# "Materialized Paths" Hierarchies and Rails **URL:** \ **Category:** Rails\ **Created:** [December 16, 2006, 5:22pm UTC](https://www.ruby-forum.com/t/materialized-paths-hierarchies-and-rails/79566 "2006-12-16T17:22:21Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![dcarneiro](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/e36b37/32.png) [@dcarneiro](https://www.ruby-forum.com/u/dcarneiro)\ **Post date:** [December 16, 2006, 5:22pm UTC](https://www.ruby-forum.com/t/materialized-paths-hierarchies-and-rails/79566/1 "2006-12-16T17:22:21Z")
Folks, I’ve done some cursory googling and seen nothing promising. . . I’m interested in implementing an “acts\_as\_materialized\_path” plugin, which offers a way to model hierarchies in a way that can have significant advantages over the “adjacency list” provided by acts\_as\_tree and the nested set provided by “acts\_as\_nested\_set”. I’m the author of perl’s DBIx::Tree::NestedSet ( [http://cpan.uwinnipeg.ca/dist/DBIx-Tree-NestedSet](http://cpan.uwinnipeg.ca/dist/DBIx-Tree-NestedSet) ), if it matters. I’d be happy to talk about the relative advantages of the adjacency list, nested set and materialized path hierarchy models, but that’s not the point of this posting. I’m pinging the community to make sure I’m not going to be duplicating effort and to gauge interest. Thoughts? Comments? Criticisms? Pointers? Thanks in advance. -DJCP ---
**Author:** ![dcarneiro](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/e36b37/32.png) [@dcarneiro](https://www.ruby-forum.com/u/dcarneiro)\ **Post date:** [December 16, 2006, 7:23pm UTC](https://www.ruby-forum.com/t/materialized-paths-hierarchies-and-rails/79566/2 "2006-12-16T19:23:58Z")
Hi Daniel, I’ve been helping Jean-Christophe M. with the Better Nested Set plugin ([http://opensource.symetrie.com/trac/better\_nested\_set](http://opensource.symetrie.com/trac/better_nested_set)). I’m interested in anything that offers efficient management of large hierarchical data-sets in Rails, so I’d love to see a materialized path implementation. Regarding development, I would like to share thoughts and ideas (at a minimum, I suppose it would be good if we tried to keep the APIs similar). In any case, please keep me updated on what you do. I’m looking at your DBIx module, but as someone who’s never used Perl, I’m wondering how to generate the documentation (how do you say ‘rake rdoc’ in Perl?). You’ve probably already looked at Better Nested Set, but if not, you can install it with: script/plugin install svn://rubyforge.org/var/svn/betternestedset/trunk then run ‘rake rdoc’ in the betternestedset directory. Cheers, Krishna On Dec 16, 11:22 am, Daniel Collis-puro ---
**Author:** ![dcarneiro](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/e36b37/32.png) [@dcarneiro](https://www.ruby-forum.com/u/dcarneiro)\ **Post date:** [December 16, 2006, 9:59pm UTC](https://www.ruby-forum.com/t/materialized-paths-hierarchies-and-rails/79566/3 "2006-12-16T21:59:05Z")
kpd wrote: > Hi Daniel, > > I’ve been helping Jean-Christophe M. with the Better Nested Set > plugin ([http://opensource.symetrie.com/trac/better\_nested\_set](http://opensource.symetrie.com/trac/better_nested_set)). > > I’m interested in anything that offers efficient management of large > hierarchical data-sets in Rails, so I’d love to see a materialized path > implementation. Regarding development, I would like to share thoughts > and ideas (at a minimum, I suppose it would be good if we tried to keep > the APIs similar). In any case, please keep me updated on what you do. I will! > I’m looking at your DBIx module, but as someone who’s never used Perl, > I’m wondering how to generate the documentation (how do you say ‘rake > rdoc’ in Perl?). You can get the docs online (see the links at the bottom of the page) at: [http://search.cpan.org/~djcp/DBIx-Tree-NestedSet-0.16/](http://search.cpan.org/~djcp/DBIx-Tree-NestedSet-0.16/) Or, if you’ve installed the module via CPAN or the normal “perl Makefile.PL; make ; make test ; make install” dance, via “perldoc DBIx::Tree::NestedSet” in your console of choice. BTW, this module has been running in production apps of mine for three years without a problem. I need to give it another revision, though. . . > You’ve probably already looked at Better Nested Set, but if not, you > can install it with: > script/plugin install > svn://rubyforge.org/var/svn/betternestedset/trunk > then run ‘rake rdoc’ in the betternestedset directory. I definitely did take a look at it and I plan on testing it and maybe using it as a model for how my materialized path works. I think it’d be awesome of have a standard API so that you can easily switch between schemes. The big advantage of having a consistent API would be flexibility. For instance: Nested sets kick butt in applications where there are many reads but few updates/deletes, but performance becomes a concern when you start fiddling with the tree a lot. You need to lock pretty much the entire tree when you do an update or you could face consistency problems (which are very hard to fix in a nested set. . . ). Materialized paths are easily understood, high performance and don’t require the recursive queries an adjacency list does. If we had a consistent API, one could swap out hierarchical representations as an app changes, letting you focus on what your app needs and what representation suits it best. How cool would it be if changing between the two plugins would automatically convert the tree behind the scenes. . . Maybe the best way we could work together now would be to standardize the API - I know nested sets pretty well, and we can define an API that’ll offer the flexibility we need for both implementations. -DJCP ---
**Author:** ![dcarneiro](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/e36b37/32.png) [@dcarneiro](https://www.ruby-forum.com/u/dcarneiro)\ **Post date:** [December 19, 2006, 4:32am UTC](https://www.ruby-forum.com/t/materialized-paths-hierarchies-and-rails/79566/4 "2006-12-19T04:32:58Z")
On Dec 16, 3:59 pm, Daniel Collis-puro [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > awesome of have a standard API so that you can easily switch between > schemes. Definitely. Let’s plan on it. > changing between the two plugins would automatically convert the tree > behind the scenes. . . I’m not sure about automagically adding columns to the table, but we’ve made the rest of it pretty easy in BetterNestedSet: once you have the columns, just run a single method and it turns your existing ordinary (adjacency list) trees into nested sets. > Maybe the best way we could work together now would be to standardize > the API - I knownestedsets pretty well, and we can define an API > that’ll offer the flexibility we need for both implementations. Sounds like a plan. After you get a chance to look over the BetterNestedSet API, let us know what changes/extensions you might want. I’m actually playing with some experimental changes to how our API works, so I’ll try to get those committed soon. Would you like to continue this discussion here, or move it to the BetterNestedSet mailing list? ([http://rubyforge.org/mailman/listinfo/betternestedset-talk](http://rubyforge.org/mailman/listinfo/betternestedset-talk)) Cheers, looking forward to hashing it out. k