Where does Search fit into the MVC software pattern?

Question

I am implementing a database search algorithm which searches over many collections in a MongoDB and returns optimized results based on the state of the entire database. I have no problems with the implementation, but the nomenclature and how I should structure the file system is bugging me. Where in the model-view-controller pattern should I place read only operations? Is it a service? It has a controller but I hardly think it satisfies the criteria to be a model.

Answer 1

This question is extremely language dependant and the features that exist within that language. I will speak from a PHP point of view.

Search functions should go into the model, the model backs up as a data provider in the MVC pattern. A single central point from which to dish out instances of it self.

Some MVCs implement what is known as factory classes. They are specifically designed to sit outside of the MVCs normal pattern to be able to provide data: http://en.wikipedia.org/wiki/Factory_method_pattern . As someone who has used this pattern I can say it gets complicated and unmanageable very quickly. That is why I prefer to backup the model as a data provider itself, it merely requires class organisation.

Answer 2

Model View Controller architecture is pretty much the equivalent of a three or four tier solution in a client server setup and the same rules apply.

Complex and intensive database functionality lives with the tool that is best suited to the task and is most re-usable and in this case I would argue that the RDBMS would be the best option in the vast majority of RDBMS's as it is the RDBMS that best knows how to manipulate it's data, work out query plans etc...

It could also be argued that the model layer would be the most natural place from a purist coding point of view where you have all your data access in one layer.

It is highly unlikely that it would ever be advantageous to place this sort of functionality in the least re-usable layer i.e. the controller/view

This is of course only my opinion and I suspect you will get many alternative opinions but ( can not for the life of me think that from a performance point of view that yopur logic belongs anywhere other than at the database level

UPDATE

A model is the guardian of all data. if a view or controller wants data, it asks the model for that data. The view or controller shouldn't care about how the data is obtained or where it comes from. It's about separation of concerns. So that leaves the question. Do I place the code to query the database in the model or in the RDBMS?

Well of course you have to have a method in a model for the view or controller to call in the first place so of course you need a model but what goes inside that method and where the actual query SQL lives is up to the designer. The point is, that so long as the query lives at model or database level you are hiding the implementation from the view or controller and are free to change the implementation whenever you wish without having to worry about the potentially many places it is called from.

So model or RDBMS is the answer. The solution chosen depends on the MVC tools you are using and the RDBMS you are using. Also remember that a model does not have to consist of a single method which is what you are implying you may be thinnking from your comment.