# Best way to model arbitrary-keyed Hash **URL:** \ **Category:** Rails\ **Created:** [October 3, 2006, 7:30pm UTC](https://www.ruby-forum.com/t/best-way-to-model-arbitrary-keyed-hash/70895 "2006-10-03T19:30:26Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![lynxinator](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/848f3c/32.png) [@lynxinator](https://www.ruby-forum.com/u/lynxinator)\ **Post date:** [October 3, 2006, 7:30pm UTC](https://www.ruby-forum.com/t/best-way-to-model-arbitrary-keyed-hash/70895/1 "2006-10-03T19:30:26Z")
Hi all, I’ve got an object that looks a lot like a hash, and its valid parameters are essentially arbitrary. I’m successfully storing these objects, but now I need to be able to query them. This is for my project Puppet[1], which manages many different classes of objects, like files, services, packages, and users. Each of these classes has its own set of valid parameters, and I’m adding new classes and modifying existing classes all of the time, so I don’t want to create a separate Rails table for each class. I also don’t want to create a separate table for each class because I have a ‘host’ class that functions as a collection of these objects, along with a bit of other data (like its IP address); if I have a separate table for each class, I’ll need a separate association for each one, also. I’ve been storing them using an association, with the main info (class and name) in one table, and the parameters in a separate table (e.g., the file’s owner, group, and mode) using associations. However, I expect these queries won’t work well: rails\_parameters.name = ‘owner’ and rails\_parameters.value = ‘root’ OR rails\_parameters.name = ‘owner’ and rails\_parameters.value = ‘bin’ What is the best way to store these objects so that I can easily find them? I’m assuming I can’t serialize the parameters and query against them, since SQL has no clue about the serialized YAML. Thanks, Luke 1 - [http://reductivelabs.com/projects/puppet](http://reductivelabs.com/projects/puppet) ## – Progress isn’t made by early risers. It’s made by lazy men trying to find easier ways to do something. --Robert Heinlein Luke K. | [http://reductivelabs.com](http://reductivelabs.com) | [http://madstop.com](http://madstop.com) ---
**Author:** ![lynxinator](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/848f3c/32.png) [@lynxinator](https://www.ruby-forum.com/u/lynxinator)\ **Post date:** [October 3, 2006, 8:12pm UTC](https://www.ruby-forum.com/t/best-way-to-model-arbitrary-keyed-hash/70895/2 "2006-10-03T20:12:30Z")
Hey Luke, You might want to take a look at ferret and the acts\_as\_ferret plugin. On the surface it seems like a good fit for what you are trying to accomplish. ferret - [http://ferret.davebalmain.com/trac](http://ferret.davebalmain.com/trac) aaf - [http://projects.jkraemer.net/acts\_as\_ferret/](http://projects.jkraemer.net/acts_as_ferret/) Will Groppe ---
**Author:** ![lynxinator](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/848f3c/32.png) [@lynxinator](https://www.ruby-forum.com/u/lynxinator)\ **Post date:** [October 3, 2006, 11:40pm UTC](https://www.ruby-forum.com/t/best-way-to-model-arbitrary-keyed-hash/70895/3 "2006-10-03T23:40:54Z")
William G. wrote: > Hey Luke, > > You might want to take a look at ferret and the acts\_as\_ferret plugin. > On the surface it seems like a good fit for what you are trying to > accomplish. > > ferret - [http://ferret.davebalmain.com/trac](http://ferret.davebalmain.com/trac) > aaf - [http://projects.jkraemer.net/acts\_as\_ferret/](http://projects.jkraemer.net/acts_as_ferret/) It’s good to know those are options, but I’d prefer something that maps to the database a bit more directly. ## – I don’t know the key to success, but the key to failure is trying to please everybody. – Bill Cosby Luke K. | [http://reductivelabs.com](http://reductivelabs.com) | [http://madstop.com](http://madstop.com) ---
