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Diffstat (limited to 'activerecord/lib/active_record/counter_cache.rb')
| -rw-r--r-- | activerecord/lib/active_record/counter_cache.rb | 214 |
1 files changed, 214 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/counter_cache.rb b/activerecord/lib/active_record/counter_cache.rb new file mode 100644 index 0000000000..5005d58f1c --- /dev/null +++ b/activerecord/lib/active_record/counter_cache.rb @@ -0,0 +1,214 @@ +# frozen_string_literal: true + +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. + # * <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) + + 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 + + updates = { counter_name.to_sym => object.send(counter_association).count(:all) } + updates.merge!(touch_updates(touch)) if touch + + unscoped.where(primary_key => object.id).update_all(updates) + 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. + # * <tt>:touch</tt> option - 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 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) + # + # # For the Posts with id of 10 and 15, increment the comment_count by 1 + # # and update the updated_at value for each counter. + # Post.update_counters [10, 15], comment_count: 1, touch: true + # # Executes the following SQL: + # # UPDATE posts + # # SET comment_count = COALESCE(comment_count, 0) + 1, + # # `updated_at` = '2016-10-13T09:59:23-05:00' + # # WHERE id IN (10, 15) + def update_counters(id, counters) + touch = counters.delete(:touch) + + 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 + + if touch + touch_updates = touch_updates(touch) + updates << sanitize_sql_for_assignment(touch_updates) unless touch_updates.empty? + 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. + # * <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 + # # and update the updated_at value. + # DiscussionBoard.increment_counter(:posts_count, 5, touch: true) + def increment_counter(counter_name, id, touch: nil) + update_counters(id, counter_name => 1, 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>: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 + # # and update the updated_at value. + # DiscussionBoard.decrement_counter(:posts_count, 5, touch: true) + def decrement_counter(counter_name, id, touch: nil) + update_counters(id, counter_name => -1, touch: touch) + end + + private + def touch_updates(touch) + touch = timestamp_attributes_for_update_in_model if touch == true + touch_time = current_time_from_proper_timezone + Array(touch).map { |column| [ column, touch_time ] }.to_h + end + end + + private + + def _create_record(*) + id = super + + each_counter_cached_associations do |association| + if send(association.reflection.name) + association.increment_counters + 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 |