# Records in Array **URL:** \ **Category:** Rails\ **Created:** [December 14, 2009, 11:47am UTC](https://www.ruby-forum.com/t/records-in-array/180191 "2009-12-14T11:47:04Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![mercurius](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/c89c15/32.png) [@mercurius](https://www.ruby-forum.com/u/mercurius)\ **Post date:** [December 14, 2009, 11:47am UTC](https://www.ruby-forum.com/t/records-in-array/180191/1 "2009-12-14T11:47:04Z")
I have a back end admin system for a music library I’m making. I’ve atomised my data into 3 tables: Artists, Albums and Songs. They all have appropriate associations. In ‘app\views\artist\_admin\list.html.erb’ I have this code: \<%= admin\_table({:columns =\>[:name, :last\_updated], :list =\> @artists, :pages =\> @artist\_pages })%\> I want to integrate a new column that counts the number of songs that are associated with the album. Apologies if this seems trivial; I would’ve googled for this but I didn’t quite no what to search for. ---
**Author:** ![mercurius](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/c89c15/32.png) [@mercurius](https://www.ruby-forum.com/u/mercurius)\ **Post date:** [December 14, 2009, 4:01pm UTC](https://www.ruby-forum.com/t/records-in-array/180191/2 "2009-12-14T16:01:13Z")
Pale H. wrote: > I want to integrate a new column that counts the number of songs that > are associated with the album. I would recommend looking at the :counter\_cache option of belongs\_to. [http://www.railsbrain.com/api/rails-2.3.2/doc/index.html?a=M001887&name=belongs\_to](http://www.railsbrain.com/api/rails-2.3.2/doc/index.html?a=M001887&name=belongs_to) ---
**Author:** ![mercurius](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/c89c15/32.png) [@mercurius](https://www.ruby-forum.com/u/mercurius)\ **Post date:** [December 14, 2009, 4:06pm UTC](https://www.ruby-forum.com/t/records-in-array/180191/3 "2009-12-14T16:06:34Z")
Robert W. wrote: > Pale H. wrote: > > > I want to integrate a new column that counts the number of songs that > > are associated with the album. > > I would recommend looking at the :counter\_cache option of belongs\_to. > > [http://www.railsbrain.com/api/rails-2.3.2/doc/index.html?a=M001887&name=belongs\_to](http://www.railsbrain.com/api/rails-2.3.2/doc/index.html?a=M001887&name=belongs_to) However, before you do this, consider whether you actually need a counter\_cache. SQL’s count function (and its ActiveRecord interface in the Calculations module) is really the right way to do this, and you should get familiar with it first. IMHO, counter\_cache is simply a performance hack on top of that. Best, – Marnen Laibow-Koser [http://www.marnen.org](http://www.marnen.org) removed\_email\_address@domain.invalid ---
**Author:** ![mercurius](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/c89c15/32.png) [@mercurius](https://www.ruby-forum.com/u/mercurius)\ **Post date:** [December 14, 2009, 4:29pm UTC](https://www.ruby-forum.com/t/records-in-array/180191/4 "2009-12-14T16:29:46Z")
I can get Album.find(1).songs.size to work in the script console and return a valid integer but obviously I need it to be dynamic and cannot use Album.find(params[:id]).songs.size as the ID is not defined at this point. Anyway, I’ll have a look into :counter\_cache regardless. ---
**Author:** ![mercurius](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/c89c15/32.png) [@mercurius](https://www.ruby-forum.com/u/mercurius)\ **Post date:** [December 14, 2009, 7:15pm UTC](https://www.ruby-forum.com/t/records-in-array/180191/5 "2009-12-14T19:15:18Z")
Marnen Laibow-Koser wrote: > However, before you do this, consider whether you actually need a > counter\_cache. SQL’s count function (and its ActiveRecord interface in > the Calculations module) is really the right way to do this, and you > should get familiar with it first. IMHO, counter\_cache is simply a > performance hack on top of that. Pale H. wrote: > I want to integrate a new column that counts the number of songs that > are associated with the album. You’re absolutely right. I should have mentioned that. I was being too literal in answering this part of the OP. I agree with you that counter\_cache could certainly be considered pre-mature optimization. By the way. Does Rails override the “size” method on an association by using a SQL count? Or, must one use the “count” method to get that behavior? Album.find(1).songs.size could be really bad if it does not. ---
**Author:** ![mercurius](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/c89c15/32.png) [@mercurius](https://www.ruby-forum.com/u/mercurius)\ **Post date:** [December 14, 2009, 7:56pm UTC](https://www.ruby-forum.com/t/records-in-array/180191/6 "2009-12-14T19:56:07Z")
Robert W. wrote: > Robert W. wrote: > Ugh! Sorry for the bad posting order in the previous reply. I intended > the response be directed to Marnen. Then use quoting in your replies to make it clear. Remember that this is primarily a mailing list, even though many of us use the Web forum interface. Best, – Marnen Laibow-Koser [http://www.marnen.org](http://www.marnen.org) removed\_email\_address@domain.invalid ---
**Author:** ![mercurius](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/c89c15/32.png) [@mercurius](https://www.ruby-forum.com/u/mercurius)\ **Post date:** [December 14, 2009, 7:17pm UTC](https://www.ruby-forum.com/t/records-in-array/180191/7 "2009-12-14T19:17:02Z")
Robert W. wrote: Ugh! Sorry for the bad posting order in the previous reply. I intended the response be directed to Marnen.