README.md
# Dynamoid
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Dynamoid is an ORM for Amazon's DynamoDB for Ruby applications. It
provides similar functionality to ActiveRecord and improves on Amazon's
existing
[HashModel](http://docs.amazonwebservices.com/AWSRubySDK/latest/AWS/Record/HashModel.html)
by providing better searching tools and native association support.
DynamoDB is not like other document-based databases you might know, and
is very different indeed from relational databases. It sacrifices
anything beyond the simplest relational queries and transactional
support to provide a fast, cost-efficient, and highly durable storage
solution. If your database requires complicated relational queries and
transaction support, then this modest Gem cannot provide them for you,
and neither can DynamoDB. In those cases you would do better to look
elsewhere for your database needs.
But if you want a fast, scalable, simple, easy-to-use database (and a
Gem that supports it) then look no further!
## Installation
Installing Dynamoid is pretty simple. First include the Gem in your
Gemfile:
```ruby
gem 'dynamoid'
```
## Prerequisites
Dynamoid depends on the aws-sdk, and this is tested on the current
version of aws-sdk (~> 3), rails (>= 4). Hence the configuration as
needed for aws to work will be dealt with by aws setup.
### AWS SDK Version Compatibility
Make sure you are using the version for the right AWS SDK.
| Dynamoid version | AWS SDK Version |
| ---------------- | --------------- |
| 0.x | 1.x |
| 1.x | 2.x |
| 2.x | 2.x |
| 3.x | 3.x |
### AWS Configuration
Configure AWS access:
[Reference](https://github.com/aws/aws-sdk-ruby)
For example, to configure AWS access:
Create `config/initializers/aws.rb` as follows:
```ruby
Aws.config.update(
region: 'us-west-2',
credentials: Aws::Credentials.new('REPLACE_WITH_ACCESS_KEY_ID', 'REPLACE_WITH_SECRET_ACCESS_KEY'),
)
```
Alternatively, if you don't want Aws connection settings to be
overwritten for you entire project, you can specify connection settings
for Dynamoid only, by setting those in the `Dynamoid.configure` clause:
```ruby
require 'dynamoid'
Dynamoid.configure do |config|
config.access_key = 'REPLACE_WITH_ACCESS_KEY_ID'
config.secret_key = 'REPLACE_WITH_SECRET_ACCESS_KEY'
config.region = 'us-west-2'
end
```
Additionally, if you would like to pass in pre-configured AWS credentials
(e.g. you have an IAM role credential, you configure your credentials
elsewhere in your project, etc.), you may do so:
```ruby
require 'dynamoid'
credentials = Aws::AssumeRoleCredentials.new(
region: region,
access_key_id: key,
secret_access_key: secret,
role_arn: role_arn,
role_session_name: 'our-session'
)
Dynamoid.configure do |config|
config.region = 'us-west-2',
config.credentials = credentials
end
```
For a full list of the DDB regions, you can go
[here](http://docs.aws.amazon.com/general/latest/gr/rande.html#ddb_region).
Then you need to initialize Dynamoid config to get it going. Put code
similar to this somewhere (a Rails initializer would be a great place
for this if you're using Rails):
```ruby
require 'dynamoid'
Dynamoid.configure do |config|
# To namespace tables created by Dynamoid from other tables you might have.
# Set to nil to avoid namespacing.
config.namespace = 'dynamoid_app_development'
# [Optional]. If provided, it communicates with the DB listening at the endpoint.
# This is useful for testing with [DynamoDB Local] (http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Tools.DynamoDBLocal.html).
config.endpoint = 'http://localhost:3000'
end
```
### Ruby & Rails Compatibility
Dynamoid supports Ruby >= 2.3 and Rails >= 4.2.
Its compatibility is tested against following Ruby versions: 2.3, 2.4,
2.5, 2.6, 2.7, 3.0, 3.1, 3.2 and 3.3, JRuby 9.4.x and against Rails versions: 4.2, 5.0, 5.1,
5.2, 6.0, 6.1, 7.0 and 7.1.
## Setup
You *must* include `Dynamoid::Document` in every Dynamoid model.
```ruby
class User
include Dynamoid::Document
# fields declaration
end
```
### Table
Dynamoid has some sensible defaults for you when you create a new table,
including the table name and the primary key column. But you can change
those if you like on table creation.
```ruby
class User
include Dynamoid::Document
table name: :awesome_users, key: :user_id, read_capacity: 5, write_capacity: 5
end
```
These fields will not change an existing table: so specifying a new
read_capacity and write_capacity here only works correctly for entirely
new tables. Similarly, while Dynamoid will look for a table named
`awesome_users` in your namespace, it won't change any existing tables
to use that name; and if it does find a table with the correct name, it
won't change its hash key, which it expects will be `user_id`. If this
table doesn't exist yet, however, Dynamoid will create it with these
options.
There is a basic support of DynamoDB's [Time To Live (TTL)
mechanism](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/TTL.html).
If you declare a field as TTL field - it will be initialised if doesn't
have value yet. Default value is current time + specified seconds.
```ruby
class User
include Dynamoid::Document
table expires: { field: :ttl, after: 60 }
field :ttl, :integer
end
```
Field used to store expiration time (e.g. `ttl`) should be declared
explicitly and should have numeric type (`integer`, `number`) only.