**Author:** ![lynxinator](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/848f3c/32.png) [@lynxinator](https://www.ruby-forum.com/u/lynxinator)\ **Post date:** [October 3, 2006, 11:42pm UTC](https://www.ruby-forum.com/t/best-way-to-model-arbitrary-keyed-hash/70895/4 "2006-10-03T23:42:54Z")
On Tue, 03 Oct 2006 12:26:28 -0500 Luke K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > and modifying existing classes all of the time, so I don’t want to > create a separate Rails table for each class. I also don’t want to > create a separate table for each class because I have a ‘host’ class > that functions as a collection of these objects, along with a bit of > other data (like its IP address); if I have a separate table for each > class, I’ll need a separate association for each one, also. No way, you’re doing a Rails frontend to Puppet? Contact me off list and I’ll help you out no problem. I think there’s a few little Rails features you can use, but it sounds like you’ve gotta get the data model worked out to match what Puppet uses. Shouldn’t be that hard, but it is possible to get them all organized into the database. It also might be that you have to generalize what all of these things actually are and use attributes to differentiate them. Anyway, contact me since I’d love to help out on Puppet. – Zed A. Shaw, MUDCRAP-CE Master Black Belt Sifu > **[Zed A. shaw](https://zedshaw.com/)** > > Personal essays and writings by Zed A. Shaw. [http://mongrel.rubyforge.org/](http://mongrel.rubyforge.org/) [http://www.lingr.com/room/3yXhqKbfPy8](http://www.lingr.com/room/3yXhqKbfPy8) – Come get help. ---
**Author:** ![lynxinator](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/848f3c/32.png) [@lynxinator](https://www.ruby-forum.com/u/lynxinator)\ **Post date:** [October 4, 2006, 9:05pm UTC](https://www.ruby-forum.com/t/best-way-to-model-arbitrary-keyed-hash/70895/5 "2006-10-04T21:05:08Z")
On 10/4/06, Luke K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > It’s good to know those are options, but I’d prefer something that maps > to the database a bit more directly. > > ## – I don’t know the key to success, but the key to failure is trying to please everybody. – Bill Cosby > > Luke K. | [http://reductivelabs.com](http://reductivelabs.com) | [http://madstop.com](http://madstop.com) How about using Ferret instead of the database. Ferret basically stores hash objects which would seem to fit well for your free form classes. You could either create a new index for each class or store all objects in a single index. Querying the index will obviously be very simple. ---
**Author:** ![lynxinator](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/848f3c/32.png) [@lynxinator](https://www.ruby-forum.com/u/lynxinator)\ **Post date:** [October 4, 2006, 3:59am UTC](https://www.ruby-forum.com/t/best-way-to-model-arbitrary-keyed-hash/70895/6 "2006-10-04T03:59:14Z")
Zed A. Shaw wrote: > No way, you’re doing a Rails frontend to Puppet? Contact me off list and I’ll help you out no problem. Well, there’s already a limited Rails front-end to Puppet: [http://www.reductivelabs.com/projects/puppet/documentation/puppetshow.html](http://www.reductivelabs.com/projects/puppet/documentation/puppetshow.html) But this is actually only using ActiveRecord so I don’t have to deal with SQL or db agnosticism. > I think there’s a few little Rails features you can use, but it sounds like you’ve gotta get the data model worked out to match what Puppet uses. Shouldn’t be that hard, but it is possible to get them all organized into the database. It also might be that you have to generalize what all of these things actually are and use attributes to differentiate them. Yep, that’s exactly the trouble I’m having. Every object has a type (e.g., file) and title (e.g., “/etc/passwd”), so right now I’m just limiting querying to those two fields when using Rails. I’d like to find a db model that would allow me to find any of these objects by arbitrary attributes, rather than just these two. > Anyway, contact me since I’d love to help out on Puppet. Will do; I’d love the help. ## – Love is a snowmobile racing across the tundra and then suddenly it flips over, pinning you underneath. At night, the ice weasels come. –Matt Groening Luke K. | [http://reductivelabs.com](http://reductivelabs.com) | [http://madstop.com](http://madstop.com) ---
