# Model Coordination, A design problem **URL:** \ **Category:** Rails\ **Created:** [December 16, 2007, 1:31am UTC](https://www.ruby-forum.com/t/model-coordination-a-design-problem/123293 "2007-12-16T01:31:10Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![jmaenpaa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9de053/32.png) [@jmaenpaa](https://www.ruby-forum.com/u/jmaenpaa)\ **Post date:** [December 16, 2007, 1:31am UTC](https://www.ruby-forum.com/t/model-coordination-a-design-problem/123293/1 "2007-12-16T01:31:10Z")
Greating All, I have had to solve the following problem enough in the last month that I’m sure it has a name and a body of research behind it but I’m having trouble finding it. The general problem is this: I have a Site Model. Each Site has many Consumers and Producers. Producers make some amount of a “resource” available at the Site, while Consumers use these “resources.” The program’s goal is to manage changes in Consumers and Producers to keep them in balance. Questions: 1. When is it better to try to maintain a “resources” column in Site, and when is it better to reproduce the data every time. In other words is there a good way of “cashing” the resource calculation? 2. When a controller makes a change to a Consumer or Producer should the model or the controller be responsible for asking the changed items Site to rebalance its resources? 3. Is there a common name for this kind of problem that I can google/wikipedia for more information? ---
**Author:** ![jmaenpaa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9de053/32.png) [@jmaenpaa](https://www.ruby-forum.com/u/jmaenpaa)\ **Post date:** [December 16, 2007, 8:26am UTC](https://www.ruby-forum.com/t/model-coordination-a-design-problem/123293/2 "2007-12-16T08:26:48Z")
On Dec 15, 6:31 pm, John M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > changes in Consumers and Producers to keep them in balance. > > Questions: > > 1. When is it better to try to maintain a “resources” column in Site, > and when is it better to reproduce the data every time. In other words > is there a good way of “cashing” the resource calculation? As a general rule, do not store redundant information in a database, or anywhere else, until you have a known performance problem. > 1. When a controller makes a change to a Consumer or Producer should the > model or the controller be responsible for asking the changed items Site > to rebalance its resources? This one is easy. The model should be responsible. Keep the controllers as thin as possible. Ideally a controller action should fetch a model, call one method on the model, and then call a view to render that one model. ---
**Author:** ![jmaenpaa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9de053/32.png) [@jmaenpaa](https://www.ruby-forum.com/u/jmaenpaa)\ **Post date:** [December 17, 2007, 8:39pm UTC](https://www.ruby-forum.com/t/model-coordination-a-design-problem/123293/3 "2007-12-17T20:39:27Z")
kevin cline wrote: > On Dec 15, 6:31 pm, John M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > wrote: > > > changes in Consumers and Producers to keep them in balance. > > > > Questions: > > > > 1. When is it better to try to maintain a “resources” column in Site, > > and when is it better to reproduce the data every time. In other words > > is there a good way of “cashing” the resource calculation? > > As a general rule, do not store redundant information in a database, > or anywhere else, until you have a known performance problem. A little testing over the weekend reveled that i have at least two cases where changing a single Producers output ended up hitting the database 302 times and performing a sum across all producers or consumers 1437 times taking 8.34s on my SQLite :memory: database. 82% of the run time was spent in one of the adding up resources either used or consumed, 11% in data access. Given the above, I think the question becomes where and how to cache data. The concept of not storing redundant data seems prudent, but it looks like a need to do some kind of memory/processing time trade off, even it is not stored in the database. ---
**Author:** ![jmaenpaa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9de053/32.png) [@jmaenpaa](https://www.ruby-forum.com/u/jmaenpaa)\ **Post date:** [December 17, 2007, 10:28pm UTC](https://www.ruby-forum.com/t/model-coordination-a-design-problem/123293/4 "2007-12-17T22:28:01Z")
What is involved in rebalancing resources? Maybe the algorithm could be improved. ///ark ---
**Author:** ![jmaenpaa](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/9de053/32.png) [@jmaenpaa](https://www.ruby-forum.com/u/jmaenpaa)\ **Post date:** [December 17, 2007, 11:04pm UTC](https://www.ruby-forum.com/t/model-coordination-a-design-problem/123293/5 "2007-12-17T23:04:55Z")
Check out the counter cache in Rails: [#23 Counter Cache Column - RailsCasts](http://railscasts.com/episodes/23) On Dec 17, 2007 11:39 AM, John M. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)