module ActiveRecord::CounterCache::ClassMethods
Public instance methods
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. -
:by
- The amount by which to decrement the value. Defaults to1
. -
:touch
- Touch timestamp columns when updating. Passtrue
to touchupdated_at
and/orupdated_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)
Source code GitHub
# File activerecord/lib/active_record/counter_cache.rb, line 178
def decrement_counter(counter_name, id, by: 1, touch: nil)
update_counters(id, counter_name => -by, touch: touch)
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. -
:by
- The amount by which to increment the value. Defaults to1
. -
:touch
- Touch timestamp columns when updating. Passtrue
to touchupdated_at
and/orupdated_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)
Source code GitHub
# File activerecord/lib/active_record/counter_cache.rb, line 148
def increment_counter(counter_name, id, by: 1, touch: nil)
update_counters(id, counter_name => by, touch: touch)
end
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. -
:touch
- Touch timestamp columns when updating. Passtrue
to touchupdated_at
and/orupdated_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)
Source code GitHub
# File activerecord/lib/active_record/counter_cache.rb, line 34
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. -
:touch
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)
Source code GitHub
# File activerecord/lib/active_record/counter_cache.rb, line 115
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