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# frozen_string_literal: true
require "active_support/core_ext/string/filters"
module ActiveRecord
module Integration
extend ActiveSupport::Concern
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 <tt>Time::DATE_FORMATS</tt>.
#
# 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
end
# 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
# <tt>resources :users</tt> 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"
def to_param
# We can't use alias_method here, because method 'id' optimizes itself on the fly.
id && id.to_s # Be sure to stringify the id for routes
end
# 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 ActiveRecord::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)
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_s(cache_timestamp_format)
"#{model_name.cache_key}/#{id}-#{timestamp}"
else
"#{model_name.cache_key}/#{id}"
end
end
end
end
# 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 ActiveRecord::Base.cache_versioning is set to
# +false+ (which it is by default until Rails 6.0).
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_s(cache_timestamp_format)
end
else
if self.class.has_attribute?("updated_at")
raise ActiveModel::MissingAttributeError, "missing attribute: updated_at"
end
end
end
# Returns a cache key along with the version.
def cache_key_with_version
if version = cache_version
"#{cache_key}-#{version}"
else
cache_key
end
end
module ClassMethods
# Defines your model's +to_param+ method to generate "pretty" URLs
# using +method_name+, which can be any attribute or method that
# responds to +to_s+.
#
# class User < ActiveRecord::Base
# to_param :name
# end
#
# user = User.find_by(name: 'Fancy Pants')
# user.id # => 123
# user_path(user) # => "/users/123-fancy-pants"
#
# Values longer than 20 characters will be truncated. The value
# is truncated word by word.
#
# user = User.find_by(name: 'David Heinemeier Hansson')
# user.id # => 125
# user_path(user) # => "/users/125-david-heinemeier"
#
# Because the generated param begins with the record's +id+, it is
# suitable for passing to +find+. In a controller, for example:
#
# params[:id] # => "123-fancy-pants"
# User.find(params[:id]).id # => 123
def to_param(method_name = nil)
if method_name.nil?
super()
else
define_method :to_param do
if (default = super()) &&
(result = send(method_name).to_s).present? &&
(param = result.squish.parameterize.truncate(20, separator: /-/, omission: "")).present?
"#{default}-#{param}"
else
default
end
end
end
end
end
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.
def can_use_fast_cache_version?(timestamp)
timestamp.is_a?(String) &&
cache_timestamp_format == :usec &&
default_timezone == :utc &&
!updated_at_came_from_user?
end
# 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,
# https://github.com/postgres/postgres/commit/3e1beda2cde3495f41290e1ece5d544525810214
# to account for this we pad the output with zeros
def raw_timestamp_to_cache_version(timestamp)
key = timestamp.delete("- :.")
if key.length < 20
key.ljust(20, "0")
else
key
end
end
end
end
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