined_indexes on rails 4.2, to symbolize right the Document keys. (Adam Wróbel)
#3626 Document#to_key, needs to return a ObjectId as String so we can query back using that id. (Arthur Neves)
#3888 raise UnknownAttributeError when 'set' is called on non existing field and ::Mongoid::Attributes::Dynamic is not included in model. (Shweta Kale)
#3889 'set' will allow to set value of non existing field when ::Mongoid::Attributes::Dynamic is included in model. (Shweta Kale)
#3812 Fixed validation context when saving (Yaroslav Zemlyanuhin)

4.0.1

Resolved Issues

#3911 Fix relations named "parent". (nkriege)
#3792/\#3881 Fix many internal calls to #_id instead of #id to avoid issues when overloading #id (Gauthier Delacroix)
#3847 Fix 'QueryCache#get_more' result, when collection has more documents than first query batch. (Angelica Korsun)
#3684 Dont raise MissingAttributeError, when using a only() scope. (Arthur Neves)
#3703 pluck method should not compact the values. (Arthur Neves)
#3773 Use nanoseconds for cache_key timestamp instead of plain seconds. (Máximo Mussini)

4.0.0

Major Changes (Backwards Incompatible)

#3320 Remove Rails dependencies on database rake tasks. (Arthur Neves)

All db:* rake tasks should work as before when using Rails.
When not in a Rails, just load the database tasks using:

  load 'mongoid/tasks/database.rake'

Mongoid 4 now only supports MongoDB 2.4.0 and higher.
Document#metadata has been renamed to Document#relation_metadata to avoid common conflicts. Relation proxies also have this renamed to the same as well.
Scopes and default scopes must now all be defined within lambdas or procs.
skip_version_check config option was removed.
IdentityMap removed. (Arthur Neves)
Eager load rework. Eager load now doesnt need the identity map to load related documents. A set of preloaders can eager load the associations passed to .includes method. (Arthur Neves)

Mongoid now supports the new read preferences that the core drivers provide. These include:

- `:primary`: Will always read from a primary node. (default)
- `:primary_preferred`: Attempt a primary first, then secondary if none available.
- `:secondary`: Will always read from a secondary node.
- `:secondary_preferred`: Attempt a secondary first, then primary if none available.
- `:nearest`: Attempt to read from the node with the lowest latency.

Sample syntax:

  Person.with(read: :secondary).first

The `:consistency` option is no longer valid, use the `:read` option now.

Mongoid now defaults all writes to propagate (formerly "safe mode") and now has different propagate semantics:

- `{ w: -1 }`: Don't verify writes and raise no network errors.
- `{ w: 0 }`: Don't verify writes and raise network errors.
- `{ w: 1 }`: Verify writes on the primary node. (default)
- `{ w: n }`: Verify writes on n number of nodes.
- `{ w: "majority" }`: Verify writes on a majority of nodes.

Sample syntax:

  Person.with(write: {w: :majority}).create!(name: "John")

The `:safe` option is no longer valid use the `:write` option now.

#3230 Array and Hash fields now validate that the correct types are getting set, instead of allowing any value. (Rodrigo Saito)
#3043/\#2949 Rework on the internals of persistence options. (Arthur Neves)
Mongoid now requires Active Model 4 or higher.
Document#set now accepts multiple attributes in the form of a hash, instead of the previous (field, value) args. Field aliases and typecasting are also now supported in this operation.
```
document.set(name: "Photek", likes: 10000)
```
Document#rename now accepts multiple attributes in the form of a hash, instead of the previous (field, value) args. Field aliases are supported.
```
document.rename(first_name: "fn", last_name: "ln")
```
Document#inc now accepts multiple attributes in the form of a hash, instead of previously only being able to increment one value at a time. Aliases and serialization is supported.
```
document.inc(score: 10, place: -1, lives: -10)
```
Document#pop now accepts multiple attributes in the form of a hash, instead of previously only being able to pop one value at a time. Aliases and serialization is supported.
```
document.pop(names: 1, aliases: -1)
```
Document#bit now accepts multiple attributes in the form of a hash, instead of previously only being able to apply one set of operations at a time. Aliases and serialization are supported.
```
document.bit(age: { and: 13 }, score: { or: 13 })
```
Document#pull now accepts multiple attributes in the form of a hash, instead of previously only being able to pull one value at a time. Aliases and serialization is supported.
```
document.pull(names: "James", aliases: "007")
```
Document#pull_all now accepts multiple attributes in the form of a hash, instead of previously only being able to pull one value at a time. Aliases and serialization is supported.
```
document.pull_all(names: ["James", "Bond"], aliases: ["007"])
```
Document#push_all has been removed since it was deprecated in MongoDB 2.4. Use Document.push instead.
Document#push now accepts multiple attributes in the form of a hash, and can handle the pushing of single values or multiple values to the field via $push with $each. Aliases and serialization is supported.
```
document.push(names: "James", aliases: [ "007", "Jim" ])
```
Document#add_to_set now accepts multiple attributes in the form of a hash, and now aliases and serialization are supported.
```
document.add_to_set(names: "James", aliases: "007")
```
Criteria atomic operations API is now changed to match the changes in the single document atomic API, for example:
```
Band.where(name: "Depeche Mode").inc(likes: 10, followers: 20)
```

#3399 #create and #create! on relations can now take an array of attributes as the first parameter to create multiple documents at once.

person.addresses.create([{ street: "Bond" }, { street: "Upper" }])
person.addresses.create!([{ street: "Bond" }, { street: "Upper" }])

#3141 rake db:test:prepare now sets up all defined indexes if Mongoid is the only ODM/ORM in the environment.
#3138 update_attributes can now be accessed simply by calling update.
#3083 A new rake task: rake db:mongoid:remove_undefined_indexes has been added to remove indexes from the database that are not explicitly defined in the models. (Aidan Feldman)

#3029 The relation_field field that is added for a single use case with polymorphic relations has been removed. So where the following would work before:

  class Eye
    include Mongoid::Document
    belongs_to :eyeable, polymorphic: true
  end

  class Face
    include Mongoid::Document
    has_one :left_eye, class_name: "Eye", as: :eyeable
    has_one :right_eye, class_name: "Eye", as: :eyeable
  end

This would now need to be modeled as (with the appropriate migration):

  class Eye
    include Mongoid::Document
    belongs_to :left_socket, class_name: "Face", inverse_of: :left_eye
    belongs_to :right_socket, class_name: "Face", inverse_of: :right_eye
  end

  class Face
    include Mongoid::Document
    has_one :left_eye, class_name: "Eye", inverse_of: :left_socket
    has_one :right_eye, class_name: "Eye", inverse_of: :right_socket
  end

#3075 update_attribute now properly calls the setter method instead of using write_attribute.
#3060 Allow atomically blocks to allow multiple calls of the same type. (Brian Norton)
#3037 Model indexes are no longer stored in an index_options hash on the model class. Instead, an array named index_specifications now exists on the class which contains a list of Indexable::Specification objects. This is so we could properly handle the case of indexes with the same keys but different order.
#2956 Caching on queries now only happens when cache is specifically called. (Arthur Neves)
#2659 Mongoid::Railtie now properly uses only one initializer and the name has changed to mongoid.load-config.
#2656 rake db:reseed is now rake db:reset (Arthur Neves)
#2648 Boolean becomes ::Mongoid::Boolean to avoid polluting the global namespace with a commonly used class by other libraries.
#2603 Return values from setters are now always the set value, regardless of calling the setter or using send.
#2597 Mongoid::Observer was removed in line with Rails 4.
#2563 The allow_dynamic_fields configuration option has been removed as dynamic fields are now allowed on a per-model level. In order to allow a model to use dynamic fields, simply include the module in each. (Josh Martin)
```
class Band
  include Mongoid::Document
  include Mongoid::Attributes::Dynamic
end
```
#2497 Calling to_json no longer tampers with the return value from the driver, and proper returns { "$oid" : object_id.to_s } instead of just the string representation previously.
#2433 Mongoid::Paranoia has been removed.
#2432 Mongoid::Versioning has been removed.
#2218 Creating or instantiating documents that have default scopes will now apply the default scope to the document, if the scope is not complex.
#2200 Mass assignment security now mirrors Rails 4's behavior. without_protection option was also removed. attr_accessible class method was removed. Mongoid and Strong parameters should work fine for mass assignment protection.
delete_all and destroy_all no longer take a :conditions hash but just the raw attributes.
#1908 Documents now loaded from criteria using #only or #without will now raise an error when attempting to save, update, or delete these records. Additionally fields excluded from the fields retrieved from the database will also raise an exception when trying to access them.

#1344 Atomic updates can now be executed in an atomically block, which will delay any atomic updates on the document the block was called on until the block is complete.

Update calls can be executed as normal in the block:

  document.atomically do
    document.inc(likes: 10)
    document.bit(members: { and: 10 })
    document.set(name: "Photek")
  end

The document is also yielded to the block:

  document.atomically do |doc|
    doc.inc(likes: 10)
    doc.bit(members: { and: 10 })
    doc.set(name: "Photek")
  end

The atomic commands are have a fluid interface:

  document.atomically do |doc|
    doc.inc(likes: 10).bit(members: { and: 10 }).set(name: "Photek")
  end

If the fluid interface is leveraged without the `atomically` block, the
operations will persist in individual calls. For example, the following
would hit the database 3 times without the block provided:

  doc.inc(likes: 10).bit(members: { and: 10 }).set(name: "Photek")

The block is only good for 1 document at a time, so embedded and root
document updates cannot be mixed at this time.

New Features

Mongoid now uses ActiveSupport::LogSubscriber to subscribe logs, and ActiveSupport::Notifications to send operation logs. (Arthur Neves) Example of log subscription:
```
ActiveSupport::Notifications.subscribe('query.moped') do |event|
..
end
```
Field types can now use symbols as well as class names. See: https://github.com/mongoid/mongoid/blob/master/lib/mongoid/fields.rb#L16 for the available mappings.
#3580 Fields can now be reset to their default values, with the methods:
```
document.reset_name_to_default!
```
#3513 Documents now have a #destroy! method that will raise a Mongoid::Errors::DocumentNotDestroyed error if a destroy callback returns a false value.
#3496 Added class level and criteria level find_or_create_by!.
#3479 Map/reduce now respects criteria no timeout options if output is not inline.
#3478 Criteria objects now have a #none method that will cause the criteria to never hit the database and always have zero documents.
```
Band.none
Band.none.where(name: "Tool") # Always has zero documents.
```
#3410 Mongoid now has a query cache that can be used as a middleware in Rack applications. (Arthur Neves)
```
For Rails:

config.middleware.use(Mongoid::QueryCache::Middleware)
```
#3319 Counters can now be reset from a document instance:
```
document.reset_counters(:relation)
```
#3310 embedded_in relations now accept a touch option to update parents.
#3302 Aliasing using alias_attribute now properly handles aliases in criteria.
#3155 Range field will persist the exclude_end when provided. (Daniel Libanori)
#3146 Adding :overwrite field option, when it`s true, it wont check duplicates. (Daniel Libanori)
#3002 Reloading the Rails console will also now clear Mongoid's identity map.
#2938 A configuration option duplicate_fields_exception has been added that when set to true will raise an exception when defining a field that will override an existing method. (Arthur Neves)

#2924 MongoDB 2.4 beta text search now has a DSL provided by Mongoid. Like other queries, text searches are lazy evaluated, and available off the class or criteria level.