`datetime` type is also possible but only if it's stored as number
(there is a way to store time as a string also).
It's also possible to override a global option `Dynamoid::Config.timestamps`
on a table level:
```ruby
table timestamps: false
```
This option controls generation of timestamp fields
`created_at`/`updated_at`.
It's also possible to override table capacity mode configured globally
with table level option `capacity_mode`. Valid values are
`:provisioned`, `:on_demand` and `nil`:
```ruby
table capacity_mode: :on_demand
```
If table capacity mode is on-demand, another related table-level options
`read_capacity` and `write_capacity` will be ignored.
### Fields
You'll have to define all the fields on the model and the data type of
each field. Every field on the object must be included here; if you miss
any they'll be completely bypassed during DynamoDB's initialization and
will not appear on the model objects.
By default, fields are assumed to be of type `string`. Other built-in
types are `integer`, `number`, `set`, `array`, `map`, `datetime`,
`date`, `boolean`, `binary`, `raw` and `serialized`. `array` and
`map` match List and Map DynamoDB types respectively. `raw` type means
you can store Ruby Array, Hash, String and numbers. If built-in types do
not suit you, you can use a custom field type represented by an
arbitrary class, provided that the class supports a compatible
serialization interface. The primary use case for using a custom field
type is to represent your business logic with high-level types, while
ensuring portability or backward-compatibility of the serialized
representation.
#### Note on boolean type
The boolean fields are stored as DynamoDB boolean values by default.
Dynamoid can store boolean values as strings as well - `'t'` and `'f'`.
So if you want to change the default format of boolean field you can
easily achieve this with `store_as_native_boolean` field option:
```ruby
class Document
include Dynamoid::Document
field :active, :boolean, store_as_native_boolean: false
end
```
#### Note on date type
By default date fields are persisted as days count since 1 January 1970
like UNIX time. If you prefer dates to be stored as ISO-8601 formatted
strings instead then set `store_as_string` to `true`
```ruby
class Document
include Dynamoid::Document
field :sent_on, :date, store_as_string: true
end
```
#### Note on datetime type
By default datetime fields are persisted as UNIX timestamps with
millisecond precision in DynamoDB. If you prefer datetimes to be stored
as ISO-8601 formatted strings instead then set `store_as_string` to
`true`
```ruby
class Document
include Dynamoid::Document
field :sent_at, :datetime, store_as_string: true
end
```
**WARNING:** Fields in numeric format are stored with nanoseconds as a
fraction part and precision could be lost. That's why `datetime` field
in numeric format shouldn't be used as a range key.
You have two options if you need to use a `datetime` field as a range
key:
* string format
* store `datetime` values without milliseconds (e.g. cut
them manually with `change` method - `Time.now.change(usec: 0)`
#### Note on set type
`Dynamoid`'s type `set` is stored as DynamoDB's Set attribute type.
DynamoDB supports only Set of strings, numbers and binary. Moreover Set
*must* contain elements of the same type only.
In order to use some other `Dynamoid`'s types you can specify `of`
option to declare the type of set elements.
As a result of that DynamoDB limitation, in Dynamoid only the following
scalar types are supported (note: does not support `boolean`):
`integer`, `number`, `date`, `datetime`, `serializable` and custom
types.
```ruby
class Document
include Dynamoid::Document
field :tags, :set, of: :integer
end
```
It's possible to specify field options like `store_as_string` for
`datetime` field or `serializer` for `serializable` field for `set`
elements type:
```ruby
class Document
include Dynamoid::Document
field :values, :set, of: { serialized: { serializer: JSON } }
field :dates, :set, of: { date: { store_as_string: true } }
field :datetimes, :set, of: { datetime: { store_as_string: false } }
end
```
DynamoDB doesn't allow empty strings in fields configured as `set`.
Abiding by this restriction, when `Dynamoid` saves a document it removes
all empty strings in set fields.
#### Note on array type
`Dynamoid`'s type `array` is stored as DynamoDB's List attribute type.
It can contain elements of different types (in contrast to Set attribute
type).
If you need to store in array field elements of `datetime`, `date`,
`serializable` or some custom type, which DynamoDB doesn't support
natively, you should specify element type with `of` option:
```ruby
class Document
include Dynamoid::Document
field :dates, :array, of: :date
end
```
#### Magic Columns
You get magic columns of `id` (`string`), `created_at` (`datetime`), and
`updated_at` (`datetime`) for free.
```ruby
class User
include Dynamoid::Document
field :name
field :email
field :rank, :integer
field :number, :number
field :joined_at, :datetime
field :hash, :serialized
end
```
#### Default Values
You can optionally set a default value on a field using either a plain
value or a lambda:
```ruby
field :actions_taken, :integer, default: 0
field :joined_at, :datetime, default: -> { Time.now }
```
#### Aliases
It might be helpful to define an alias for already existing field when
naming convention used for a table differs from conventions common in
Ruby:
```ruby
field firstName, :string, alias: :first_name
```
This way there will be generated
setters/getters/`<name>?`/`<name>_before_type_cast` methods for both
original field name (`firstName`) and an alias (`first_name`).
```ruby
user = User.new(first_name: 'Michael')
user.first_name # => 'Michael'
user.firstName # => 'Michael'
```
#### Custom Types
To use a custom type for a field, suppose you have a `Money` type.
