module ActiveRecord # = Active Record Counter Cache module CounterCache extend ActiveSupport::Concern 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. # # ==== Examples # # # For Post with id #1 records reset the comments_count # Post.reset_counters(1, :comments) def reset_counters(id, *counters) object = find(id) 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 unscoped.where(primary_key => object.id).update_all( counter_name => object.send(counter_association).count(:all) ) end return 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. # # ==== Examples # # # For the Post with id of 5, decrement the comment_count by 1, and # # increment the action_count by 1 # Post.update_counters 5, comment_count: -1, action_count: 1 # # Executes the following SQL: # # UPDATE posts # # SET comment_count = COALESCE(comment_count, 0) - 1, # # action_count = COALESCE(action_count, 0) + 1 # # WHERE id = 5 # # # For the Posts with id of 10 and 15, increment the comment_count by 1 # Post.update_counters [10, 15], comment_count: 1 # # Executes the following SQL: # # UPDATE posts # # SET comment_count = COALESCE(comment_count, 0) + 1 # # WHERE id IN (10, 15) def update_counters(id, counters) updates = counters.map do |counter_name, value| operator = value < 0 ? "-" : "+" quoted_column = connection.quote_column_name(counter_name) "#{quoted_column} = COALESCE(#{quoted_column}, 0) #{operator} #{value.abs}" end unscoped.where(primary_key => id).update_all updates.join(", ") 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. # # ==== Examples # # # Increment the posts_count column for the record with an id of 5 # DiscussionBoard.increment_counter(:posts_count, 5) def increment_counter(counter_name, id) update_counters(id, counter_name => 1) 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. # # ==== Examples # # # Decrement the posts_count column for the record with an id of 5 # DiscussionBoard.decrement_counter(:posts_count, 5) def decrement_counter(counter_name, id) update_counters(id, counter_name => -1) end end private def _create_record(*) id = super each_counter_cached_associations do |association| if send(association.reflection.name) association.increment_counters @_after_create_counter_called = true end end id end def destroy_row affected_rows = super if affected_rows > 0 each_counter_cached_associations do |association| foreign_key = association.reflection.foreign_key.to_sym unless destroyed_by_association && destroyed_by_association.foreign_key.to_sym == foreign_key if send(association.reflection.name) association.decrement_counters end end end end affected_rows end def each_counter_cached_associations _reflections.each do |name, reflection| yield association(name.to_sym) if reflection.belongs_to? && reflection.counter_cache_column end end end end