Note that any 3rd party gem that provides a `text_search` method will now no
longer work with Mongoid, and will need to change its syntax. Examples:

  Band.text_search("mode").project(name: 1).each do |doc|
    # ...
  end

  Band.limit(10).text_search("phase").language("latin")
  Band.where(:likes.gt => 1000).text_search("lucy")

#2855 Multiple extensions can now be supplied to relations. (Daniel Libanori)

Resolved Issues

#3676 Make pluck work with embedded associations (Arthur Neves)
#2898 Dirty attribute methods now properly handle field aliases. (Niels Ganser)
#3620 Add ActiveModel module instance methods to prohibited_methods list. (Arthur Neves)
#3610 Don't allow atomic operations on read-only attributes (Frederico Araujo)
#3619 Don't validate documents that are flagged for destruction. (Christopher J. Bottaro)
#3617 Don't skip index creation on cyclic documents. (shaiker)
#3568 Fixed missing attributes error on present localized fields.
#3514 Fixed query cache to work on first/last calls.
#3383/\#3495 Fix has_and_belongs_to_many eager load. (Arthur Neves)
#3492 $rename operations should not mongoize values. (Vladislav Melanitskiy)
#3490 Allow localized fields to work with boolean false values.
#3487 Map Boolean to ::Mongoid::Boolean in field definitions. (Arthur Neves)
#3449 Touch needs to work for create and update. (Greggory Rothmeier)
#3347 Creating documents off of scopes for embedded relations now properly sets the parent document on the created children.
#3432 Fixed mongoization of DateTime losing precision.
#3397 Fixed $ne matcher for embedded documents to match server behavior.
#3352 Allow named scopes named "open" to work through 1-n relations.
#3348 Fixing compounded indexes having the same keys with different directions. (Arthur Neves)
#2701 Fixing extra query on belongs_to binding. (Arthur Neves)
#3089 Allow demongoization of strings to floats (Daniel Libanori)
#3278 Counter cache should update the document in memory too. (Arthur Neves)
#3242 Has_many relation must use the inverse foreign_key. (Arthur Neves)
#3233 Don't double call validation callbacks when cascading children and relation validation is turned on.
#3197 Improvements in the calls to aggregates on root and embedded collections. (Wojciech Piekutowski)
#3144/\#3219 Fixing name collision on @_children ivar. (Arthur Neves)
#3088 Range field can accept a hash, which could be the attribute from the db. (Daniel Libanori)
#3116 Relations instance variables are now all prefixed with _.
#3093 Only flatten 1 level when atomically pushing arrays.
#3063 Document#becomes now properly sets base object on errors. (Adam Ross Cohen)
#3019 Atomic operations will no longer attempt to persist if the document is not persisted.
#2903 Removed unused string to_a extension.

3.1.7

Resolved Issues

#3465 Fixed ambiguous relation errors where inverse_of is set to nil.
#3414 Backport skip and limit options on aggregation. (Wojciech Piekutowski)
#3469 Fix RegexpError: failed to allocate memory: /./ on .hash_dot_syntax? (Dmitry Krasnoukhov)

3.1.6

Resolved Issues

#3337 Ensure localized fields map is cloned with inheritance.
#3262 Fixed atomic array operations on HABTM foreign key fields from turning single elements into arrays.
#3282 Fixed .timeless option to use a thread local instead of a class attribute. Also remove the timeless methods from all docs, and only add to timestamps docs. (Arthur Neves)

3.1.5

Resolved Issues

#3231 Allow evolution of proxy documents to work in criteria.
#3247 Bump dependency on tzinfo to 0.3.29.
#3203 Fixed index: true specification for polymorphic relations.
#3192 Fixed aliased fields + localized fields combinations with validation. (Johnny Shields)
#3173 Fixed issues around many to many relations with custom primary keys. (Bowen Sun)
#3159 Upserting now properly flags documents as persisted.
#3137 Allow multiple belongs_to sets in a row with ids.
#3079 Embedded docs with paranoia parents were losing the _id when reloading from db, as they didnt have the right persisted? value. (Arthur Neves)
#3081 Criteria's method_missing now checks if an array responds to the provided method before calling entries in order to not hit the database if a NoMethodError was to get raised.
#3068 Fixed spec runs on non standard MongoDB ports if MONGOID_SPEC_PORT is set.
#3047 Ensure blank? and empty? don't fall through method missing on criteria.
Include updated_at on cache_key even when is a short timestamp (Arthur Neves)

3.1.4

Resolved Issues

#3044 Ensure enumerable targets match arrays in case statements.
#3034 first_or_create on criterion now properly passes the block to create instead of calling after the document was created.
#3021 Removed mongoid.yml warning from initializer, this is now handled by the session configuration options.
#3018 Uniqueness validator now properly serializes values in its check. (Jerry Clinesmith)
#3011 Fixed aliased field support for uniqueness validation. (Johnny Shields)
#3008 Fixed subclasses not being able to inherit scopes properly when scope is added post class load. (Mike Dillon)
#2991 Document.timeless now properly scopes to the instance and not thread.
#2980 Dynamic fields now properly handle in place editing of hashes and arrays. (Matthew Widmann)
#2979 pluck no longer modifies the context in place. (Brian Goff)
#2970 Fixed counter cache to properly use the name of the relation if available then the inverse class name second if not.
#2959 Nested attributes will now respect autosave: false if defined on the relation.
#2944 Fixed uniqueness validation for localized fields when case insensitive is true. (Vladimir Zhukov)

3.1.3

Resolved Issues

Dont duplicate embedded documents when saving after calling becomes method. (Arthur Neves)
#2961 Reloading a mongoid.yml configuration now properly clears previously configured sessions.
#2937 Counts can now take a true argument to factor in skip and limit. (Arthur Neves)
#2921 Don't use type in identity map selection if inheritance is not in play. (Arthur Neves)
#2893 Removed memoization of collection name and database name so lambdas with store_in work properly when changing.
#2911 The _destroy attribute on 1-n relations when processing nested attributes can now be a string or symbol when passed an array.
#2886 Fixed namespacing issue with Rails generators.
#2885 Fixed touch for aliased fields. (Niels Ganser)
#2883 Allow cyclic relations to not raise mixed relation errors.
#2867 pluck now properly handles aliased fields.
#2862 Autosaving no longer performs extra unnecessary queries. (Arthur Neves)

3.1.2

Resolved Issues

#2851 Fixed BigDecimal demongoization of NaN values. (nkem)
#2848 Fixed touch to work when usinng short timestamps. (Arthur Neves)
#2840 Fixed end-to-end no_timeout option handling.
#2826 Dynamic fields are now properly mongoized.
#2822 Marshal load of relations now properly reapplies extensions.

3.1.1

Resolved Issues

#2839 Validations fixed to use the type cast value with the exception of the numericality validator. (Lailson Bandeira)
#2838 store_in options now properly merge instead of override. (Colin MacKenzie)

3.1.0

New Features

The minimum MongoDB requirement is now raised to 2.2, since we now depend on the aggregation framework.
The minimum Active Model and Active Support dependencies have been raised to 3.2.

#2809 Relations can now specify a primary key to use instead of the id on foreign keys.

class Person
  include Mongoid::Document
  field :username, type: String
  has_many :cats, primary_key: "username"
end

class Cat
  include Mongoid::Document
  belongs_to :person, primary_key: "username"
end

#2804 $geoNear support has now been added to criteria.

Bar.where(:likes.gt => 1000).geo_near([ 52, 13 ])
Bar.geo_near([ 52, 13 ]).max_distance(0.5).spherical

#2799 Criteria#map can now accept a symbol of a field name as well as a block to perform a more optimized map. (Gosha Arinich)
```
Band.where(:likes.gt => 1000).map(:name)
```
#2798 Aggregations (sum, min, max, avg) now use the aggregation framework instead of map/reduce. (Gosha Arinich)
#2776 MongoDB 2.4.x new index types are now supported: "2dsphere", "text", and "hashed". (Irakli Janiashvili)
#2767 $maxScan support from Origin is now supported. (Jonathan Hyman)
#2701 Cleanup up extra excessive database queries with 1-1 relations.
#2693 Custom collection names can be passed to the model generator. (Subhash Bhushan)
```
rails g model band --collection=artists
```
#2688 Model.create and Model.create! now can take an array of attributes hashes to create multiple documents at once. If an array of attributes is provided then an array of documents is returned.
```
Band.create([{ name: "Tool" }, { name: "Placebo" }])
Band.create!([{ name: "Tool" }, { name: "Placebo" }])
```

#2670 Unsetting fields now accepts multiple fields instead of only 1. (Arthur Neves)

band.unset(:name, :founded)
Band.where(name: "Placebo").unset(:members, :origin)

#2669 Passing a block to Criteria#new now properly sends the block through to the model's constructor. (Arthur Neves)
#2667 exists? no longer hits the database in cases where we have the necessary information in memory.

#2665 Mongoid now supports a counter cache for belongs_to relations. (Arthur Neves)

class Band
  include Mongoid::Document
  belongs_to :label, counter_cache: "b_count"
end

class Album
  include Mongoid::Document
  belongs_to :band, counter_cache: true
end

#2662 Embedded documents that have belongs_to relations may now eager load them.
#2657 Logger getter and setter convenience methods have been added to the Config module. (Arthur Neves)
#2615 Index options can now take a specific database name if the indexes are only to exist in a database other than the default.
```
class Band
  include Mongoid::Document
  index name: 1, { database: "another_db" }
end
```

#2613 Procs can now be provided as values to store_in:

class Band
  include Mongoid::Document
  store_in database: ->{ Thread.current[:database] }
end

#2609 Pass through batch_size option to query. (Martin Mauch)
#2555 Passing hashes to find when the documents id is of type hash now properly works. (Szymon Kurcab)
#2545 The $ positional operator is used for update selectors on embedded documents that are nested 1 level deep, when appropriate.
#2539 Mongoid.models now tracks all models in the application for more accurate determination of models for things such as indexing rake tasks. (Ara Howard)

#2525 Added the ability to have short timestamped fields with aliases. This sets timestamp fields as c_at and u_at that are also aliased as created_at and updated_at for convenience. (Rodrigo Saito)

class Band
  include Mongoid::Document
  include Mongoid::Timestamps::Short # For c_at and u_at.
end

class Band
  include Mongoid::Document
  include Mongoid::Timestamps::Created::Short # For c_at only.
end

class Band
  include Mongoid::Document
  include Mongoid::Timestamps::Updated::Short # For u_at only.
end

#2465 Documents now have an attribute_before_type_cast for proper handling of validations. (Gerad Suyderhoud)
#2443 expire_after_seconds is now a valid index option (https://www.mongodb.com/docs/manual/core/indexes/#ttl-indexes, https://www.mongodb.com/docs/manual/tutorial/expire-data/).
```
class Event
  include Mongoid::Document
  field :created_at, type: DateTime
  index({ created_at: 1 }, { expire_after_seconds: 3600 })
end
```
#2373 Relations with the touch: true option will now be automatically touched when the child document is created or destroyed.
Added Document.first_or_create! and Criteria#first_or_create!. This raises a validations error if creation fails validation.
```
Band.where(name: "Depeche Mode").first_or_create!
Band.where(name: "Tool").first_or_create!(active: true)
```
Added Document.first_or_initialize and Criteria#first_or_initialize. This is the same as first_or_create but initializes a new (unpersisted) document if none is found.
```
Band.where(name: "Depeche Mode").first_or_initialize
Band.where(name: "Tool").first_or_initialize(active: true)
```
Added Model.pluck and Criteria#pluck similar to Active Record's, which returns an array of values for the provided field. (Jason Lee)
```
Band.where(name: "Depeche Mode").pluck(:_id)
Band.where(name: "Tool").pluck(:likes)
```
#2324 Embeds many relations now properly handle delete_if.
#2317 Added Document.first_or_create and Criteria#first_or_create. This will return the first matching document or create one with additional attributes if one does not exist. (incorvia)
```
Band.where(name: "Depeche Mode").first_or_create
Band.where(name: "Tool").first_or_create(active: true)
```
#2292 Added Model.each_with_index.
#2285 Config.load_configuration is now public for those who want to instantiate settings directly from a hash.
#2275 Added rake task db:mongoid:purge that will drop all collections with the exception of the system collections in the default database.

#2257 after_find callbacks have been added for when documents are returned from the database.

class Band
  include Mongoid::Document

  after_find do |doc|
    # Some logic here.
  end
end

#2223 Allow to find documents by javascript with parameters that are protected from javascript injection via Model.for_js.
```
Band.for_js("this.name = param", param: "Tool")
Band.where(:likes.gt => 1000).for_js("this.likes < this.follows")
```
#2197 When providing session configuration with no ports, Mongoid will now default these to 27017.