```ruby
class Money
# ... your business logic ...
def dynamoid_dump
'serialized representation as a string'
end
def self.dynamoid_load(_serialized_str)
# parse serialized representation and return a Money instance
Money.new(1.23)
end
end
class User
include Dynamoid::Document
field :balance, Money
end
```
If you want to use a third-party class (which does not support
`#dynamoid_dump` and `.dynamoid_load`) as your field type, you can use
an adapter class providing `.dynamoid_dump` and `.dynamoid_load` class
methods for your third-party class. `.dynamoid_load` can remain the same
from the previous example; here we just add a level of indirection for
serializing. Example:
```ruby
# Third-party Money class
class Money; end
class MoneyAdapter
def self.dynamoid_load(_money_serialized_str)
Money.new(1.23)
end
def self.dynamoid_dump(money_obj)
money_obj.value.to_s
end
end
class User
include Dynamoid::Document
field :balance, MoneyAdapter
end
```
Lastly, you can control the data type of your custom-class-backed field
at the DynamoDB level. This is especially important if you want to use
your custom field as a numeric range or for number-oriented queries. By
default custom fields are persisted as a string attribute, but your
custom class can override this with a `.dynamoid_field_type` class
method, which would return either `:string` or `:number`.
DynamoDB may support some other attribute types that are not yet
supported by Dynamoid.
### Sort key
Along with partition key table may have a sort key. In order to declare
it in a model `range` class method should be used:
```ruby
class Post
include Dynamoid::Document
range :posted_at, :datetime
end
```
Second argument, type, is optional. Default type is `string`.
### Associations
Just like in ActiveRecord (or your other favorite ORM), Dynamoid uses
associations to create links between models.
**WARNING:** Associations are not supported for models with compound
primary key. If a model declares a range key it should not declare any
association itself and be referenced by an association in another model.
The only supported associations (so far) are `has_many`, `has_one`,
`has_and_belongs_to_many`, and `belongs_to`. Associations are very
simple to create: just specify the type, the name, and then any options
you'd like to pass to the association. If there's an inverse association
either inferred or specified directly, Dynamoid will update both objects
to point at each other.
```ruby
class User
include Dynamoid::Document
# ...
has_many :addresses
has_many :students, class: User
belongs_to :teacher, class_name: :user
belongs_to :group
belongs_to :group, foreign_key: :group_id
has_one :role
has_and_belongs_to_many :friends, inverse_of: :friending_users
end
class Address
include Dynamoid::Document
# ...
belongs_to :user # Automatically links up with the user model
end
```
Contrary to what you'd expect, association information is always
contained on the object specifying the association, even if it seems
like the association has a foreign key. This is a side effect of
DynamoDB's structure: it's very difficult to find foreign keys without
an index. Usually you won't find this to be a problem, but it does mean
that association methods that build new models will not work correctly -
for example, `user.addresses.new` returns an address that is not
associated to the user. We'll be correcting this ~soon~ maybe someday,
if we get a pull request.
### Validations
Dynamoid bakes in ActiveModel validations, just like ActiveRecord does.
```ruby
class User
include Dynamoid::Document
# ...
validates_presence_of :name
validates_format_of :email, with: /@/
end
```
To see more usage and examples of ActiveModel validations, check out the
[ActiveModel validation
documentation](http://api.rubyonrails.org/classes/ActiveModel/Validations.html).
If you want to bypass model validation, pass `validate: false` to `save`
call:
```ruby
model.save(validate: false)
```
### Callbacks
Dynamoid also employs ActiveModel callbacks. Right now the following
callbacks are supported:
- `save` (before, after, around)
- `create` (before, after, around)
- `update` (before, after, around)
- `validation` (before, after)
- `destroy` (before, after, around)
- `after_touch`
- `after_initialize`
- `after_find`
Example:
```ruby
class User
include Dynamoid::Document
# ...
before_save :set_default_password
after_create :notify_friends
after_destroy :delete_addresses
end
```
### STI
Dynamoid supports STI (Single Table Inheritance) like Active Record
does. You need just specify `type` field in a base class. Example:
```ruby
class Animal
include Dynamoid::Document
field :name
field :type
end
class Cat < Animal
field :lives, :integer
end
cat = Cat.create(name: 'Morgan')
animal = Animal.find(cat.id)
animal.class
#=> Cat
```
If you already have DynamoDB tables and `type` field already exists and
has its own semantic it leads to conflict. It's possible to tell
Dynamoid to use another field (even not existing) instead of `type` one
with `inheritance_field` table option:
```ruby
class Car
include Dynamoid::Document
table inheritance_field: :my_new_type
field :my_new_type
end
c = Car.create
c.my_new_type
#=> "Car"
```
### Type casting
Dynamoid supports type casting and tries to do it in the most convenient
way. Values for all fields (except custom type) are coerced to declared
field types.
Some obvious rules are used, e.g.:
for boolean field:
```ruby
document.boolean_field = 'off'
# => false
document.boolean_field = 'false'
# => false
document.boolean_field = 'some string'
# => true
```
or for integer field:
```ruby
document.integer_field = 42.3
# => 42
document.integer_field = '42.3'
# => 42
document.integer_field = true
# => 1
```
If time zone isn't specified for `datetime` value - application time
zone is used.
