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Module: ActiveRecord::Integration

Relationships & Source Files
Namespace Children
Modules:
ClassMethods
Extension / Inclusion / Inheritance Descendants
Included In:
Base
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, ::ActiveSupport::Concern
Defined in: activerecord/lib/active_record/integration.rb

Class Method Summary

::ActiveSupport::Concern - Extended

class_methods

Define class methods from given block.
included

Evaluate given block in context of base class, so that you can write class macros here.
prepended

Evaluate given block in context of base class, so that you can write class macros here.
append_features, prepend_features

Instance Method Summary

DSL Calls

included

[ GitHub ] 


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# File 'activerecord/lib/active_record/integration.rb', line 9

included do
  ##
  # :singleton-method:
  # Indicates the format used to generate the timestamp in the cache key, if
  # versioning is off. Accepts any of the symbols in Time::DATE_FORMATS.
  #
  # This is :usec, by default.
  class_attribute :cache_timestamp_format, instance_writer: false, default: :usec

  ##
  # :singleton-method:
  # Indicates whether to use a stable #cache_key method that is accompanied
  # by a changing version in the #cache_version method.
  #
  # This is true, by default on \Rails 5.2 and above.
  class_attribute :cache_versioning, instance_writer: false, default: false

  ##
  # :singleton-method:
  # Indicates whether to use a stable #cache_key method that is accompanied
  # by a changing version in the #cache_version method on collections.
  #
  # This is false, by default until \Rails 6.1.
  class_attribute :collection_cache_versioning, instance_writer: false, default: false
end

Instance Method Details

#cache_key

Returns a stable cache key that can be used to identify this record.

Product.new.cache_key     # => "products/new"
Product.find(5).cache_key # => "products/5"

If Base.cache_versioning is turned off, as it was in Rails 5.1 and earlier, the cache key will also include a version.

Product.cache_versioning = false
Product.find(5).cache_key  # => "products/5-20071224150000" (updated_at available)
[ GitHub ] 

  


# File 'activerecord/lib/active_record/integration.rb', line 72



def cache_key
  if new_record?
    "#{model_name.cache_key}/new"
  else
    if cache_version
      "#{model_name.cache_key}/#{id}"
    else
      timestamp = max_updated_column_timestamp

      if timestamp
        timestamp = timestamp.utc.to_fs(cache_timestamp_format)
        "#{model_name.cache_key}/#{id}-#{timestamp}"
      else
        "#{model_name.cache_key}/#{id}"
      end
    end
  end
end


  








  

    #cache_key_with_version  
  



  

    

Returns a cache key along with the version.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/integration.rb', line 114



def cache_key_with_version
  if version = cache_version
    "#{cache_key}-#{version}"
  else
    cache_key
  end
end


  








  

    #cache_version  
  



  

    

Returns a cache version that can be used together with the cache key to form a recyclable caching scheme. By default, the #updated_at column is used for the cache_version, but this method can be overwritten to return something else.



Note, this method will return nil if Base.cache_versioning is set to false.


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/integration.rb', line 97



def cache_version
  return unless cache_versioning

  if has_attribute?("updated_at")
    timestamp = updated_at_before_type_cast
    if can_use_fast_cache_version?(timestamp)
      raw_timestamp_to_cache_version(timestamp)

    elsif timestamp = updated_at
      timestamp.utc.to_fs(cache_timestamp_format)
    end
  elsif self.class.has_attribute?("updated_at")
    raise ActiveModel::MissingAttributeError, "missing attribute 'updated_at' for #{self.class}"
  end
end


  








  

    #can_use_fast_cache_version?(timestamp)  ⇒ Boolean  (private)
  



  

    

Detects if the value before type cast can be used to generate a cache_version.



The fast cache version only works with a string value directly from the database.



We also must check if the timestamp format has been changed or if the timezone is not set to UTC then we cannot apply our transformations correctly.


  





  


  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/integration.rb', line 178



def can_use_fast_cache_version?(timestamp)
  timestamp.is_a?(String) &&
    cache_timestamp_format == :usec &&
    # FIXME: checking out a connection for this is wasteful
    # we should store/cache this information in the schema cache
    # or similar.
    self.class.with_connection(&:default_timezone) == :utc &&
    !updated_at_came_from_user?
end


  








  

    #raw_timestamp_to_cache_version(timestamp)   (private)
  



  

    

Converts a raw database string to :usec format.



Example:



timestamp = "2018-10-15 20:02:15.266505"
raw_timestamp_to_cache_version(timestamp)
# => "20181015200215266505"



PostgreSQL truncates trailing zeros, github.com/postgres/postgres/commit/3e1beda2cde3495f41290e1ece5d544525810214 to account for this we pad the output with zeros


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/integration.rb', line 200



def raw_timestamp_to_cache_version(timestamp)
  key = timestamp.delete("- :.")
  if key.length < 20
    key.ljust(20, "0")
  else
    key
  end
end


  








  

    #to_param  
  



  

    

Returns a ::String, which Action Pack uses for constructing a URL to this object. The default implementation returns this record’s id as a ::String, or nil if this record’s unsaved.



For example, suppose that you have a User model, and that you have a resources :users route. Normally, user_path will construct a path with the user object’s ‘id’ in it:



user = User.find_by(name: 'Phusion')
user_path(user)  # => "/users/1"



You can override to_param in your model to make user_path construct a path using the user’s name instead of the user’s id:



class User < ActiveRecord::Base
  def to_param  # overridden
    name
  end
end

user = User.find_by(name: 'Phusion')
user_path(user)  # => "/users/Phusion"


  



  [ GitHub ]


  

  


# File 'activerecord/lib/active_record/integration.rb', line 57



def to_param
  return unless id
  Array(id).join(self.class.param_delimiter)
end