#2180 1-n and n-n relations now support before/after add/remove callbacks. (Rodrigo Saito)

class Band
  include Mongoid::Document

  embeds_many :albums, after_add: :notify_labels
  has_many :followers, before_remove: ->(band, follower){ notify_unfollow(follower) }
end

#2157 Criteria#update and Criteria#update_all now serialize values according to their field type, if a field is defined.

#2022 Custom callbacks can now register themselves for use with observers by using the observable macro.

class Band
  include Mongoid::Document

  define_model_callbacks :notification
  observable :notification
end

class BandObserver < Mongoid::Observer

  def before_notification(band)
    #...
  end

  def after_notification(band)
    #...
  end
end

#1766 Many to many relations will not touch the database if the foreign key is an empty array.
#1564 Many to many foreign keys now have the default set lazily only if the relation has been accessed. This avoids storing empty arrays if the relation has not been touched.

Resolved Issues

#2730 Calling sort on a context properly updates the context's criteria. (Arthur Neves)
#2719 distinct is now available at the class level.
```
Band.distinct(:name)
```
#2714 Overriding sessions when the new session has a different database will now properly switch the database at runtime as well.
#2697 Eager loading fixed when including multiple models that inherit from the same class. (Kirill Lazarev)
#2664 In memory sorting of embedded documents now properly works when multiple fields are provided. (Neer Friedman)

3.0.24

Resolved Issues

#2879 remove_attribute on new documents no longer creates an unnecessary $unset operation.

3.0.23

Resolved Issues

#2851 Fixed BigDecimal demongoization of NaN values. (nkem)
#2841 Calling delete_all or destroy_all on an embeds many when in the middle of a parent update will now properly execute the deletion. (Arthur Neves)
#2835 Fixed clearing of persistence options in uniqueness validator.
#2826 Dynamic fields are now properly mongoized.
#2822 Marshal load of relations now properly reapplies extensions.
#2821 Autosaved relations should be duped in inheriting classes.

3.0.22

Resolved Issues

#2812 Fixed criteria on many to many relations when the base document is destroyed and the foreign key has not yet been lazy evaluated.
#2796 Don't cascade changes on has_many relations when assigning with a delete.
#2795 Fix precision on time conversions. (Tom de Bruijn)
#2794 Don't autobuild when reading a relation for validation.
#2790 becomes now copies embedded documents even if they were protected by mass assignment.
#2787 Allow becomes to replace the document in the identity map.
#2786 Fixed regressed cascading callbacks on destroy not firing.
#2784 Fixed uniqueness validation properly getting added to subclasses. (Takeshi Akima)

3.0.21

Resolved Issues

#2781 / * #2777 - Fixed issue with serialization of DateTime that was only present in Rails environments.

3.0.20

Resolved Issues

#2774 Ensure validations macros for uniqueness, presence, and associated are also available at the instance level.
#2772 Localized fields are now properly handled when cloning a document.
#2758 Mongoid.create_indexes does not fail when cannot constantize class. (Arthur Neves)
#2743 Persistence options are no longer cleared when loading revisions. (Arthur Neves)
#2741 Fix time mongoization usec rounding errors on MRI and JRuby.
#2740 Support integer keys in hash fields when using read_attribute with dot notation.
#2739 Ensure integer deserialization properly casts to integers.
#2733 Many to many relations with inverse_of: nil do not persist the inverse relation on << or push if the document is already persisted.
#2705 Fixed logic around when children can be added to the cascading callbacks list.

3.0.19

Resolved Issues

Released to revert the changes in #2703.

3.0.18

Resolved Issues

#2707 Calling find_or_create_by or find_by_initialize_by off a relation with a chained criteria or scope now properly keeps the relations intact on the new or found document.
#2699 Resetting a field now removes the name from the changed attributes list. (Subhash Bhushan)
#2683 Aliased fields are now supported when executing atomic operations from criteria. (Arthur Neves)
#2678 Calling Criteria#sum with no matching documents returns 0 instead of nil.
#2671 Matchers now correctly handle symbol keys. (Jonathan Hyman)

3.0.17

Resolved Issues

#2686 Fixed the broken Moped dependency - Moped now must be at least at version 1.2.0.

3.0.16

Resolved Issues

#2661 Implement instance level model_name for documents.
#2651 Ensure Criteria#type works properly with both symbol and string keys in the selector.
#2647 Ensure deleted? and destroyed? on paranoid documents return the same value.
#2646 Set unloaded doc in memory on enumerable targets before yielding to the block.
#2645 Take caching into consideration when asking for counts. (Arthur Nogueira Neves)
#2642 Don't batch push empty arrays on embedded documents. (Laszlo Bacsi)
#2639 Avoid extra unnecesary queries on new records when building relations off of them.
#2638 When a criteria is eager loading, calling first or last then iterating the entire results properly eager loads the full request.
#2618 Validating uniqueness now always uses string consistency by default.
#2564 Fixed infinite recursion for cases where a relation getter was overridden and called the setter from that method.
#2554 Ensure unscoped on an embeds_many does not include documents flagged for destruction.

3.0.15

Resolved Issues

#2630 Fix cascading when the metadata exists but no cascade defined.
#2625 Fix Marshal.dump and Marshal.load of proxies and criteria objects.
#2619 Fixed the classes returned by observed_classes on an observer when it is observing custom models.
#2612 DocumentNotFound errors now expose the class in the error instance.
#2610 Ensure calling first after a last that had sorting options resets the sort.
#2604 Check pulls and pushes for conflicting updates. (Lucas Souza)
#2600 Instantiate the proper class type for attributes when using multi parameter attributes. (xxswingxx)
#2598 Fixed sorting on localized fields with embedded docs.
#2588 Block defining methods for dynamic attributes that would be invalid ruby methods. (Matt Sanford)
#2587 Fix method clash with belongs_to proxies when resetting relation unloaded criteria.
#2585 Ensure session configuration options get passed to Moped as symbols.
#2584 Allow map/reduce to operate on secondaries if output is set to inline.
#2582 Ensure nil session override can never cause to access a session with name nil.
#2581 Use strong consistency when reloading documents. (Mark Kremer)

3.0.14

Resolved Issues

#2575 Prevent end of month times from rounding up since floats are not precise enough to handle usec. (Steve Valaitis)
#2573 Don't use i18n for inspection messages.
#2571 Remove blank error message from locales. (Jordan Elver)
#2568 Fix uniqueness validation for localized fields when a scope is also provided.
#2552 Ensure InvalidPath errors are raised when embedded documents try to get paths from a root selector.

3.0.13

Resolved Issues

#2548 Fix error when generating config file with a fresh app with Unicorn in the gemset.

3.0.12

Resolved Issues

#2542 Allow embedded documents using store_as to properly alias in criteria.
#2541 Ensure that the type change is correct when upcasting/downcasting a document via Document#becomes (Łukasz Bandzarewicz)
#2529 Fields on subclasses that override fields in the parent where both have defaults with procs now properly override the default in the subclass.
#2528 Aliased fields need to be duped when subclassing.
#2527 Ensure removal of docs in a has_many does a multi update when setting to an empty array.

3.0.11

Resolved Issues

#2522 Fixed Criteria#with to return the criteria and not the class.
#2518 Fix unit of work call for the identity map when using Passenger.
#2512 Ensure nested attributes destroy works with the delayed destroys introduced in 3.0.10 when multiple levels deep.
#2509 Don't hit identity map an extra time when the returned value is an empty hash. (Douwe Maan)

3.0.10

Resolved Issues

#2507 Ensure no extra db hits when eager loading has a mix of parents with and without docs. (Douwe Maan)
#2505 Ensure update and update_all from criteria properly handle aliased fields. (Dmitry Krasnoukhov)
#2504 Model#becomes properly keeps the same id.
#2498 Criteria now properly pass provided blocks though method_missing.
#2496 Embedded documents that were previously stored without ids now properly update and get assigned ids from within Mongoid.
#2494 All explicit atomic operations now properly respect aliased fields.
#2493 Use Class#name instead of Class#model_name when setting polymorphic types in case model_name has been overridden.
#2491 Removed unnecessary merge call in cascadable children.
#2485 Removing indexes now always uses strong consistency.
#2483 Versioning now handles localized fields. (Lawrence Curtis)
#2482 Store find parameters in the DocumentNotFound error.
#2481 Map/reduce aggregations now properly handle Mongo's batching of reduce jobs in groups of 100 with the state being passed through on the count.
#2476 Handle skip and limit outside of range on embeds_many relations gracefully.
#2474 Correctly detach 1-1 relations when the child is not yet loaded. (Kostyantyn Stepanyuk)
#2451 relation.deleted on embedded paranoid documents now works properly again.
#2472 Ensure update_all on embedded relations works properly when nothing is actually going to be updated.
#2469 Nullified documents on relations are now able to be re-added with the same in memory instance.
#2454 Model#as_document properly allows changes from having a relation to the relation being removed. (James Almond)
#2445 Mongoid middleware now properly supports both normal and streamed responses and properly clears the identity map for either.
#2367 Embedded documents that are to be deleted via nested attributes no longer become immediately removed from the relation in case the parent validation fails. Instead, they get flagged for destruction and then the removal occurs upon the parent passing validation and going to persist.

Note this is a behavior change, but since the API does not change and the previous behavior was incorrect and did not match AR this was able to go into a point release.

3.0.9

Resolved Issues

#2463 Fixed the broken rails g mongoid:config from a fresh repo.
#2456 The descendants cache is now reset when the document is inherited again. (Kostyantyn Stepanyuk)
#2453 Model#write_attribute now properly works with aliased fields. (Campbell Allen)
#2444 Removed extra dirty methods creation call. (Kostyantyn Stepanyuk)
#2440/\#2435 Pass mass assignment options down to children when setting via nested attributes or embedded documents.
#2439 Fixed memory leak in threaded selection of returned fields. (Tim Olsen)
mongoid/moped#82 Aliased fields now work with Criteria#distinct.
#2423 Fixed embedded document's update_all to perform the correct $set when using off a criteria.
#2414 Index definitions now respect aliased fields.
#2413 Enumerable targets now properly return enumerators when no blocks are provided. (Andrew Smith)
#2411 BigDecimal fields are properly stored as strings when mongoizing integers and floats.
#2409 Don't warn about missing mongoid.yml if configured programmatically.
#2403 Return false on update_all of an embeds many with no documents.
#2401 Bring back the ability to merge a criteria with a hash.
#2399 Reject blank id values on has_many Model#object_ids=. (Tiago Rafael Godinho)
#2393 Ensure inverse_of is respected when using polymorphic relations.
#2388 Map/reduce properly uses sort instead of orderby in the execution of the command. (Alex Tsibulya)
#2386 Allow geo haystack and bits parameters in indexes. (Bradley Rees)
#2380 Model#becomes now properly copies over dirty attributes.
#2331 Don't double push child documents when extra saves are called in an after_create callback.

3.0.8 (Yanked)

3.0.6

Resolved Issues

#2375 Uniqueness validation scoping now works with aliased fields.
#2372 Ensure that all atomic operations mongoize values before executing.
#2370 Paranoid documents now properly don't get deleted when using dependent: :restrict and an exception is raised.
#2365 Don't do anything when trying to replace an embeds_one with the same document.
#2362 Don't store inverse of field values in the database when they are not needed. (When there is not more than one polymorphic parent defined on the same class).
#2360 Cloning documents should ignore mass assignment protection rules.
#2356 When limiting fields returned in queries via only ensure that the limitation is scoped to the model.
#2353 Allow update_attribute to properly handle aliased fields.
#2348 Conversion of strings to times should raise an argument error if the string is invalid. (Campbell Allen)
#2346 Ensure belongs_to relations are evolvable when passed the proxy and not the document.
#2334 Fixed aggregation map/reduce when fields sometimes do not exist. (James McKinney)
#2330 Fixed inconsistency of #size and #length on criteria when the documents have been iterated over with a limit applied.
#2328 Ensure ordering is applied on all relation criteria if defined.
#2327 Don't execute callbacks from base document if the document cannot execute them.
#2318 Ensure setting any numeric on a Float field actually sets it as a float, even if the number provided is an integer.