To access field value before type casting following method could be
used: `attributes_before_type_cast` and
`read_attribute_before_type_cast`.
There is `<name>_before_type_cast` method for every field in a model as
well.
### Dirty API
Dynamoid supports Dirty API which is equivalent to [Rails 5.2
`ActiveModel::Dirty`](https://api.rubyonrails.org/v5.2/classes/ActiveModel/Dirty.html).
There is only one limitation - change in place of field isn't detected
automatically.
## Usage
### Object Creation
Dynamoid's syntax is generally very similar to ActiveRecord's. Making
new objects is simple:
```ruby
u = User.new(name: 'Josh')
u.email = 'josh@joshsymonds.com'
u.save
```
Save forces persistence to the data store: a unique ID is also assigned,
but it is a string and not an auto-incrementing number.
```ruby
u.id # => '3a9f7216-4726-4aea-9fbc-8554ae9292cb'
```
To use associations, you use association methods very similar to
ActiveRecord's:
```ruby
address = u.addresses.create
address.city = 'Chicago'
address.save
```
To create multiple documents at once:
```ruby
User.create([{ name: 'Josh' }, { name: 'Nick' }])
```
There is an efficient and low-level way to create multiple documents
(without validation and callbacks running):
```ruby
users = User.import([{ name: 'Josh' }, { name: 'Nick' }])
```
### Querying
Querying can be done in one of three ways:
```ruby
Address.find(address.id) # Find directly by ID.
Address.where(city: 'Chicago').all # Find by any number of matching criteria...
# Though presently only "where" is supported.
Address.find_by_city('Chicago') # The same as above, but using ActiveRecord's older syntax.
```
And you can also query on associations:
```ruby
u.addresses.where(city: 'Chicago').all
```
But keep in mind Dynamoid - and document-based storage systems in
general - are not drop-in replacements for existing relational
databases. The above query does not efficiently perform a conditional
join, but instead finds all the user's addresses and naively filters
them in Ruby. For large associations this is a performance hit compared
to relational database engines.
**Warning:** There is a caveat with filtering documents by `nil` value
attribute. By default Dynamoid ignores attributes with `nil` value and
doesn't store them in a DynamoDB document. This behavior could be
changed with `store_attribute_with_nil_value` config option.
If Dynamoid ignores `nil` value attributes `null`/`not_null` operators
should be used in query:
```ruby
Address.where('postcode.null': true)
Address.where('postcode.not_null': true)
```
If Dynamoid keeps `nil` value attributes `eq`/`ne` operators should be
used instead:
```ruby
Address.where(postcode: nil)
Address.where('postcode.ne': nil)
```
#### Limits
There are three types of limits that you can query with:
1. `record_limit` - The number of evaluated records that are returned by
the query.
2. `scan_limit` - The number of scanned records that DynamoDB will look
at before returning.
3. `batch_size` - The number of records requested to DynamoDB per
underlying request, good for large queries!
Using these in various combinations results in the underlying requests
to be made in the smallest size possible and the query returns once
`record_limit` or `scan_limit` is satisfied. It will attempt to batch
whenever possible.
You can thus limit the number of evaluated records, or select a record
from which to start in order to support pagination.
```ruby
Address.record_limit(5).start(address) # Only 5 addresses starting at `address`
```
Where `address` is an instance of the model or a hash
`{the_model_hash_key: 'value', the_model_range_key: 'value'}`. Keep in
mind that if you are passing a hash to `.start()` you need to explicitly
define all required keys in it including range keys, depending on table
or secondary indexes signatures, otherwise you'll get an
`Aws::DynamoDB::Errors::ValidationException` either for `Exclusive Start
Key must have same size as table's key schema` or `The provided starting
key is invalid`
If you are potentially running over a large data set and this is
especially true when using certain filters, you may want to consider
limiting the number of scanned records (the number of records DynamoDB
infrastructure looks through when evaluating data to return):
```ruby
Address.scan_limit(5).start(address) # Only scan at most 5 records and return what's found starting from `address`
```
For large queries that return many rows, Dynamoid can use AWS' support
for requesting documents in batches:
```ruby
# Do some maintenance on the entire table without flooding DynamoDB
Address.batch(100).each { |addr| addr.do_some_work && sleep(0.01) }
Address.record_limit(10_000).batch(100).each { |addr| addr.do_some_work && sleep(0.01) } # Batch specified as part of a chain
```
The implication of batches is that the underlying requests are done in
the batch sizes to make the request and responses more manageable. Note
that this batching is for `Query` and `Scans` and not `BatchGetItem`
commands.
#### DynamoDB pagination
At times it can be useful to rely on DynamoDB [low-level
pagination](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Query.html#Query.Pagination)
instead of fixed pages sizes. Each page results in a single Query or
Scan call to DynamoDB, but returns an unknown number of records.
Access to the native DynamoDB pages can be obtained via the
`find_by_pages` method, which yields arrays of records.
```ruby
Address.find_by_pages do |addresses, metadata|
end
```
Each yielded pages returns page metadata as the second argument, which
is a hash including a key `:last_evaluated_key`. The value of this key
can be used for the `start` method to fetch the next page of records.