**Author:** ![lynxinator](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/848f3c/32.png) [@lynxinator](https://www.ruby-forum.com/u/lynxinator)\ **Post date:** [October 4, 2006, 9:35pm UTC](https://www.ruby-forum.com/t/best-way-to-model-arbitrary-keyed-hash/70895/7 "2006-10-04T21:35:11Z")
David B. wrote: > How about using Ferret instead of the database. Ferret basically > stores hash objects which would seem to fit well for your free form > classes. You could either create a new index for each class or store > all objects in a single index. Querying the index will obviously be > very simple. Does ferret to complex object queries? That is, could I do something like search for ‘obj[:owner] == “root”’? I assume that I can’t easily share a ferret index across multiple servers; it’s critical that I retain the ability to have multiple servers hit my database, both for performance and service availability. ## – The Number 1 Sign You Have Nothing to Do at Work… The 4th Division of Paperclips has overrun the Pushpin Infantry and General White-Out has called for a new skirmish. Luke K. | [http://reductivelabs.com](http://reductivelabs.com) | [http://madstop.com](http://madstop.com) ---
**Author:** ![lynxinator](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/848f3c/32.png) [@lynxinator](https://www.ruby-forum.com/u/lynxinator)\ **Post date:** [October 5, 2006, 3:35am UTC](https://www.ruby-forum.com/t/best-way-to-model-arbitrary-keyed-hash/70895/8 "2006-10-05T03:35:39Z")
On 10/5/06, Luke K. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > like search for ‘obj[:owner] == “root”’? > Yes. The query would look like this: ‘owner:“root”’. But searching for > ‘obj1[:owner] == obj2’ would be a little more difficult. Mind you, I > don’t think it would be any easier in a database. > I assume that I can’t easily share a ferret index across multiple > servers; it’s critical that I retain the ability to have multiple > servers hit my database, both for performance and service availability. You could either use a NFS to access the index (you can have multiple readers reading the index at one time) or set up a DRb server to the index. Anyway, here is a random example. I don’t really know how this would fit with how Puppet works but hopefully it gives you an idea how Ferret works. Cheers, Dave ``` require 'rubygems' require 'ferret' obj1 = {:id => 1, :children => [3, 4], :size => "large"} obj2 = {:id => 2, :children => [3, 4], :size => "small"} obj3 = {:id => 3, :parents => [1, 2], :size => "large"} obj4 = {:id => 4, :parents => [1, 2], :size => "small"} index = Ferret::I.new [obj1, obj2, obj3, obj4].each {|obj| index << obj} index.search_each('size:small AND (parents:1 OR children:3)') do ``` |id, score| puts index[id].load.inspect end ---
**Author:** ![lynxinator](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/848f3c/32.png) [@lynxinator](https://www.ruby-forum.com/u/lynxinator)\ **Post date:** [October 5, 2006, 4:59pm UTC](https://www.ruby-forum.com/t/best-way-to-model-arbitrary-keyed-hash/70895/9 "2006-10-05T16:59:00Z")
David B. wrote: > Yes. The query would look like this: ‘owner:“root”’. But searching for > ‘obj1[:owner] == obj2’ would be a little more difficult. Mind you, I > don’t think it would be any easier in a database. Ok. > You could either use a NFS to access the index (you can have multiple > readers reading the index at one time) or set up a DRb server to the > index. Anyway, here is a random example. I don’t really know how this > would fit with how Puppet works but hopefully it gives you an idea how > Ferret works. Hmmm. I’ll have to look into this more; there’s already a thread this week on puppet-dev about how important it is to be able to scale horizontally, so I don’t want to complicate that any more than I need to. > ``` > index = Ferret::I.new > > [obj1, obj2, obj3, obj4].each {|obj| index << obj} > > index.search_each('size:small AND (parents:1 OR children:3)') do |id, score| > puts index[id].load.inspect > end > > ``` Okay, cool, thanks for the example. I’ll look into it more closely, now that I know it will work for what I need. Thanks! ## – Hoare’s Law of Large Problems: Inside every large problem is a small problem struggling to get out. Luke K. | [http://reductivelabs.com](http://reductivelabs.com) | [http://madstop.com](http://madstop.com)