3.0.5

Resolved Issues

#2313 Fixed deserialization of nil TimeWithZone fields. (nagachika)
#2311 Document#changes no longer returns nil values for Array and Hash fields that were only accessed and didn't actually change. Regression from 2.4.x.
#2310 Setting a many to many duplicate successively in memory no longer clears the inverse foreign keys.
#2309 Allow embeds_one relations to be set with hashes more than just the initial set.
#2308 Ensure documents retrieved via #find on has_many and has_and_belongs_to_many relations are kept in memory.
#2304 Default scopes now properly merge instead of overwrite when more than one is defined as per expectations with AR. (Kirill Maksimov)
#2300 Ensure reloading refreshes the document in the identity map.
#2298 Protect against many to many relations pulling a null set of ids. (Jonathan Hyman)
#2291 Fixed touch operations only to update the timestamp and the optional field, no matter what the other changes on the document are.
#1091 Allow presence validation to pass if the value is false.

3.0.4

Resolved Issues

#2280 Fix synchronization of many-to-many relations when an ordering default scope exists on either side of the association.
#2278 Criteria#update now properly updates only the first matching document, where Criteria#update_all will update all matching documents. (no flag vs multi).
#2274 When loading models, warn if error is raised but continue processing.
#2272 Don't wipe selectors or options when removing the default scope for actual nil values. Must check if key exists as well.
#2266 Restored paranoid documents are no longer flagged as destroyed. (Mario Uher)
#2263 Ensure casting of non object id foreign keys on many to many relations happens in the initial set, not at validation time.

3.0.3

Resolved Issues

#2259 Ensure subclassed documents can not be pulled from the identity map via an id of another document in the same collection with a parent or sibeling type.
#2254 $inc operations no longer convert all values to floats.
#2252 Don't fire autosave when before callbacks have terminated.
#2248 Improved the performance of exists? on criteria and relations. (Jonathan Hyman)

3.0.2

Resolved Issues

#2244 Get rid of id mass assignment warnings in nested attributes.
#2242 Fix eager loading not to load all documents when calling first or last.
#2241 Map/reduce operations now always use strong consistency since they have the potential to write to collections, most of the time.
#2238 Ensure n-n foreign key fields are flagged as resizable to prevent nil -> [] changes when using #only and updating.
#2236 Keep the instance of the document in the validations exception accessible via document or record.
#2234 Ensure validations when document is getting persisted with custom options work properly with custom options, and do not clear them out if validation passes.
#2224 Model#inc now accepts BigDecimal values.
#2216 Fixed assignment of metadata on embeds one relations when setting multiple times in a row.
#2212 Ensure errors are cleared after a save with validate: false in all situations.
#2207 When eager loading ids the query must be duped to avoid multiple iteration problems not getting the required fields.
#2204 Raise an InvalidIncludes error when passing arguments to Criteria.includes that are invalid (not relations, or more than 1 level.)

#2203 Map/Reduce now works properly in conjunction with Model#with.

Band.
  with(session: "secondary").
  where(:likes.gt => 100).
  map_reduce(map, reduce).
  out(inline: 1)

#2199 Autosave false is now respected when automatically adding presence validation. (John Nishinaga)

3.0.1

Resolved Issues

#2191 Ensure proper visibility (private) for error message generation methods.
#2187 Ensure all levels of nested documents are serialized in json.
#2184 Allow names of relations that conflict with ruby core kernel methods to pass existence checks.
#2181 Ensure .first criteria sort by ascending ids, if no other sorting criteria was provided.

3.0.0

New Features

#2151 When asking for metadata before persistence, Mongoid will now raise a Mongoid::Errors::NoMetadata error if the metadata is not present.
#2147 Model#becomes now copies over the embedded documents.
A new callback has been introduced: upsert, which runs when calling document.upsert since Mongoid does not know if the document is to be treated as new or persisted. With this come the model callbacks:
```
before_upsert
after_upsert
around_upsert
```

#2080/\#2087 The database or session that Mongoid persists to can now be overridden on a global level for cases where Model#with is not a viable option.

  Mongoid.override_database(:secondary)
  Mongoid.override_session(:secondary)

  Band.create(name: "Placebo") #=> Persists to secondary.
  band.albums.create #=> Persists to secondary.

Note that this option is global and overrides for all models on the current
thread. It is the developer's responsibility to remember to set this back
to nil if you no longer want the override to happen.

  Mongoid.override_database(nil)
  Mongoid.override_session(nil)

#1989 Criteria count, size and length now behave as Active Record with regards to database access.

`Criteria#count` will always hit the database to get the count.

`Criteria#length` and `Criteria#size` will hit the database once if the
criteria has not been loaded, and subsequent calls will return the
cached value.

If the criteria has been iterated over or loaded, `length` and `size`
will never hit the db.

#1976 Eager loading no longer produces queries when the base query returns zero results.
Model.find_by now accepts a block and will yield to the found document if it is not nil.
```
Band.find_by(name: "Depeche Mode") do |band|
  band.likes = 100
end
```

#1958/\#1798 Documents and belongs_to relations now support touch.

  class Band
    include Mongoid::Document
    include Mongoid::Timestamps::Updated
    belongs_to :label, touch: true
  end

Update the document's updated_at timestamp to the current time. This
will also update any touchable relation's timestamp as well.

  Band.first.touch

Update a specific time field along with the updated_at.

  Band.first.touch(:founded)

This fires no validations or callbacks.

Mongoid now supports MongoDB's $findAndModify command.

Band.find_and_modify("$inc" => { likes: 1 })

Band.desc(:name).only(:name).find_and_modify(
  { "$inc" => { likes: 1 }}, new: true
)

#1906 Mongoid will retrieve documents from the identity map when providing multiple ids to find. (Hans Hasselberg)
#1903 Mongoid raises an error if provided a javascript expression to a where clause on an embedded collection. (Sebastien Azimi)

Aggregations now adhere to both a Mongoid API and their enumerable counterparts where applicable.

  Band.min(:likes)
  Band.min do |a, b|
    a.likes <=> b.likes
  end

  Band.max(:likes)
  Band.max do |a, b|
    a.likes <=> b.likes
  end

Note that when providing a field name and no block, a single numeric
value will be returned, but when providing a block, a document will
be returned which has the min/max value. This is since Ruby's
Enumerable API dictates when providing a block, the matching element
is returned.

When providing a block, all documents will be loaded into memory.
When providing a symbol, the execution is handled via map/reduce on
the server.

A kitchen sink aggregation method is now provided, to get everything in in a single call for a field.

Band.aggregates(:likes)
# =>
#   {
#     "count" => 2.0,
#     "max" => 1000.0,
#     "min" => 500.0,
#     "sum" => 1500.0,
#     "avg" => 750.0
#   }

A DSL off the criteria API is now provided for map/reduce operations as a convenience.

Band.where(name: "Tool").map_reduce(map, reduce).out(inline: 1)
Band.map_reduce(map, reduce).out(replace: "coll-name")
Band.map_reduce(map, reduce).out(inline: 1).finalize(finalize)

Mongoid now uses Origin for its Criteria API. See the Origin repo and API docs for the documentation.
#1861 Mongoid now raises an AmbiguousRelationship error when it cannot determine the inverse of a relation and there are multiple potential candidates. (Hans Hasselberg)
You can now perform an explain directly from criteria.
```
Band.where(name: "Depeche Mode").explain
```
#1856 Push on one to many relations can now be chained.
```
band.albums.push(undertow).push(aenima)
```
#1842 MultiParameterAttributes now supported aliased fields. (Anton Orel)
#1833 If an embedded document is attempted to be saved with no parent defined, Mongoid now will raise a Mongoid::Errors::NoParent exception.

Added an ORM-agnostic way to get the field names

class Band
  include Mongoid::Document
  field :name, type: String
end

Band.attribute_names

#1831 find_or_create_by on relations now takes mass assignment and type options. (Tatsuya Ono)

class Band
  include Mongoid::Document
  embeds_many :albums
end

band.albums.find_or_create_by({ name: "101" }, LP)

#1818 Add capability to choose the key where your embeds_many relation is stores. (Cyril Mougel)

class User
  include Mongoid::Document
  field :name, type: String
  embeds_many :prefs, class_name: "Preference", store_as: 'my_preferences'
end

user.prefs.build(value: "ok")
user.save
# document saves in MongoDB as:
# { "name" => "foo", "my_preferences" => [{ "value" => "ok" }]}

#1806 Model.find_or_create_by and Model.find_or_initialize_by can now take documents as parameters for belongs_to relations.
```
person = Person.first
Game.find_or_create_by(person: person)
```

#1774 Relations now have a :restrict option for dependent relations which will raise an error when attempting to delete a parent that still has children on it. (Hans Hasselberg)

class Band
  include Mongoid::Document
  has_many :albums, dependent: :restrict
end

band = Band.first
band.albums << Albums.first
band.delete # Raises DeleteRestriction error.

#1764 Add method to check if field differs from the default value.

class Band
  include Mongoid::Document
  field :name, type: String, default: "New"
end

band = Band.first
band.name_changed_from_default?

#1759 Invalid fields error messages have been updated to show the source and location of the original method. The new message is:

Problem:
  Defining a field named 'crazy_method' is not allowed.
Summary:
  Defining this field would override the method 'crazy_method',
  which would cause issues with expectations around the original
  method and cause extremely hard to debug issues.
  The original method was defined in:
    Object: MyModule
    File: /path/to/my/module.rb
    Line: 8
Resolution:
  Use Mongoid.destructive_fields to see what names are
  not allowed, and don't use these names. These include names
  that also conflict with core Ruby methods on Object, Module,
  Enumerable, or included gems that inject methods into these
  or Mongoid internals.

#1753/#1649 A setter and getter for has_many relations to set its children is now provided. (Piotr Jakubowski)

class Album
  include Mongoid::Document
  has_many :engineers
end

class Engineer
  include Mongoid::Document
  belongs_to :album
end

album = Album.first
engineer = Engineer.first
album.engineer_ids = [ engineer.id ]
album.engineer_ids # Returns the ids of the engineers.

#1741 Mongoid now provides a rake task to force remove indexes for environments where Mongoid manages the index definitions and the removal should be automated. (Hans Hasselberg)
```
rake db:force_remove_indexes
rake db:mongoid:force_remove_indexes
```
#1726 Mongoid.load! now accepts an optional second argument for the environment to load. This takes precedence over any environment variable that is set if provided.
```
Mongoid.load!("/path/to/mongoid.yml", :development)
```

#1724 Mongoid now supports regex fields.

class Rule
  include Mongoid::Document
  field :pattern, type: Regexp, default: /[^abc]/
end

#1714/\#1706 Added better logging on index creation. (Hans Hasselberg)

When an index is present on a root document model:

  Creating indexes on: Model for: name, dob.

When an index is defined on an embedded model:

  Index ignored on: Address, please define in the root model.

When no index is defined, nothing is logged, and if a bad index is
defined an error is raised.

#1710 For cases when you don't want Mongoid to auto-protect the id and type attributes, you can set a configuration option to turn this off.
```
Mongoid.protect_sensitive_fields = false
```

#1685 Belongs to relations now have build_ and create_ methods.

class Comment
  include Mongoid::Document
  belongs_to :user
end

comment = Comment.new
comment.build_user # Build a new user object
comment.create_user # Create a new user object

#1684 Raise a ::Mongoid::Errors::InverseNotFound when attempting to set a child on a relation without the proper inverse_of definitions due to Mongoid not being able to determine it.

class Car
  include Mongoid::Document
  embeds_one :engine, class_name: "Motor"
end

class Motor
  include Mongoid::Document
  embedded_in :machine, class_name: "Car"
end

car = Car.new
car.engine = Motor.new # raises an InverseNotFound error.

#1680 Polymorphic relations now use *_type keys in lookup queries.

class User
  include Mongoid::Document
  has_many :comments, as: :commentable
end

class Comment
  include Mongoid::Document
  belongs_to :commentable, polymorphic: true
end

user = User.find(id)
user.comments # Uses user.id and type "User" in the query.