This way it can be used for instance to implement efficiently pagination
in web-applications:
```ruby
class UserController < ApplicationController
def index
next_page = params[:next_page_token] ? JSON.parse(Base64.decode64(params[:next_page_token])) : nil
records, metadata = User.start(next_page).find_by_pages.first
render json: {
records: records,
next_page_token: Base64.encode64(metadata[:last_evaluated_key].to_json)
}
end
end
```
#### Sort Conditions and Filters
You are able to optimize query with condition for sort key. Following
operators are available: `gt`, `lt`, `gte`, `lte`, `begins_with`,
`between` as well as equality:
```ruby
Address.where(latitude: 10_212)
Address.where('latitude.gt': 10_212)
Address.where('latitude.lt': 10_212)
Address.where('latitude.gte': 10_212)
Address.where('latitude.lte': 10_212)
Address.where('city.begins_with': 'Lon')
Address.where('latitude.between': [10_212, 20_000])
```
You are able to filter results on the DynamoDB side and specify
conditions for non-key fields. Following additional operators are
available: `in`, `contains`, `not_contains`, `null`, `not_null`:
```ruby
Address.where('city.in': %w[London Edenburg Birmingham])
Address.where('city.contains': ['on'])
Address.where('city.not_contains': ['ing'])
Address.where('postcode.null': false)
Address.where('postcode.not_null': true)
```
**WARNING:** Please take into account that `NULL` and `NOT_NULL`
operators check attribute presence in a document, not value. So if
attribute `postcode`'s value is `NULL`, `NULL` operator will return
false because attribute exists even if has `NULL` value.
#### Selecting some specific fields only
It could be done with `project` method:
```ruby
class User
include Dynamoid::Document
field :name
end
User.create(name: 'Alex')
user = User.project(:name).first
user.id # => nil
user.name # => 'Alex'
user.created_at # => nil
```
Returned models with have filled specified fields only.
Several fields could be specified:
```ruby
user = User.project(:name, :created_at)
```
### Consistent Reads
Querying supports consistent reading. By default, DynamoDB reads are
eventually consistent: if you do a write and then a read immediately
afterwards, the results of the previous write may not be reflected. If
you need to do a consistent read (that is, you need to read the results
of a write immediately) you can do so, but keep in mind that consistent
reads are twice as expensive as regular reads for DynamoDB.
```ruby
Address.find(address.id, consistent_read: true) # Find an address, ensure the read is consistent.
Address.where(city: 'Chicago').consistent.all # Find all addresses where the city is Chicago, with a consistent read.
```
### Range Finding
If you have a range index, Dynamoid provides a number of additional
other convenience methods to make your life a little easier:
```ruby
User.where('created_at.gt': DateTime.now - 1.day).all
User.where('created_at.lt': DateTime.now - 1.day).all
```
It also supports `gte` and `lte`. Turning those into symbols and
allowing a Rails SQL-style string syntax is in the works. You can only
have one range argument per query, because of DynamoDB inherent
limitations, so use it sensibly!
### Updating
In order to update document you can use high level methods
`#update_attributes`, `#update_attribute` and `.update`. They run
validation and callbacks.
```ruby
Address.find(id).update_attributes(city: 'Chicago')
Address.find(id).update_attribute(:city, 'Chicago')
Address.update(id, city: 'Chicago')
```
There are also some low level methods `#update`, `.update_fields` and
`.upsert`. They don't run validation and callbacks (except `#update` -
it runs `update` callbacks). All of them support conditional updates.
`#upsert` will create new document if document with specified `id`
doesn't exist.
```ruby
Address.find(id).update do |i|
i.set city: 'Chicago'
i.add latitude: 100
i.delete set_of_numbers: 10
end
Address.find(id).update(if: { deliverable: true }) do |i|
i.set city: 'Chicago'
end
Address.update_fields(id, city: 'Chicago')
Address.update_fields(id, { city: 'Chicago' }, if: { deliverable: true })
Address.upsert(id, city: 'Chicago')
Address.upsert(id, { city: 'Chicago' }, if: { deliverable: true })
```
By default, `#upsert` will update all attributes of the document if it already exists.
To idempotently create-but-not-update a record, apply the `unless_exists` condition
to its keys when you upsert.
```ruby
Address.upsert(id, { city: 'Chicago' }, { unless_exists: [:id] })
```
### Deleting
In order to delete some items `delete_all` method should be used. Any
callback won't be called. Items delete in efficient way in batch.
```ruby
Address.where(city: 'London').delete_all
```
### Global Secondary Indexes
You can define index with `global_secondary_index`:
```ruby
class User
include Dynamoid::Document
field :name
field :age, :number
global_secondary_index hash_key: :age # Must come after field definitions.
end
```
There are the following options:
* `hash_key` - is used as hash key of an index,
* `range_key` - is used as range key of an index,
* `projected_attributes` - list of fields to store in an index or has a
predefined value `:keys_only`, `:all`; `:keys_only` is a default,
* `name` - an index will be created with this name when a table is
created; by default name is generated and contains table name and keys
names,
* `read_capacity` - is used when table created and used as an index
capacity; by default equals `Dynamoid::Config.read_capacity`,
* `write_capacity` - is used when table created and used as an index
capacity; by default equals `Dynamoid::Config.write_capacity`
The only mandatory option is `name`.
**WARNING:** In order to use global secondary index in `Document.where`
implicitly you need to have all the attributes of the original table in
the index and declare it with option `projected_attributes: :all`:
```ruby
class User
# ...
global_secondary_index hash_key: :age, projected_attributes: :all
end
```
There is only one implicit way to query Global and Local Secondary
Indexes (GSI/LSI).
