activerecord/lib/active_record/counter_cache.rb
# frozen_string_literal: true
module ActiveRecord
# = Active Record Counter Cache
module CounterCache
extend ActiveSupport::Concern
included do
class_attribute :_counter_cache_columns, instance_accessor: false, default: []
class_attribute :counter_cached_association_names, instance_writer: false, default: []
end
module ClassMethods
# Resets one or more counter caches to their correct value using an SQL
# count query. This is useful when adding new counter caches, or if the
# counter has been corrupted or modified directly by SQL.
#
# ==== Parameters
#
# * +id+ - The id of the object you wish to reset a counter on.
# * +counters+ - One or more association counters to reset. Association name or counter name can be given.
# * <tt>:touch</tt> - Touch timestamp columns when updating.
# Pass +true+ to touch +updated_at+ and/or +updated_on+. Pass a symbol to
# touch that column or an array of symbols to touch just those ones.
#
# ==== Examples
#
# # For the Post with id #1, reset the comments_count
# Post.reset_counters(1, :comments)
#
# # Like above, but also touch the +updated_at+ and/or +updated_on+
# # attributes.
# Post.reset_counters(1, :comments, touch: true)
def reset_counters(id, *counters, touch: nil)
object = find(id)
updates = {}
counters.each do |counter_association|
has_many_association = _reflect_on_association(counter_association)
unless has_many_association
has_many = reflect_on_all_associations(:has_many)
has_many_association = has_many.find { |association| association.counter_cache_column && association.counter_cache_column.to_sym == counter_association.to_sym }
counter_association = has_many_association.plural_name if has_many_association
end
raise ArgumentError, "'#{name}' has no association called '#{counter_association}'" unless has_many_association
if has_many_association.is_a? ActiveRecord::Reflection::ThroughReflection
has_many_association = has_many_association.through_reflection
end
foreign_key = has_many_association.foreign_key.to_s
child_class = has_many_association.klass
reflection = child_class._reflections.values.find { |e| e.belongs_to? && e.foreign_key.to_s == foreign_key && e.options[:counter_cache].present? }
counter_name = reflection.counter_cache_column
count_was = object.send(counter_name)
count = object.send(counter_association).count(:all)
updates[counter_name] = count if count != count_was
end
if touch
names = touch if touch != true
names = Array.wrap(names)
options = names.extract_options!
touch_updates = touch_attributes_with_time(*names, **options)
updates.merge!(touch_updates)
end
unscoped.where(primary_key => [object.id]).update_all(updates) if updates.any?
