Rails: acts_as_tree and acts_as_sane_tree

Question

This is the first time I'm modelling a hierarchy within the same model (product categories).

I found a great post on this topic. Since I use Rails 4 & Postgres, which according to the article supports recursive querying (this is the first time I hear this term), the "Adjacency List With Recursive Query" seems to be the way to go because it's both easy to model and fast to query.

The article suggests the acts_as_sane_tree gem, which supports recursive querying. This repo hasn't been updated for two years and I'm not sure whether it supports Rails 4. The project is a fork of the acts_as_tree gem, which supports Rails 4 and is well maintained.

Which gem should I use? And does the acts_as_tree gem support recursive querying to avoid expensive queries?

Answer 1

If you are in doubt what gem to use, I always suggest to takes a look at the Ruby Toolbox. It helps to evaluate if a gem project is still active, how many developer using this gem and a lot more. Why do you know to do that? Do do not want to choose a gem that is not maintained anymore. You want to use the tools that the community uses and stay as close to the mainstream. If you do not follow the community you will run into problems if you need a bug fixed, further documentation or want to update your Rails version.

In this case for nested ActiveRecord awesome_nested_set and ancestry are good candidates. I would not choose the Recursive Query implementation, because most databases do not support this. Unless you have a very good reason, it is not worth to bind your app to a specific database management system.

Answer 2

have you consider ancestry gem?

"It exposes all the standard tree structure relations (ancestors, parent, root, children, siblings, descendants) and all of them can be fetched in a single SQL query."

Answer 3

I'd agree with the accepted answer on one point - it's good to go for gems that are well maintained.

On two points I disagree: Firstly, just because a gem is popular doesn't make it the right choice, or even a good choice. Taking ancestry gem as an example. It's been around a long time and is popular, but it requires you to add a special column to your tables which it fills with magic voodoo (I'm very uncomfortable with that sort of thing). Whereas a gem like acts_as_recursive_tree does all the same things as ancestry, also using single queries, but it only requires you to make a parent_id column that holds the ID of the parent - probably what you already have before even hunting for a gem. Another example - there was a gem for linking uploaded files to records. I chose to use it because it seemed the popular choice. But I ditched it as soon as I discovered it was actually modelling a many-to-many relationships, not with a joining table, but by putting comma-separated list of IDs into a single field (can you believe it?)

Secondly, if the database you have chosen has cool features like recursive query implementation, then by all means use it - that's part of the reason you chose the superior database in the first place, isn't it? Unless you have a need for you application to be database-agnostic, then don't be scared of using the features your database provides. Mitigating against the very unlikely possibility that sometime in the future you'll want to switch to a database that has less features than your current one is certainly not worth the cost of avoiding the more powerful gems that use the features of your database.

Anyway, my recommendation is acts_as_recursive_tree It's very easy to user and powerful, and actively maintained.