#### Implicit
The second way implicitly uses your GSI through the `where` clauses and
deduces the index based on the query fields provided. Another added
benefit is that it is built into query chaining so you can use all the
methods used in normal querying. The explicit way from above would be
rewritten as follows:
```ruby
where(dynamo_primary_key_column_name => dynamo_primary_key_value,
"#{range_column}.#{range_modifier}" => range_value)
.scan_index_forward(false)
```
The only caveat with this method is that because it is also used for
general querying, it WILL NOT use a GSI unless it explicitly has defined
`projected_attributes: :all` on the GSI in your model. This is because
GSIs that do not have all attributes projected will only contain the
index keys and therefore will not return objects with fully resolved
field values. It currently opts to provide the complete results rather
than partial results unless you've explicitly looked up the data.
*Future TODO could involve implementing `select` in chaining as well as
resolving the fields with a second query against the table since a query
against GSI then a query on base table is still likely faster than scan
on the base table*
### Transaction Writes
Multiple write actions can be grouped together and submitted as an all-or-nothing operation.
See the [transation documentation](README_transact.md).
### PartiQL
To run PartiQL statements `Dynamoid.adapter.execute` method should be
used:
```ruby
Dynamoid.adapter.execute("UPDATE users SET name = 'Mike' WHERE id = '1'")
```
Parameters are also supported:
```ruby
Dynamoid.adapter.execute('SELECT * FROM users WHERE id = ?', ['1'])
```
## Configuration
Listed below are all configuration options.
* `adapter` - useful only for the gem developers to switch to a new
adapter. Default and the only available value is `aws_sdk_v3`
* `namespace` - prefix for table names, default is
`dynamoid_#{application_name}_#{environment}` for Rails application
and `dynamoid` otherwise
* `logger` - by default it's a `Rails.logger` in Rails application and
`stdout` otherwise. You can disable logging by setting `nil` or
`false` values. Set `true` value to use defaults
* `access_key` - DynamoDb custom access key for AWS credentials, override global
AWS credentials if they're present
* `secret_key` - DynamoDb custom secret key for AWS credentials, override global
AWS credentials if they're present
* `credentials` - DynamoDb custom pre-configured credentials, override global
AWS credentials if they're present
* `region` - DynamoDb custom credentials for AWS, override global AWS
credentials if they're present
* `batch_size` - when you try to load multiple items at once with
* `batch_get_item` call Dynamoid loads them not with one api call but
piece by piece. Default is 100 items
* `capacity_mode` - used at a table creation and means whether a table
read/write capacity mode will be on-demand or provisioned. Allowed
values are `:on_demand` and `:provisioned`. Default value is `nil` which
means provisioned mode will be used.
* `read_capacity` - is used at table or indices creation. Default is 100
(units)
* `write_capacity` - is used at table or indices creation. Default is 20
(units)
* `warn_on_scan` - log warnings when scan table. Default is `true`
* `endpoint` - if provided, it communicates with the DynamoDB listening
at the endpoint. This is useful for testing with
[DynamoDB Local](http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Tools.DynamoDBLocal.html)
* `identity_map` - ensures that each object gets loaded only once by
keeping every loaded object in a map. Looks up objects using the map
when referring to them. Isn't thread safe. Default is `false`.
`Use Dynamoid::Middleware::IdentityMap` to clear identity map for each HTTP request
* `timestamps` - by default Dynamoid sets `created_at` and `updated_at`
fields at model creation and updating. You can disable this
behavior by setting `false` value
* `sync_retry_max_times` - when Dynamoid creates or deletes table
synchronously it checks for completion specified times. Default is 60
(times). It's a bit over 2 minutes by default
* `sync_retry_wait_seconds` - time to wait between retries. Default is 2
(seconds)
* `convert_big_decimal` - if `true` then Dynamoid converts numbers
stored in `Hash` in `raw` field to float. Default is `false`
* `store_attribute_with_nil_value` - if `true` Dynamoid keeps attribute
with `nil` value in a document. Otherwise Dynamoid removes it while
saving a document. Default is `nil` which equals behaviour with `false`
value.
* `models_dir` - `dynamoid:create_tables` rake task loads DynamoDb
models from this directory. Default is `./app/models`.
* `application_timezone` - Dynamoid converts all `datetime` fields to
specified time zone when loads data from the storage.
Acceptable values - `:utc`, `:local` (to use system time zone) and
time zone name e.g. `Eastern Time (US & Canada)`. Default is `utc`
* `dynamodb_timezone` - When a datetime field is stored in string format
Dynamoid converts it to specified time zone when saves a value to the
storage. Acceptable values - `:utc`, `:local` (to use system time
zone) and time zone name e.g. `Eastern Time (US & Canada)`. Default is
`utc`
* `store_datetime_as_string` - if `true` then Dynamoid stores :datetime
fields in ISO 8601 string format. Default is `false`
* `store_date_as_string` - if `true` then Dynamoid stores :date fields
in ISO 8601 string format. Default is `false`
* `store_empty_string_as_nil` - store attribute's empty String value as NULL. Default is `true`
* `store_boolean_as_native` - if `true` Dynamoid stores boolean fields
as native DynamoDB boolean values. Otherwise boolean fields are stored
as string values `'t'` and `'f'`. Default is `true`
* `backoff` - is a hash: key is a backoff strategy (symbol), value is
parameters for the strategy. Is used in batch operations. Default id
`nil`
* `backoff_strategies`: is a hash and contains all available strategies.
