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#2009 ✓resolved
Alexandre da Silva

Counter cache not used for size and count through has_many associations

Reported by Alexandre da Silva | February 18th, 2009 @ 06:24 PM | in 2.x

counter_cache feature is not working correctly with rails version 2.2.2 and 2.3.0 RC1

The counter is incrementing and decrementing as well, but the size and count methods, over association are issuing a SQL COUNT to the database on every call.

to reproduce create a new rails application (2.2.2 or 2.3RC1) define the migrations ans models as folows:

create_table :projects do |t|
  t.string :name
  t.integer :tasks_count

create_table :tasks do |t|
  t.references :project
  t.string :name

class Project < ActiveRecord::Base
  has_many :tasks

class Task < ActiveRecord::Base
  belongs_to :project, :counter_cache => true

Open up a console and see the log:

p = Project.create :name => 'My Project'
>>   Project Create (0.5ms)   INSERT INTO "projects" ("name", "tasks_count", "created_at", "updated_at") VALUES('My Project', NULL, '2009-02-18 18:02:28', '2009-02-18 18:02:28')
p.tasks.create :name => 'Task 1'
>> Task Create (0.7ms)   INSERT INTO "tasks" ("name", "created_at", "project_id", "updated_at") VALUES('Task 1', '2009-02-18 18:03:45', 1, '2009-02-18 18:03:45')
>>  Project Load (0.8ms)   SELECT * FROM "projects" WHERE ("projects"."id" = 1) 
>>  Project Update (0.4ms)   UPDATE "projects" SET "tasks_count" = COALESCE("tasks_count", 0) + 1 WHERE ("id" = 1) 
p.tasks.create :name => 'Task 2'
>> Task Create (0.7ms)   ... UPDATE "projects" SET "tasks_count"...
p.tasks.create :name => 'Task 3'
>>  Task Create (0.7ms)  ... UPDATE "projects" SET "tasks_count"...
>> SQL (0.6ms)   SELECT count(*) AS count_all FROM "tasks" WHERE ("tasks".project_id = 1)
>> SQL (0.6ms)   SELECT count(*) AS count_all FROM "tasks" WHERE ("tasks".project_id = 1)

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