#1677 Support for parent separable polymorphic relations to the same parent class is now available. This only works if set from the parent side in order to know which relation the children belong to. (Douwe Maan)

class Face
  include Mongoid::Document
  has_one :left_eye, class_name: "Eye", as: :visible
  has_one :right_eye, class_name: "Eye", as: :visible
end

class Eye
  include Mongoid::Document
  belongs_to :visible, polymorphic: true
end

face = Face.new
right_eye = Eye.new
left_eye = Eye.new
face.right_eye = right_eye
face.left_eye = left_eye
right_eye.visible = face # Will raise an error.

#1650 Objects that respond to to_criteria can now be merged into existing criteria objects.

class Filter
  def to_criteria
    # return a Criteria object.
  end
end

criteria = Person.where(title: "Sir")
criteria.merge(filter)

#1635 All exceptions now provide more comprehensive errors, including the problem that occurred, a detail summary of why it happened, and potential resolutions. Example:

(Mongoid::Errors::DocumentNotFound)
Problem:
  Document not found for class Town with
  id(s) [BSON::ObjectId('4f35781b8ad54812e1000001')].
Summary:
  When calling Town.find with an id or array of ids,
  each parameter must match a document in the database
  or this error will be raised.
Resolution:
  Search for an id that is in the database or set the
  Mongoid.raise_not_found_error configuration option to
  false, which will cause a nil to be returned instead
  of raising this error.

#1616 Model.find_by added which takes a hash of arguments to search for in the database. If no single document is returned a DocumentNotFound error is raised. (Piotr Jakubowski)
```
Band.find_by(name: "Depeche Mode")
```

#1606 Mongoid now enables autosave, like Active Record, when adding an accepts_nested_attributes_for to a relation.

class Band
  include Mongoid::Document
  has_many :albums
  accepts_nested_attributes_for :albums # This enables the autosave.
end

#1477 Mongoid now automatically protects the id and type attributes from mass assignment. You can override this (not recommended) by redefining them as accessible.
```
class Band
  include Mongoid::Document
  attr_accessible :id, :_id, :_type
end
```

#1459 The identity map can be disabled now for specific code execution by passing options to the unit of work.

Mongoid.unit_of_work(disable: :all) do
  # Disables the identity map on all threads for the block.
end

Mongoid.unit_of_work(disable: :current) do
  # Disables the identity map on the current thread for the block.
end

Mongoid.unit_of_work do
  # Business as usual.
end

#1355 Associations now can have safety options provided to them on single document persistence operations.

band.albums.with(safe: true).push(album)
band.albums.with(safe: true).create(name: "Smiths")

album.with(safe: true).create_producer(name: "Flood")

#1348 Eager loading is now supported on many-to-many relations.
#1292 Remove attribute now unsets the attribute when the document is saved instead of setting to nil.
```
band = Band.find(id)
band.remove_attribute(:label) # Uses $unset when the document is saved.
```
#1291 Mongoid database sessions are now connected to lazily, and are completely thread safe. If a new thread is created, then a new database session will be created for it.
#1291 Mongoid now supports any number of database connections as defined in the mongoid.yml. For example you could have a local single server db, a multi availability zone replica set, and a shard cluster all in the same application environment. Mongoid can connect to any session at any point in time.

#1291 Mongoid now allows you to persist to whatever database or collection you like at runtime, on a per-query or persistence operation basis by using with.

Band.with(collection: "artists").create(name: "Depeche Mode")
band.with(database: "secondary).save!
Band.with(collection: "artists").where(name: "Depeche Mode")

#1291 You can now configure on a per-model basis where its documents are stored with the new and improved store_in macro.

  class Band
    include Mongoid::Document
    store_in collection: "artists", database: "secondary", session: "replica"
  end

This can be overridden, of course, at runtime via the `with` method.

#1212 Embedded documents can now be popped off a relation with persistence.

band.albums.pop # Pop 1 document and persist the removal.
band.albums.pop(3) # Pop 3 documents and persist the removal.

#1188 Relations now have existence predicates for simplified checking if the relation is blank or not. (Andy Morris)

class Band
  include Mongoid::Document
  embeds_many :albums
  embeds_one :label
end

band = Band.new
band.albums?
band.has_albums?
band.label?
band.has_label?

#1188 1-1 relations now have an :autobuild option to indicate if the relation should automatically be build with empty attributes upon access where the relation currently does not exist. Works on embeds_one, embedded_in, has_one, belongs_to. (Andy Morris)

  class Band
    include Mongoid::Document
    has_one :label, autobuild: true
  end

  band = Band.new
  band.label # Returns a new label with empty attributes.

When using existence checks, autobuilding will not execute.

  band = Band.new
  band.label? # Returns false, does not autobuild on a check.
  band.has_label? # Returns false, does not autobuild on a check.

#1081 Mongoid indexes both id and type as a compound index when providing index: true to a polymorphic belongs_to.

class Comment
  include Mongoid::Document

  # Indexes commentable_id and commentable_type as a compound index.
  belongs_to :commentable, polymorphic: true, index: true
end

#1053 Raise a ::Mongoid::Errors::UnknownAttribute instead of no method when attempting to set a field that is not defined and allow dynamic fields is false. (Cyril Mougel)

Mongoid.allow_dynamic_fields = false

class Person
  include Mongoid::Document
  field :title, type: String
end

Person.new.age = 50 # raises the UnknownAttribute error.

#772 Fields can now be flagged as readonly, which will only let their values be set when the document is new.

  class Band
    include Mongoid::Document
    field :name, type: String
    field :genre, type: String

    attr_readonly :name, :genre
  end

Readonly values are ignored when attempting to set them on persisted
documents, with the exception of update_attribute and remove_attribute,
where errors will get raised.

  band = Band.create(name: "Depeche Mode")
  band.update_attribute(:name, "Smiths") # Raises ReadonlyAttribute error.
  band.remove_attribute(:name) # Raises ReadonlyAttribute error.

Major Changes (Backwards Incompatible)

Polymorphic relations can not have ids other than object ids. This is because Mongoid cannot properly figure out in an optimized way what the various classes on the other side of the relation store their ids as, as they could potentially all be different.

This was not allowed before, but nowhere was it explicitly stated.
#2039 Validating presence of a relation now checks both the relation and the foreign key value.

Indexing syntax has changed. The first parameter is now a hash of name/direction pairs with an optional second hash parameter for additional options.

Normal indexing with options, directions are either 1 or -1:

  class Band
    include Mongoid::Document
    field :name, type: String

    index({ name: 1 }, { unique: true, background: true })
  end

Geospacial indexing needs "2d" as its direction.

  class Venue
    include Mongoid::Document
    field :location, type: Array

    index location: "2d"
  end

Custom serializable fields have revamped. Your object no longer should include Mongoid::Fields::Serializable - instead it only needs to implement 3 methods: #mongoize, .demongoize and .evolve.

`#mongoize` is an instance method that transforms your object into
a mongo-friendly value.

`.demongoize` is a class method, that can take some data from mongo
and instantiate and object of your custom type.

`.evolve` is a class method, that can take any object, and
transform it for use in a `Mongoid::Criteria`.

An example of an implementation of this for `Range`:

  class Range

    def mongoize
      { "min" => first, "max" => last }
    end

    class << self

      def demongoize(object)
        Range.new(object["min"], object["max"])
      end

      def evolve(object)
        { "$gte" => object.first, "$lte" => object.last }
      end
    end
  end

Document#changes is no longer a hash with indifferent access.
after_initialize callbacks no longer cascade to children if the option is set.

#1865 count on the memory and mongo contexts now behave exactly the same as Ruby's count on enumerable, and can take an object or a block. This is optimized on the mongo context not to load everything in memory with the exception of passing a block.

  Band.where(name: "Tool").count
  Band.where(name: "Tool").count(tool) # redundant.
  Band.where(name: "Tool") do |doc|
    doc.likes > 0
  end

Note that although the signatures are the same for both the memory and
mongo contexts, it's recommended you only use the block syntax for the
memory context since the embedded documents are already loaded into
memory.

Also note that passing a boolean to take skip and limit into account
is no longer supported, as this is not necessarily a useful feature.

The autocreate_indexes configuration option has been removed.
Model.defaults no longer exists. You may get all defaults with a combination of Model.pre_processed_defaults and Model.post_processed_defaults.
```
Band.pre_processed_defaults
Band.post_processed_defaults
```

Model.identity and Model.key have been removed. For custom ids, users must now override the _id field.

When the default value is a proc, the default is applied *after* all
other attributes are set.

  class Band
    include Mongoid::Document
    field :_id, type: String, default: ->{ name }
  end

To have the default applied *before* other attributes, set `:pre_processed`
to true.

  class Band
    include Mongoid::Document
    field :_id,
      type: String,
      pre_processed: true,
      default: ->{ BSON::ObjectId.new.to_s }
  end

Custom application exceptions in various languages has been removed, along with the Mongoid.add_language feature.
Mongoid no longer supports 1.8. MRI 1.9.3 and higher, or JRuby 1.6 and higher in 1.9 mode are only supported.
#1734 When searching for documents via Model.find with multiple ids, Mongoid will raise an error if not all ids are found, and tell you what the missing ones were. Previously the error only got raised if nothing was returned.
#1675 Adding presence validation on a relation now enables autosave. This is to ensure that when a new parent object is saved with a new child and marked is valid, both are persisted to ensure a correct state in the database.
#1491 Ensure empty translations returns an empty hash on access.
#1484 Model#has_attribute? now behaves the same as Active Record.
#1471 Mongoid no longer strips any level of precision off of times.
#1475 Active support's time zone is now used by default in time serialization if it is defined.
#1342 Model.find and model.relation.find now only take a single or multiple ids. The first/last/all with a conditions hash has been removed.
#1291 The mongoid.yml has been revamped completely, and upgrading existing applications will greet you with some lovely Mongoid specific configuration errors. You can re-generate a new mongoid.yml via the existing rake task, which is commented to an insane degree to help you with all the configuration possibilities.

#1291 The persist_in_safe_mode configuration option has been removed. You must now tell a database session in the mongoid.yml whether or not it should persist in safe mode by default.

production:
  sessions:
    default:
      database: my_app_prod
      hosts:
        - db.app.com:27018
        - db.app.com:27019
      options:
        consistency: :eventual
        safe: true

#1291 safely and unsafely have been removed. Please now use with to provide safe mode options at runtime.

Band.with(safe: true).create
band.with(safe: { w: 3 }).save!
Band.with(safe: false).create!

#1270 Relation macros have been changed to match their AR counterparts: only :has_one, :has_many, :has_and_belongs_to_many, and :belongs_to exist now.
#1268 Model#new? has been removed, developers must now always use Model#new_record?.

#1182 A reload is no longer required to refresh a relation after setting the value of the foreign key field for it. Note this behaves exactly as Active Record.

If the id is set, but the document for it has not been persisted, accessing
the relation will return empty results.

If the id is set and its document is persisted, accessing the relation
will return the document.

If the id is set, but the base document is not saved afterwards, then
reloading will return the document to its original state.

#1093 Field serialization strategies have changed on Array, Hash, Integer and Boolean to be more consistent and match AR where appropriate.

Serialization of arrays calls `Array.wrap(object)`
Serialization of hashes calls `Hash[object]` (to_hash on the object)
Serialization of integers always returns an int via `to_i`
Serialization of booleans defaults to false instead of nil.

#933 :field.size has been renamed to :field.count in criteria for $size not to conflict with Symbol's size method.

#829/\#797 Mongoid scoping code has been completely rewritten, and now matches the Active Record API. With this backwards incompatible change, some methods have been removed or renamed.

Criteria#as_conditions and Criteria#fuse no longer exist.

Criteria#merge now only accepts another object that responds to
`to_criteria`.

Criteria#merge! now merges in another object without creating a new
criteria object.

  Band.where(name: "Tool").merge!(criteria)

Named scopes and default scopes no longer take hashes as parameters.
From now on only criteria and procs wrapping criteria will be
accepted, and an error will be raised if the arguments are incorrect.

  class Band
    include Mongoid::Document

    default_scope ->{ where(active: true) }
    scope :inactive, where(active: false)
    scope :invalid, where: { valid: false } # This will raise an error.
  end

The 'named_scope' macro has been removed, from now on only use 'scope'.