Default is `{ constant: ..., exponential: ...}`
* `log_formatter`: overrides default AWS SDK formatter. There are
several canned formatters: `Aws::Log::Formatter.default`,
`Aws::Log::Formatter.colored` and `Aws::Log::Formatter.short`. Please
look into `Aws::Log::Formatter` AWS SDK documentation in order to
provide own formatter.
* `http_continue_timeout`: The number of seconds to wait for a
100-continue HTTP response before sending the request body. Default
option value is `nil`. If not specified effected value is `1`
* `http_idle_timeout`: The number of seconds an HTTP connection is
allowed to sit idle before it is considered stale. Default option
value is `nil`. If not specified effected value is `5`
* `http_open_timeout`: The number of seconds to wait when opening a HTTP
session. Default option value is `nil`. If not specified effected
value is `15`
* `http_read_timeout`:The number of seconds to wait for HTTP response
data. Default option value is `nil`. If not specified effected value
is `60`
* `create_table_on_save`: if `true` then Dynamoid creates a
corresponding table in DynamoDB at model persisting if the table
doesn't exist yet. Default is `true`
## Concurrency
Dynamoid supports basic, ActiveRecord-like optimistic locking on save
operations. Simply add a `lock_version` column to your table like so:
```ruby
class MyTable
# ...
field :lock_version, :integer
# ...
end
```
In this example, all saves to `MyTable` will raise an
`Dynamoid::Errors::StaleObjectError` if a concurrent process loaded,
edited, and saved the same row. Your code should trap this exception,
reload the row (so that it will pick up the newest values), and try the
save again.
Calls to `update` and `update!` also increment the `lock_version`,
however, they do not check the existing value. This guarantees that a
update operation will raise an exception in a concurrent save operation,
however a save operation will never cause an update to fail. Thus,
`update` is useful & safe only for doing atomic operations (e.g.
increment a value, add/remove from a set, etc), but should not be used
in a read-modify-write pattern.
### Backoff strategies
You can use several methods that run efficiently in batch mode like
`.find_all` and `.import`. It affects `Query` and `Scan` operations as
well.
The backoff strategy will be used when, for any reason, some items could
not be processed as part of a batch mode command. Operations will be
re-run to process these items.
Exponential backoff is the recommended way to handle throughput limits
exceeding and throttling on the table.
There are two built-in strategies - constant delay and truncated binary
exponential backoff. By default no backoff is used but you can specify
one of the built-in ones:
```ruby
Dynamoid.configure do |config|
config.backoff = { constant: 2.second }
end
Dynamoid.configure do |config|
config.backoff = { exponential: { base_backoff: 0.2.seconds, ceiling: 10 } }
end
```
You can just specify strategy without any arguments to use default
presets:
```ruby
Dynamoid.configure do |config|
config.backoff = :constant
end
```
You can use your own strategy in the following way:
```ruby
Dynamoid.configure do |config|
config.backoff_strategies[:custom] = lambda do |n|
-> { sleep rand(n) }
end
config.backoff = { custom: 10 }
end
```
## Rake Tasks
There are a few Rake tasks available out of the box:
* `rake dynamoid:create_tables`
* `rake dynamoid:ping`
In order to use them in non-Rails application they should be required
explicitly:
```ruby
# Rakefile
Rake::Task.define_task(:environment)
require 'dynamoid/tasks'
```
The Rake tasks depend on `:environment` task so it should be declared as
well.
## Test Environment
In test environment you will most likely want to clean the database
between test runs to keep tests completely isolated. This can be
achieved like so
```ruby
module DynamoidReset
def self.all
Dynamoid.adapter.list_tables.each do |table|
# Only delete tables in our namespace
if table =~ /^#{Dynamoid::Config.namespace}/
Dynamoid.adapter.delete_table(table)
end
end
Dynamoid.adapter.tables.clear
# Recreate all tables to avoid unexpected errors
Dynamoid.included_models.each { |m| m.create_table(sync: true) }
end
end
# Reduce noise in test output
Dynamoid.logger.level = Logger::FATAL
```
If you're using RSpec you can invoke the above like so:
```ruby
RSpec.configure do |config|
config.before(:each) do
DynamoidReset.all
end
end
```
In addition, the first test for each model may fail if the relevant models are not included in `included_models`. This can be fixed by adding this line before the `DynamoidReset` module:
```ruby
Dir[File.join(Dynamoid::Config.models_dir, '**/*.rb')].sort.each { |file| require file }
```
Note that this will require _all_ models in your models folder - you can also explicitly require only certain models if you would prefer to.