true
end
# A generic "counter updater" implementation, intended primarily to be
# used by #increment_counter and #decrement_counter, but which may also
# be useful on its own. It simply does a direct SQL update for the record
# with the given ID, altering the given hash of counters by the amount
# given by the corresponding value:
#
# ==== Parameters
#
# * +id+ - The id of the object you wish to update a counter on or an array of ids.
# * +counters+ - A Hash containing the names of the fields
# to update as keys and the amount to update the field by as values.
# * <tt>:touch</tt> option - Touch timestamp columns when updating.
# If attribute names are passed, they are updated along with updated_at/on
# attributes.
#
# ==== Examples
#
# # For the Post with id of 5, decrement the comments_count by 1, and
# # increment the actions_count by 1
# Post.update_counters 5, comments_count: -1, actions_count: 1
# # Executes the following SQL:
# # UPDATE posts
# # SET comments_count = COALESCE(comments_count, 0) - 1,
# # actions_count = COALESCE(actions_count, 0) + 1
# # WHERE id = 5
#
# # For the Posts with id of 10 and 15, increment the comments_count by 1
# Post.update_counters [10, 15], comments_count: 1
# # Executes the following SQL:
# # UPDATE posts
# # SET comments_count = COALESCE(comments_count, 0) + 1
# # WHERE id IN (10, 15)
#
# # For the Posts with id of 10 and 15, increment the comments_count by 1
# # and update the updated_at value for each counter.
# Post.update_counters [10, 15], comments_count: 1, touch: true
# # Executes the following SQL:
# # UPDATE posts
# # SET comments_count = COALESCE(comments_count, 0) + 1,
# # `updated_at` = '2016-10-13T09:59:23-05:00'
# # WHERE id IN (10, 15)
def update_counters(id, counters)
id = [id] if composite_primary_key? && id.is_a?(Array) && !id[0].is_a?(Array)
unscoped.where!(primary_key => id).update_counters(counters)
end
# Increment a numeric field by one, via a direct SQL update.
#
# This method is used primarily for maintaining counter_cache columns that are
# used to store aggregate values. For example, a +DiscussionBoard+ may cache
# posts_count and comments_count to avoid running an SQL query to calculate the
# number of posts and comments there are, each time it is displayed.
#
# ==== Parameters
#
# * +counter_name+ - The name of the field that should be incremented.
# * +id+ - The id of the object that should be incremented or an array of ids.
# * <tt>:by</tt> - The amount by which to increment the value. Defaults to +1+.
# * <tt>:touch</tt> - Touch timestamp columns when updating.
# Pass +true+ to touch +updated_at+ and/or +updated_on+. Pass a symbol to
# touch that column or an array of symbols to touch just those ones.
#
# ==== Examples
#
# # Increment the posts_count column for the record with an id of 5
# DiscussionBoard.increment_counter(:posts_count, 5)
#
# # Increment the posts_count column for the record with an id of 5
# # by a specific amount.
# DiscussionBoard.increment_counter(:posts_count, 5, by: 3)
#
# # Increment the posts_count column for the record with an id of 5
# # and update the updated_at value.
# DiscussionBoard.increment_counter(:posts_count, 5, touch: true)
def increment_counter(counter_name, id, by: 1, touch: nil)
update_counters(id, counter_name => by, touch: touch)
end
# Decrement a numeric field by one, via a direct SQL update.
#
# This works the same as #increment_counter but reduces the column value by
# 1 instead of increasing it.
#
# ==== Parameters
#
# * +counter_name+ - The name of the field that should be decremented.
# * +id+ - The id of the object that should be decremented or an array of ids.
# * <tt>:by</tt> - The amount by which to decrement the value. Defaults to +1+.
# * <tt>:touch</tt> - Touch timestamp columns when updating.
# Pass +true+ to touch +updated_at+ and/or +updated_on+. Pass a symbol to
# touch that column or an array of symbols to touch just those ones.
#
# ==== Examples
#
# # Decrement the posts_count column for the record with an id of 5
# DiscussionBoard.decrement_counter(:posts_count, 5)
#
# # Decrement the posts_count column for the record with an id of 5
# by a specific amount.
# DiscussionBoard.decrement_counter(:posts_count, 5, by: 3)
#
# # Decrement the posts_count column for the record with an id of 5
# # and update the updated_at value.
# DiscussionBoard.decrement_counter(:posts_count, 5, touch: true)
def decrement_counter(counter_name, id, by: 1, touch: nil)
update_counters(id, counter_name => -by, touch: touch)
end
def counter_cache_column?(name) # :nodoc:
_counter_cache_columns.include?(name)
end
def load_schema! # :nodoc:
super
association_names = _reflections.filter_map do |name, reflection|
next unless reflection.belongs_to? && reflection.counter_cache_column
name.to_sym
end
self.counter_cached_association_names |= association_names
end
end
private
def _create_record(attribute_names = self.attribute_names)
id = super
counter_cached_association_names.each do |association_name|
association(association_name).increment_counters
end
id
end
def destroy_row
affected_rows = super
if affected_rows > 0
counter_cached_association_names.each do |association_name|
association = association(association_name)
unless destroyed_by_association && _foreign_keys_equal?(destroyed_by_association.foreign_key, association.reflection.foreign_key)
association.decrement_counters
end
end
end
affected_rows
end
def _foreign_keys_equal?(fkey1, fkey2)
fkey1 == fkey2 || Array(fkey1).map(&:to_sym) == Array(fkey2).map(&:to_sym)
end
end
end