Model.unscoped now accepts a block which will not allow default scoping
to be applied for any calls inside the block.

  Band.unscoped do
    Band.scoped.where(name: "Ministry")
  end

Model.scoped now takes options that will be set directly on the criteria
options hash.

  Band.scoped(skip: 10, limit: 20)

#463 Document#upsert is no longer aliased to Document#save and now actually performs a proper MongoDB upsert command when called. If you were using this method before and want the same behavior, please switch to save.
```
band = Band.new(name: "Tool")
band.upsert #=> Inserts the document in the database.
band.name = "Placebo"
band.upsert #=> Updates the existing document.
```

Resolved Issues

#2166 Criteria#from_map_or_db strips type selection when eager loading since it will check if the type is correct after.
#2129 Fixed sorting for all fields on embeds many relations.
#2124 Fixed default scope and deleted scope on paranoid documents.
#2122 Allow embedded documents to sort on boolean fields.
#2119 Allow Criteria#update_all to accept atomic ops and normal sets.
#2118 Don't strip any precision during DateTime -> Time conversions.
#2117 Ensure embeds one relations have callbacks run when using nested attributes.
#2110 Model#touch now works properly on embedded documents.
#2100 Allow atomic operations to properly execute on paranoid documents that have a deleted_at set.
#2089 Allow proper separation of mongoization and evolving with respect to foreign keys.
#2088 Allow finds by string ids to pull from the identity map if the ids are stored as object ids.
#2085 Allow demongoization of floats and ints to big decimals.
#2084 Don't cascade if metadata does not exist.
#2078 Calling Model#clone or Model#dup now properly sets attributes as dirty.
#2070 Allow for updated_at to be overridden manually for new documents that also have a created_at.
#2041 Don't hit the database multiple times on relation access after an eager load returned zero documents.
#1997 Cascading callbacks should be able to halt the callback chain when terminating.
#1972 added, loaded, and unloaded can now be valid scope names on a document that is part of a 1-n relation.
#1952/#1950 #all_in behavior on embedded documents now properly matches root documents when passing an empty array. (Hans Hasselberg)
#1941/#1939 Model.find_by now returns nil if raise not found error is set to false. (Hans Hasselberg)
#1859/#1860 Model#remove_attribute now properly unsets on embedded documents. (Anton Onyshchenko)
#1852 Ensure no infinite recursion on cascading callbacks. (Ara Howard)
#1823 Relation#includes? now properly works with identity map enabled.
#1810 Model#changed? no longer returns true when hash and array fields have only been accessed.
#1876/\#1782 Allow dot notation in embeds many criteria queries. (Cyril Mougel)
#1745 Fixed batch clear to work within attribute setting.
#1718 Ensure consistency of #first/#last in relations - they now always match first/last in the database, but opts for in memory first.
#1692/\#1376 Model#updateattributes and Model#update_attributes! now accept assignment options. (Hans Hasselberg)
#1688/\#1207 Don't require namespacing when providing class name on relation macros inside the namespace. (Hans Hasselberg)
#1665/\#1672 Expand complex criteria in nested criteria selectors, like #matches. (Hans Hasselberg)
#1335 Don't add id sorting criteria to first/last is there is already sorting options on the criteria.
#1321 Referenced many enumerable targets are now hash-backed, preventing duplicates in a more efficient manner.
#1135 DateTimes now properly get time zones on deserialization.
#1031 Mongoid now serializes values in Array fields to their proper Mongo-friendly values when possible.
#685 Attempting to use versioning with embedded documents will now raise a proper error alerting the developer this is not allowed.

2.6.0

New Features

#2709 Backported the touch functionality from Mongoid 3.

2.5.2

Resolved Issues

#2502 Fixed cache key to properly handle when the document does not include Mongoid::Timestamps::Updated. (Arthur Nogueira Neves)

2.5.1

Resolved Issues

#2492 Backport cascading callbacks performance and memory fixes from 3.0.0-stable.
#2464 Backport the nested attributes fix for keeping many relations in memory when updating attributes. (Chris Thompson)

2.5.0

New Features

This is a release to support the 1.7.0 and higher Mongo and BSON gems and resolves issues that kept the 2.4.x series locked below 1.6.2

2.4.12

Resolved Issues

#2178 Ensure destroy callbacks are run post replacement of an embeds one relation.
#2169 Allow saves to pass when documents are destroyed after the save in a callback.
#2144 Uniqueness validation on paranoid documents now properly scopes.
#2127 Don't unbind parents of embedded documents mid nested attributes deletion.

2.4.11

Resolved Issues

This release forces a cap on the mongo driver version at 1.6.2 due to changes in the Mongo::Connection.from_uri API not allowing valid connection options anymore.
#2040 Fixed bad interpolation for locale presence validation.
#2038 Allow inverse relations to be determined by foreign keys alone if defined on both sides, not just an inverse_of declaration.
#2023 Allow serialization of dynamic types that conflict with core Ruby methods to still be serialized.
#2008 Presence validation should hit the db to check validity if the relation in memory is blank.
#2006 Allow excluding only the _id field post execution of an #only call.

2.4.10

Resolved Issues

#2003 Don't fail on document generation when an embedded document was stored as nil in the database.
#1997 Don't delete paranoid embedded docs via nested attributes when a before_destroy callback returns false.
#1994 dependent: :delete only hits the database once now for one to many and many to many relations instead of once for each document.
#1987 Don't double-insert documents into identity map when eager loading twice inside the unit of work.
#1953 Uniqueness validation now works on localized fields.
#1936 Allow setting n levels deep embedded documents atomically without conflicting mods when not using nested attributes or documents themselves in an update call from the parent.
#1957/\#1954 Ensure database name is set with inheritance. (Hans Hasselberg)

2.4.9

Resolved Issues

#1943 Ensure numericality validation works for big decimals.
#1938 Length validation now works with localized fields.
#1936 Conflicting pushes with other pushes is now properly handled.
#1933 Proxy#extend should delegate through to the target, where extending the proxy itself is now handled through Proxy#proxy_extend.
#1930 Ensure complex criteria are expanded in all where clauses. (Hans Hasselberg)
#1928 Deletion of embedded documents via nested attributes now performs a $pull with id match criteria instead of a $pullAll to cover all cases. Previously newly added defaults to documents that had already persisted could not be deleted in this matter since the doc did not match what was in the database.
#1924/\#1917 Fix pushing to embedded relations with default scopes not scoping on the new document. (Hans Hasselberg)
#1922/\#1919 Dropping collections unmemoizes the internally wrapped collection, in order to ensure when defining capped collections that they are always recreated as capped. (Hans Hasselberg)
#1916/\#1913 Uniqueness validation no longer is affected by the default scope. (Hans Hasselberg)
#1943 Ensure numericality validation works for big decimals.

2.4.8

Resolved Issues

#1892 When getting not master operation error, Mongoid should reconnect before retrying the operation.
#1887 Don't cascade callbacks to children that don't have the callback defined.
#1882 Don't expand duplicate id criterion into an $and with duplicate selections.
#1878 Fixed default application values not to apply in certain only or without selection on iteration, not just first and last.
#1874 Fixed the reject all blank proc constant to handle values properly with a destroy non blank value. (Stefan Daschek)
#1869/\#1868 Delayed atomic sets now uses the atomic path instead of the metadata name to fix multiple level embedding issues. (Chris Micacchi provided specs)
#1866 Post processed defaults (procs) should be applied post binding of the child in a relation.build.

2.4.7

Resolved Issues

Ensure reloading of embedded documents retains reference to the parent.
#1837 Always pass symbol options to the driver.
#1836 Ensure relation counts pick up persisted document that have not had the foreign key link persisted.
#1820 Destroying embedded documents in an embeds_many should also removed the document from the underlying _unscoped target and reindex the relation.
#1814 Don't cascade callbacks on after_initialize.
#1800 Invalid options for the Mongo connection are now filtered out.
#1785 Case equality has been fixed to handle instance checks properly.

2.4.6

Resolved Issues

#1772 Allow skip and limit to convert strings to integers. (Jean Boussier)
#1767 Model#update_attributes accepts mass assignment options again. (Hans Hasselberg)
#1762 Criteria#any_of now properly handles localized fields.
#1758 Metadata now returns self on options for external library support.
#1757 Ensure serialization converts any attribute types to the type defined by the field.
#1756 Serializable hash options should pass through to embedded docs.

2.4.5

Resolved Issues

#1751 Mongoid's logger now responds to level for Ruby logging API compatibility.
#1744/#1750 Sorting works now for localized fields in embedded documents using the criteria API. (Hans Hasselberg)
#1746 Presence validation now shows which locales were empty for localized fields. (Cyril Mougel)
#1727 Allow dot notation in embedded criteria to work on both embeds one and embeds many. (Lyle Underwood)
#1723 Initialize callbacks should cascade through children without needing to determine if the child is changed.
#1715 Serializable hashes are now consistent on inclusion of embedded documents per or post save.
#1713 Fixing === checks when comparing a class with an instance of a subclass.
#1495 Callbacks no longer get the 'super called outside of method` errors on busted 1.8.7 rubies.

2.4.4

Resolved Issues

#1705 Allow changing the order of many to many foreign keys.
#1703 Updated at is now versioned again. (Lucas Souza)
#1686 Set the base metadata on unbind as well as bind for belongs to relations.
#1681 Attempt to create indexes for models without namespacing if the namespace does not exist for the subdirectory.
#1676 Allow eager loading to work as a default scope.
#1665/\#1672 Expand complex criteria in nested criteria selectors, like #matches. (Hans Hasselberg)
#1668 Ensure Mongoid logger exists before calling warn. (Rémy Coutable)
#1661 Ensure uniqueness validation works on cloned documents.
#1659 Clear delayed atomic sets when resetting the same embedded relation.
#1656/\#1657 Don't hit database for uniqueness validation if BOTH scope and attribute hasn't changed. (priyaaank)
#1205/\#1642 When limiting fields returned from the database via Criteria#only and Criteria#without and then subsequently saving the document. Default values no longer override excluded fields.

2.4.3

Resolved Issues

#1647 DateTime serialization when already in UTC does not convert to local time.
#1641/\#1639 Mongoid.observer.disable :all now behaves as AR does.
#1640 Update consumers should be tied to the name of the collection they persist to, not the name of the class.
#1637/\#1636 Scopes no longer modify parent class scopes when subclassing. (Hans Hasselberg)
#1629 $all and $in criteria on embedded many relations now properly handles regex searches and elements of varying length. (Douwe Maan)
#1623/\#1634 Default scopes no longer break Mongoid::Versioning. (Hans Hasselberg)
#1605 Fix regression of rescue responses, Rails 3.2

2.4.2

Resolved Issues

#1628 _type field can once again be included in serialization to json or xml as a global option with include_type_for_serialization. (Roman Shterenzon)
#1627 Validating format now works properly with localized fields. (Douwe Maan)
#1617 Relation proxy methods now show up in Mongoid's list of prohibited fields.
#1615 Allow a single configuration of host and port for all spec runs, overridden by setting MONGOID_SPEC_HOST and MONGOID_SPEC_PORT env vars.
#1610 When versioning paranoid documents and max version is set, hard delete old versions from the embedded relation.
#1609 Allow connection retry during cursor iteration as well as all other operations.
#1608 Guard against no method errors when passing ids in nested attributes and the documents do not exist.
#1605 Remove deprecation warning on rescue responses, Rails 3.2
#1602 Preserve structure of $and and $or queries when typecasting.
#1600 Uniqueness validation no longer errors when provided a relation.
#1599 Make sure enumerable targets yield to what is in memory first when performing #each, not always the unloaded first.
#1597 Fix the ability to change the order of array fields with the same elements.
#1590 Allow proper serialization of boolean values in criteria where the field is nested inside an array.