In Rails, you may also want to ensure you do not delete non-test data
accidentally by adding the following to your test environment setup:
```ruby
raise "Tests should be run in 'test' environment only" if Rails.env != 'test'
Dynamoid.configure do |config|
config.namespace = "#{Rails.application.railtie_name}_#{Rails.env}"
end
```
## Logging
There is a config option `logger`. Dynamoid writes requests and
responses to DynamoDB using this logger on the `debug` level. So in
order to troubleshoot and debug issues just set it:
```ruby
class User
include Dynamoid::Document
field name
end
Dynamoid.config.logger.level = :debug
Dynamoid.config.endpoint = 'http://localhost:8000'
User.create(name: 'Alex')
# => D, [2019-05-12T20:01:07.840051 #75059] DEBUG -- : put_item | Request "{\"TableName\":\"dynamoid_users\",\"Item\":{\"created_at\":{\"N\":\"1557680467.608749\"},\"updated_at\":{\"N\":\"1557680467.608809\"},\"id\":{\"S\":\"1227eea7-2c96-4b8a-90d9-77b38eb85cd0\"}},\"Expected\":{\"id\":{\"Exists\":false}}}" | Response "{}"
# => D, [2019-05-12T20:01:07.842397 #75059] DEBUG -- : (231.28 ms) PUT ITEM - ["dynamoid_users", {:created_at=>0.1557680467608749e10, :updated_at=>0.1557680467608809e10, :id=>"1227eea7-2c96-4b8a-90d9-77b38eb85cd0", :User=>nil}, {}]
```
The first line is a body of HTTP request and response. The second line -
Dynamoid internal logging of API call (`PUT ITEM` in our case) with
timing (231.28 ms).
## Credits
Dynamoid borrows code, structure, and even its name very liberally from
the truly amazing [Mongoid](https://github.com/mongoid/mongoid). Without
Mongoid to crib from none of this would have been possible, and I hope
they don't mind me reusing their very awesome ideas to make DynamoDB
just as accessible to the Ruby world as MongoDB.
Also, without contributors the project wouldn't be nearly as awesome. So
many thanks to:
* [Chris Hobbs](https://github.com/ckhsponge)
* [Logan Bowers](https://github.com/loganb)
* [Lane LaRue](https://github.com/luxx)
* [Craig Heneveld](https://github.com/cheneveld)
* [Anantha Kumaran](https://github.com/ananthakumaran)
* [Jason Dew](https://github.com/jasondew)
* [Luis Arias](https://github.com/luisantonioa)
* [Stefan Neculai](https://github.com/stefanneculai)
* [Philip White](https://github.com/philipmw) *
* [Peeyush Kumar](https://github.com/peeyush1234)
* [Sumanth Ravipati](https://github.com/sumocoder)
* [Pascal Corpet](https://github.com/pcorpet)
* [Brian Glusman](https://github.com/bglusman) *
* [Peter Boling](https://github.com/pboling) *
* [Andrew Konchin](https://github.com/andrykonchin) *
\* Current Maintainers
## Running the tests
Running the tests is fairly simple. You should have an instance of
DynamoDB running locally. Follow these steps to setup your test
environment.
* First download and unpack the latest version of DynamoDB. We have a
script that will do this for you if you use bash, and homebrew on a Mac.
```shell
bin/setup
```
* Start the local instance of DynamoDB to listen in ***8000*** port
```shell
bin/start_dynamodblocal
```
* and lastly, use `rake` to run the tests.
```shell
rake
```
* When you are done, remember to stop the local test instance of
dynamodb
```shell
bin/stop_dynamodblocal
```
If you run into issues, please try these steps first.
NOTE: You can use any version manager: rvm, rbenv, chruby, asdf-ruby
```shell
asdf install ruby 3.1.1
asdf local ruby 3.1.1
gem update --system
bundle install
```
## Security
See [SECURITY.md][security].
## Related links
This documentation may be useful for the contributors:
- <https://docs.aws.amazon.com/sdk-for-ruby/v3/developer-guide/welcome.html>
- <https://docs.aws.amazon.com/sdk-for-ruby/v3/api/index.html>
## License
The gem is available as open source under the terms of
the [MIT License][license] [][license-ref].
See [LICENSE][license] for the official [Copyright Notice][copyright-notice-explainer].
[copyright-notice-explainer]: https://opensource.stackexchange.com/questions/5778/why-do-licenses-such-as-the-mit-license-specify-a-single-year
[license]: https://github.com/Dynamoid/dynamoid/blob/master/LICENSE.txt
[license-ref]: https://opensource.org/licenses/MIT
[security]: https://github.com/Dynamoid/dynamoid/blob/master/SECURITY.md
[⛳️gem]: https://rubygems.org/gems/dynamoid
[⛳️version-img]: http://img.shields.io/gem/v/dynamoid.svg
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[🖐gitmoji-img]: https://img.shields.io/badge/gitmoji-3.9.0-FFDD67.svg?style=flat
[🚎yard]: https://www.rubydoc.info/gems/dynamoid
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[🧮semver-img]: https://img.shields.io/badge/semver-2.0.0-FFDD67.svg?style=flat
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[🖇sponsor-img]: https://img.shields.io/opencollective/all/dynamoid
[🖇sponsor]: https://opencollective.com/dynamoid
[🖇triage-help]: https://www.codetriage.com/dynamoid/dynamoid
[🖇triage-help-img]: https://www.codetriage.com/dynamoid/dynamoid/badges/users.svg
[🏘sup-wf]: https://github.com/Dynamoid/dynamoid/actions/workflows/ci.yml?query=branch%3Amaster
[🏘sup-wf-img]: https://github.com/Dynamoid/dynamoid/actions/workflows/ci.yml/badge.svg?branch=master