2.4.1

Resolved Issues

#1593 Arrays on embedded documents now properly atomically update when modified from original version.
#1592 Don't swallow exceptions from index generation in the create_indexes rake task.
#1589 Allow assignment of empty array to HABTM when no documents are yet loaded into memory.
#1587 When a previous value for an array field was an explicit nil, it can now be reset atomically with new values.
#1585 Model#respond_to? returns true now for the setter when allowing dynamic fields.
#1582 Allow nil values to be set in arrays.
#1580 Allow arrays to be set to nil post save, and not just empty.
#1579 Don't call #to_a on individual set field elements in criterion.
#1576 Don't hit database on uniqueness validation if the field getting validated has not changed.
#1571 Aliased fields get all the dirty attribute methods and all getters and setters for both the original name and the alias. (Hans Hasselberg)
#1568 Fallback to development environment with warning when no env configured.
#1565 For fields and foreign keys with non-standard Ruby or database names, use define_method instead of class_eval for creating the accessors and dirty methods.
#1557 Internal strategy class no longer conflicts with models.
#1551 Parent documents now return true for Model#changed? if only child (embedded) documents have changed.
#1547 Resetting persisted children from a parent save when new waits until post callbacks, mirroring update functionality.
#1536 Eager loading now happens when calling first or last on a criteria if inclusions are specified.

2.4.0

New Features

Ranges can now be passed to #where criteria to create a $gte/$lte query under the covers. Person.where(dob: start_date...end_date)
Custom serializable fields can now override #selection to provide customized serialization for criteria queries.
#1544 Internals use Array.wrap instead of to_a now where possible.
#1511 Presence validation now supports localized fields. (Tiago Rafael Godinho)
#1506 Model.set will now accept false and nil values. (Marten Veldthuis)
#1505 Model.delete_all/destroy_all now take either a :conditions hash or the attributes directly.
#1504 Model.recursively_embeds_many now accepts a :cascade_callbacks option. (Pavel Pravosud)
#1496 Mongoid now casts strings back to symbols for symbol fields that get saved as strings by another application.
#1454, #900 Associations now have an after_build callback that gets executed after .build or build_ methods are called. (Jeffrey Jones, Ryan Townsend)
#1451 Ranges can now be any range value, not just numbers. (aupajo)
#1448 Localization is now used when sorting. (Hans Hasselberg)
#1422 Mongoid raises an error at yaml load if no environment is found. (Tom Stuart)
#1413 $not support added to criteria symbol methods. (Marc Weil)
#1403 Added configuration option scope_overwrite_exception which defaults to false for raising an error when defining a named scope with the same name of an existing method. (Christoph Grabo)
#1388 model.add_to_set now supports adding multiple values and performs an $addToSet with $each under the covers. (Christian Felder)
#1387 Added Model#cache_key for use in Rails caching. (Seivan Heidari)
#1380 Calling Model.find(id) will now properly convert to and from any type based on the type of the _id field.
#1363 Added fallbacks and default support to localized fields, and added ability to get and set all translations at once.
#1362 Aliased fields now properly typecast in criteria.
#1337 Array fields, including HABTM many foreign keys now have smarter dirty checking and no longer perform a simple $set if the array has changed. If items have only been added to the array, it performs a $pushAll. If items have only been removed, it performs a $pullAll. If both additions and removals have occurred it performs a $set to avoid conflicting mods.

Resolved Issues

Calling Document#as_document on a frozen document on Rubinius returns the attributes instead of nil.
#1554 Split application of default values into proc/non-procs, where non-procs get executed immediately during instantiation, and procs get executed after all other values are set.
#1553 Combinations of adding and removing values from an array use a $set on the current contents of the array, not the new values.
#1546 Dirty changes should be returned in a hash with indifferent access.
#1542 Eager loading now respects the options (ie skip, limit) provided to the criteria when fetch the associations.
#1530 Don't duplicate added values to arrays via dirty tracking if the array is a foreign key field.
#1529 Calling unscoped on relational associations now works properly.
#1524 Allow access to relations in overridden field setters by pre-setting foreign key default values.
#1523 Allow disabling of observers via disable. (Jonas Schneider)
#1522 Fixed create indexes rake task for Rails 3.2. (Gray Manley)
#1517 Fix Mongoid documents to properly work with RSpec's stub_model. (Tiago Rafael Godinho)
#1516 Don't duplicate relational many documents on bind.
#1515 Mongoid no longer attempts to serialize custom fields on complex criteria by default.
#1503 Has many relation substitution now handles any kind of mix of existing and new docs.
#1502 Nested attributes on embedded documents respects if the child is paranoid.
#1497 Use provided message on failing uniqueness validation. (Justin Etheredge)
#1491 Return nil when no default set on localized fields. (Tiago Rafael Godinho)
#1483 Sending module includes at runtime which add new fields to a parent document, also have the fields added to subclasses.
#1482 Applying new sorting options does not merge into previously chained criteria. (Gerad Suyderhoud)
#1481 Fix invalid query when accessing many-to-many relations before defaults are set.
#1480 Mongoid's internal serialized field types renamespaced to Internal in order to not conflict with ruby core classes in custom serializable types.
#1479 Don't duplicate ids on many-to-many when using create or create!
#1469 When extract_id returns nil, get the document out of the identity map by the criteria selector.
#1467 Defining a field named metadata now properly raises an invalid field error.
#1463 Batch insert consumers are now scoped to collection to avoid persistence of documents to other collections in callbacks going to the wrong place.
#1462 Assigning has many relations via nested attributes *_attributes= does not autosave the relation.
#1461 Fixed serialization of foreign key fields in complex criteria not to escape the entire hash.
#1458 Versioning no longer skips fields that have been protected from mass assignment.
#1455, #1456 Calling destroy on any document now temporarily marks it as flagged for destroy until the operation is complete. (Nader Akhnoukh)
#1453 Model#to_key should return a value when the document is destroyed.
#1449 New documents no longer get persisted when replaced on a has one as a side effect. (jasonsydes)
#1439 embedded? should return true when relation defined as cyclic.
#1433 Polymorphic nested attributes for embedded and relational 1-1 now update properly.
#1426 Frozen documents can now be cloned. (aagrawal2001)
#1382 Raise proper error when creating indexes via rake task if index definition is incorrect. (Mathieu Ravaux)
#1381, #1371 The identity map now functions properly with inherited documents. (Paul Canavese)
#1370 Split concat on embedded arrays into its own method to handle the batch processing due to after callback run execution issues.
#1366 Array and hash values now get deep copied for dirty tracking.
#1359 Provide ability to not have default scope applied to all named scopes via using lambdas.
#1333 Fixed errors with custom types that exist in namespaces. (Peter Gumeson)
#1259 Default values are treated as dirty if they differ from the database state.
#1255 Ensure embedded documents respect the defined default scope.

2.3.4

#1445 Prevent duplicate documents in the loaded array on the target enumerable for relational associations.
#1442 When using create_ methods for has one relations, the appropriate destructive methods now get called when replacing an existing document.
#1431 Enumerable context should add to the loaded array post yield, so that methods like #any? that short circuit based on the value of the block dont falsely have extra documents.
#1418 Documents being loaded from the database for revision purposes no longer get placed in the identity map.
#1399 Allow conversion of strings to integers in foreign keys where the id is defined as an int.
#1397 Don't add default sorting criteria on first if they sort criteria already exists.
#1394 Fix exists? to work when count is greater than 1. (Nick Hoffman)
#1392 Return 0 on aggregation functions where field is nonexistent.
#1391 Uniqueness validation now works properly on embedded documents that are using primary key definitions.
#1390 When _type field is lower case class camelize before constantizing.
#1383 Fix cast on read for serializable fields that are subclassed.
#1357 Delayed atomic sets from update_attributes on embedded documents multiple levels deep now properly persist.
#1326 Ensure base document on HABTM gets its keys saved after saving a newly build child document.
#1301 Don't overwrite base metadata on embedded in relations if already set.
#1221 HABTM with inverse nil is allowed again on embedded documents.
#1208 Don't auto-persist child documents via the setter when setting from an embedded_in.
#791 Root document updates its timestamps when only embedded documents have changed.

2.3.3

Resolved Issues

#1386 Lowered mongo/bson dependency to 1.3
#1377 Fix aggregation functions to properly handle nil or undefined values. (Maxime Garcia)
#1373 Warn if a scope overrides another scope.
#1372 Never persist when binding inside of a read attribute for validation.
#1364 Fixed reloading of documents with non bson object id ids.
#1360 Fixed performance of Mongoid's observer instantiation by hooking into Active Support's load hooks, a la AR.
#1358 Fixed type error on many to many synchronization when inverse_of is set to nil.
#1356 $in criteria can now be chained to non-complex criteria on the same key without error.
#1350, #1351 Fixed errors in the string conversions of double quotes and tilde when parametrizing keys.
#1349 Mongoid documents should not blow up when including Enumerable. (Jonas Nicklas)

2.3.2

Resolved Issues

#1347 Fix embedded matchers when provided a hash value that does not have a modifier as a key.
#1346 Dup default sorting criteria when calling first/last on a criteria.
#1343 When passing no arguments to Criteria#all_of return all documents. (Chris Leishman)
#1339 Ensure destroy callbacks are run on cascadable children when deleting via nested attributes.
#1324 Setting inverse_of: nil on a many-to-many referencing the same class returns nil for the inverse foreign key.
#1323 Allow both strings and symbols as ids in the attributes array for nested attributes. (Michael Wood)
#1312 Setting a logger on the config now accepts anything that quacks like a logger.
#1297 Don't hit the database when accessing relations if the base is new.
#1239 Allow appending of referenced relations in create blocks, post default set.
#1236 Ensure all models are loaded in rake tasks, so even in threadsafe mode all indexes can be created.
#736 Calling #reload on embedded documents now works properly.

2.3.1

Resolved Issues

#1338 Calling #find on a scope or relation checks that the document in the identity map actually matches other scope parameters.
#1321 HABTM no longer allows duplicate entries or keys, instead of the previous inconsistencies.
#1320 Fixed errors in perf benchmark.
#1316 Added a separate Rake task "db:mongoid:drop" so Mongoid and AR can coexist. (Daniel Vartanov)
#1311 Fix issue with custom field serialization inheriting from hash.
#1310 The referenced many enumerable target no longer duplicates loaded and added documents when the identity map is enabled.
#1295 Fixed having multiple includes only execute the eager loading of the first.
#1287 Fixed max versions limitation with versioning.
#1277 attribute_will_change! properly flags the attribute even if no change occurred.
#1063 Paranoid documents properly run destroy callbacks on soft destroy.
#1061 Raise ::Mongoid::Errors::InvalidTime when time serialization fails.
#1002 Check for legal bson ids when attempting conversion.
#920 Allow relations to be named target.
#905 Return normalized class name in metadata if string was defined with a prefixed ::.
#861 accepts_nested_attributes_for is no longer needed to set embedded documents via a hash or array of hashes directly.
#857 Fixed cascading of dependent relations when base document is paranoid.
#768 Fixed class_attribute definitions module wide.
#408 Embedded documents can now be soft deleted via Mongoid::Paranoia.

2.3.0

New Features

Mongoid now supports basic localized fields, storing them under the covers as a hash of locale => value pairs. field :name, localize: true
#1275 For applications that default safe mode to true, you can now tell a single operation to persist without safe mode via #unsafely: person.unsafely.save, Person.unsafely.create. (Matt Sanders)
#1256 Mongoid now can create indexes for models in Rails engines. (Caio Filipini)
#1228 Allow pre formatting of composite keys by passing a block to #key. (Ben Hundley)
#1222 Scoped mass assignment is now supported. (Andrew Shaydurov)
#1196 Timestamps can now be turned off on a call-by-call basis via the use of #timeless: person.timeless.save, Person.timeless.create(:title => "Sir").
#1103 Allow developers to create their own custom complex criteria. (Ryan Ong)
Mongoid now includes all defined fields in serializable_hash and to_json results even if the fields have no values to make serialized documents easier to use by ActiveResource clients.
Support for MongoDB's $and operator is now available in the form of: Criteria#all_of(*args) where args is multiple hash expressions.
#1250, #1058 Embedded documents now can have their callbacks fired on a parent save by setting :cascade_callbacks => true on the relation. (pyromanic, Paul Rosania, Jak Charlton)

Major Changes

Mongoid now depends on Active Model 3.1 and higher.
Mongoid now depends on the Mongo Ruby Driver 1.4 and higher.
Mongoid requires MongoDB 2.0.0 and higher.

Resolved Issues

#1308 Fixed scoping of HABTM finds.
#1300 Namespaced models should handle recursive embedding properly.
#1299 Self referenced documents with versioning no longer fail when inverse_of is not defined on all relations.
#1296 Renamed internal building method to _building.
#1288, #1289 _id and updated_at should not be part of versioned attributes.
#1273 Mongoid.preload_models now checks if preload configuration option is set, where Mongoid.load_models always loads everything. (Ryan McGeary)
#1244 Has one relations now adhere to default dependant behavior.
#1225 Fixed delayed persistence of embedded documents via $set.
#1166 Don't load config in Railtie if no env variables defined. (Terence Lee)
#1052 alias_attribute now works again as expected.
#939 Apply default attributes when upcasting via #becomes. (Christos Pappas)
#932 Fixed casting of integer fields with leading zeros.
#948 Reset version number on clone if versions existed.
#763 Don't merge $in criteria arrays when chaining named scopes.
#730 Existing models that have relations added post persistence of originals can now have new relations added with no migrations.
#726 Embedded documents with compound keys not validate uniqueness correctly.
#582 Cyclic non embedded relations now validate uniqueness correctly.
#484 Validates uniqueness with multiple scopes of all types now work properly.
Deleting versions created with Mongoid::Versioning no longer fires off dependent cascading on relations.

2.2.5

This was a small patch release to address 2.2.x Heroku errors during asset compilation.

2.2.4

#1377 Fix aggregation functions to properly handle nil or undefined values. (Maxime Garcia)
#1373 Warn if a scope overrides another scope.
#1372 Never persist when binding inside of a read attribute for validation.
#1358 Fixed type error on many to many synchronization when inverse_of is set to nil.
#1356 $in criteria can now be chained to non-complex criteria on the same key without error.
#1350, #1351 Fixed errors in the string conversions of double quotes and tilde when parameterizing keys.
#1349 Mongoid documents should not blow up when including Enumerable. (Jonas Nicklas)

2.2.3

#1295 Fixed having multiple includes only execute the eager loading of the first.
#1225 Fixed delayed persistence of embedded documents via $set.
#1002 Fix BSON object id conversion to check if legal first.

2.2.2

This release removes the restriction of a dependency on 1.3.x of the mongo ruby driver. Users may now use 1.3.x through 1.4.x.

2.2.1

Resolved Issues

#1210, #517 Allow embedded document relation queries to use dot notation. (Scott Ellard)
#1198 Enumerable target should use criteria count if loaded has no docs.
#1164 Get rid of remaining no method in_memory errors.
#1070 Allow custom field serializers to have their own constructors.
#1176 Allow access to parent documents from embedded docs in after_destroy callbacks.
#1191 Context group methods (min, max, sum) no longer return NaN but instead return nil if field doesn't exist or have values.
#1193, #1271 Always return Integers for integer fields with .000 precisions, not floats.
#1199 Fixed performance issues of hash and array field access when reading multiple times.
#1218 Fixed issues with relations referencing models with integer foreign keys.
#1219 Fixed various conflicting modifications issues when pushing and pulling from the same embedded document in a single call.
#1220 Metadata should not get overwritten by nil on binding.
#1231 Renamed Mongoid's atomic set class to Sets to avoid conflicts with Ruby's native Set after document inclusion.
#1232 Fix access to related models during before_destroy callbacks when cascading.
#1234 Fixed HABTM foreign key synchronization issues when destroying documents.
#1243 Polymorphic relations dont convert to object ids when querying if the ids are defined as strings.
#1247 Force Model.first to sort by ascending id to guarantee first document.
#1248 Added #unscoped to embedded many relations.
#1249 Destroy flags in nested attributes now actually destroy the document for has_many instead of just breaking the relation.
#1272 Don't modify configuration options in place when creating replica set connections.

2.2.0

New Features

Mongoid now contains eager loading in the form of Criteria#includes(*args). This works on has_one, has_many, belongs_to associations and requires the identity map to be enabled in order to function. Set identity_map_enabled: true in your mongoid.yml. Ex: Person.where(title: "Sir").includes(:posts, :game)
Relations can now take a module as a value to the :extend option. (Roman Shterenzon)
Capped collections can be created by passing the options to the #store_in macro: Person.store_in :people, capped: true, max: 1000000
Mongoid::Collection now supports collection.find_and_modify
Document#has_attribute? now aliases to Document#attribute_present?
#930 You can now turn off the Mongoid logger via the mongoid.yml by doing logger: false
#909 We now raise a ::Mongoid::Errors::Callback exception if persisting with a bang method and a callback returns false, instead of the uninformative validations error from before.

Major Changes

#1173 has_many relations no longer delete all documents on a set of the relation (= [ doc_one, doc_two ]) but look to the dependent option to determine what behavior should occur. :delete and :destroy will behave as before, :nullify and no option specified will both nullify the old documents without deleting.
#1142, #767 Embedded relations no longer immediately persist atomically when accessed via a parent attributes set. This includes nested attributes setting and attributes= or write_attributes. The child changes then remain dirty and atomically update when save is called on them or the parent document.

Resolved Issues

#1190 Fixed the gemspec errors due to changing README and CHANGELOG to markdown.
#1180, #1084, #955 Mongoid now checks the field types rather than if the name contains /id/ when trying to convert to object ids on criteria.
#1176 Enumerable targets should always return the in memory documents first, when calling #first
#1175 Make sure both sides of many to many relations are in sync during a create.
#1172 Referenced enumerable relations now properly handle #to_json (Daniel Doubrovkine)
#1040 Increased performance of class load times by removing all delegate calls to self.class.

2.1.9

Resolved Issues

#1159 Fixed build blocks not to cancel out each other when nested.
#1154 Don't delete many-to-many documents on empty array set.
#1153 Retain parent document reference in after callbacks.
#1151 Fix associated validation infinite loop on self referencing documents.
#1150 Validates associated on belongs_to is false by default.
#1149 Fixed metadata setting on belongs_to relations.
#1145 Metadata inverse should return nil if inverse_of was set as nil.
#1139 Enumerable targets now quack like arrays.
#1136 Setting belongs_to parent to nil no longer deletes the parent.
#1120 Don't call in_memory on relations if they don't respond to it.
#1075 Set self in default procs to the document instance.
#1072 Writing attributes for nested documents can take a hash or array of hashes.
#990 Embedded documents can use a single embedded_in with multiple parent definitions.

2.1.8

Resolved Issues

#1148 Fixed respond_to? on all relations to return properly.
#1146 Added back the Mongoid destructive fields check when defining fields.
#1141 Fixed conversions of nil values in criteria.
#1131 Verified Mongoid/Kaminari paginating correctly.
#1105 Fixed atomic update consumer to be scoped to class.
#1075 self in default lambdas and procs now references the document instance.
#740 Removed embedded_object_id configuration parameter.
#661 Fixed metadata caching on embedded documents.
#595 Fixed relation reload flagging.
#410 Moving documents from one relation to another now works as expected.

2.1.7

This was a specific release to fix MRI 1.8.7 breakages introduced by 2.1.6.

2.1.6

Resolved Issues

#1126 Fix setting of relations with other relation proxies.
#1122 Hash and array fields now properly flag as dirty on access and change.
#656 Fixed reload breaking relations on unsetting of already loaded associations.
#647 Prefer #unset to #remove_attribute for removing values.
#290 Verify pushes into deeply embedded documents.

2.1.5

Resolved Issues

#1116 Embedded children retain reference to parent in destroy callbacks.
#1110, #1115 Don't memoize metadata related helpers on documents.
#1112 db:create_indexes no longer indexes subclasses multiple times.
#1111, #1098 Don't set _id in $set operations.
#1007 Update attribute properly tracks array changes.

2.1.4

This was a specific release to get a Psych generated gemspec so no more parse errors would occur on those rubies that were using the new YAML parser.

2.1.3

Resolved Issues

#1109 Fixed validations not loading one to ones into memory.
#1107 Mongoid no longer wants required mongoid/railtie in application.rb.
#1102 Fixed nested attributes deletion.
#1097 Reload now runs after_initialize callbacks.
#1079 Embeds many no longer duplicates documents.
#1078 Fixed array criteria matching on embedded documents.
#1028 Implement scoped on one-to-many and many-to-many relations.
#988 Many-to-many clear no longer deletes the child documents.
#977 Autosaving relations works also through nested attributes.
#972 Recursive embedding now handles namespacing on generated names.
#943 Don't override Document#attributes.
#893 Verify count is not caching on many to many relations.
#815 Verify after_initialize is run in the correct place.
#793 Verify any_of scopes chain properly with any other scope.
#776 Fixed mongoid case quality when dealing with subclasses.
#747 Fixed complex criteria using its keys to render its string value.
#721 #safely now properly raises validation errors when they occur.

2.1.2

Resolved Issues

#1082 Alias size and length to count on criteria. (Adam Greene)
#1044 When multiple relations are defined for the same class, always return the default inverse first if inverse_of is not defined.
#710 Nested attributes accept both id and _id in hashes or arrays.
#1047 Ignore nil values passed to embeds_man pushes and substitution. (Derick Bailey)

2.1.1

Resolved Issues

#1021, #719 Many to many relations dont trigger extra database queries when pushing new documents.
#607 Calling create on large associations does not load the entire relation.
#1064 Mongoid::Paranoia should respect unscoped and scoped.
#1026 model#update_attribute now can update booleans to false.
#618 Crack XML library breaks Mongoid by adding #attributes method to the String class. (Stephen McGinty)

2.1.0

Major Changes

Mongoid now requires MongoDB 1.8.x in order to properly support the #bit and #rename atomic operations.
Traditional slave support has been removed from Mongoid. Replica sets should be used in place of traditional master and slave setups.
Custom field serialization has changed. Please see serializable for changes.
The dirty attribute tracking has been switched to use ActiveModel, this brings many bug fixes and changes:
#756 After callbacks and observers see what was changed instead of changes just made being in previous_changes
#434 Documents now are flagged as dirty when brand new or the state on instantiation differs from the database state. This is consistent with ActiveRecord.
#323 Mongoid now supports [field]_will_change! from ActiveModel::Dirty
Mongoid model preloading in development mode now defaults to false.
:autosave => true on relational associations now saves on update as well as create.
Mongoid now has an identity map for simple find_by_id queries. See the website for documentation.

New Features

#1067 Fields now accept a :versioned attribute to be able to disable what fields are versioned with Mongoid::Versioning. (Jim Benton)
#587 Added order preference to many and many to many associations. (Gregory Man)
Added ability to chain order_by statements. (Gregory Man)
#961 Allow arbitrary Mongo::Connection options to pass through Mongoid::Config::Database object. (Morgan Nelson)
Enable autosave for many to many references. (Dave Krupinski)
The following explicit atomic operations have been added: Model#bit, Model#pop, Model#pull, Model#push_all, Model#rename, Model#unset.
Added exception translations for Hindi. (Sukeerthi Adiga)

Resolved Issues

#974 Fix attribute_present? to work correctly then attribute value is false, thanks to @nickhoffman. (Gregory Man)
#960 create indexes rake task is not recognizing a lot of mongoid models because it has problems guessing their model names from filenames. (Tobias Schlottke)
#874 Deleting from a M-M reference is one-sided. (nickhoffman, davekrupinski)
Replace deprecated class_inheritable_hash dropped in Rails 3.1+. (Konstantin Shabanov)
Fix inconsistent state when replacing an entire many to many relation.
Don't clobber inheritable attributes when adding subclass field inheritance. (Dave Krupinski)
#914 Querying embedded documents with $or selector. (Max Golovnia)
#514 Fix marshaling of documents with relation extensions. (Chris Griego)
Metadata#extension now returns a Module, instead of a Proc, when an extension is defined.
#837 When allow_dynamic_fields is set to false and loading an embedded document with an unrecognized field, an exception is raised.
#963 Initializing array of embedded documents via hash regressed (Chris Griego, Morgan Nelson)
Mongoid::Config.reset resets the options to their default values.
Mongoid::Fields.defaults is memoized for faster instantiation of models.