# Persistent Hash **URL:** \ **Category:** Ruby\ **Created:** [May 9, 2008, 11:23pm UTC](https://www.ruby-forum.com/t/persistent-hash/137200 "2008-05-09T23:23:28Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![kyle\_s](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/f6c823/32.png) [@kyle\_s](https://www.ruby-forum.com/u/kyle_s)\ **Post date:** [May 9, 2008, 11:23pm UTC](https://www.ruby-forum.com/t/persistent-hash/137200/1 "2008-05-09T23:23:28Z")
I’m looking for some sort of persistent hash, or object store for ruby. I just need some advice about what works well & doesn’t, so I don’t attempt to \*re-invent the wheel. I’d be using it for a some small client-server apps, maybe web front end, maybe not, but either way, I’m guessing multiple processes will want to access the data simultaneously. The options I’ve come up with are 1 DBM/SDBM + YAML 2 PStore 3 Marshall 4 ActiveRecord 1 I really didn’t see much in the way of DBM/SDBM documentation, but may be I was looking in the wrong places. All the same, I can see pretty easily how I could do something like a persistent hash by combining yaml and DBM, but it does make me wonder, has anyone already done something like that? 2 PStore seems a little clunky, but rather effective: How is it with medium sized data sets (hashes of a few thousand elements)? How is over the longer term, data resiliency wise? 3 Marshalling and un-marshalling I know will work, but at the same time it seems… well a bit prosaic. 4 ActiveRecord I know will work, and I’ve played with before, but I really don’t like how it forces you to hammer your data structure into it’s mold. \*yes re-inventing the wheel is a time honored and important past-time for programmers. It’s fun, it teaches you things, but when you really want to work on another part of a project, you have to force yourself not to. ---
**Author:** ![kyle\_s](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/f6c823/32.png) [@kyle\_s](https://www.ruby-forum.com/u/kyle_s)\ **Post date:** [May 10, 2008, 12:12am UTC](https://www.ruby-forum.com/t/persistent-hash/137200/2 "2008-05-10T00:12:42Z")
DataMapper [[http://datamapper.org/](http://datamapper.org/) ] and Sequel [ [http://sequel.rubyforge.org/](http://sequel.rubyforge.org/) ] might be options for you. I haven’t used them (yet); I just know that they’re there. Regards, Craig ---
**Author:** ![kyle\_s](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/f6c823/32.png) [@kyle\_s](https://www.ruby-forum.com/u/kyle_s)\ **Post date:** [May 10, 2008, 12:36am UTC](https://www.ruby-forum.com/t/persistent-hash/137200/3 "2008-05-10T00:36:41Z")
DataMapper +1 Sent from my iPhone On May 9, 2008, at 6:12 PM, “Craig D.” ---
**Author:** ![kyle\_s](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/f6c823/32.png) [@kyle\_s](https://www.ruby-forum.com/u/kyle_s)\ **Post date:** [May 10, 2008, 3:24am UTC](https://www.ruby-forum.com/t/persistent-hash/137200/4 "2008-05-10T03:24:02Z")
On Fri, May 9, 2008 at 10:22 PM, Kyle S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I’m looking for some sort of persistent hash, or object store for ruby. I quite like fsdb - [FSDB](http://redshift.sourceforge.net/fsdb/). It persists data in the filesystem, is multi-thread and multi-process safe (as far as flock is safe) and works nicely with yaml. From the docs: require ‘fsdb’ db = FSDB::Database.new(‘/tmp/my-data’) db[‘recent-movies/myself’] = [“LOTR II”, “Austin Powers”] puts db[‘recent-movies/myself’][0] # ==\> “LOTR II” db.edit ‘recent-movies/myself’ do |list| list \<\< “A la recherche du temps perdu” end Not sure if it hasn’t been updated because it’s stable or because development has stopped. I used it for a note-taking application which I had running for a couple of years. Never had a problem with it (though I wasn’t exactly stressing it). Regards, Sean ---
**Author:** ![kyle\_s](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/f6c823/32.png) [@kyle\_s](https://www.ruby-forum.com/u/kyle_s)\ **Post date:** [May 10, 2008, 10:31am UTC](https://www.ruby-forum.com/t/persistent-hash/137200/5 "2008-05-10T10:31:10Z")
On 09.05.2008 23:22, Kyle S. wrote: > 2 PStore seems a little clunky, but rather effective: How is it with > medium sized data sets (hashes of a few thousand elements)? How is > over the longer term, data resiliency wise? Might be an option, depending on how long your transactions are. If they are short you might get away with doing a file lock on the store to ensure concurrency safety. If transactions are longer or load is higher you better use a relational database. > 3 Marshalling and un-marshalling I know will work, but at the same > time it seems… well a bit prosaic. Marshal isn’t really an option as it requires too much work around it to make it concurrency safe IMHO. PStore is basically Marshal with transactional behavior added. You do not mention DBI, i.e. writing your SQL yourself. If your application has to cope with significant concurrency (i.e. high number of concurrent requests and / or long transactions) a RDBMS will give you the best results IMHO because it contains mechanisms that deal with this. Note that you can for example use the free version of Oracle or Postgres, MySQL etc. Kind regards robert ---
**Author:** ![kyle\_s](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/f6c823/32.png) [@kyle\_s](https://www.ruby-forum.com/u/kyle_s)\ **Post date:** [May 10, 2008, 7:35pm UTC](https://www.ruby-forum.com/t/persistent-hash/137200/6 "2008-05-10T19:35:00Z")
Sean O’Halpin wrote: > development has stopped. I used it for a note-taking application which > I had running for a couple of years. Never had a problem with it > (though I wasn’t exactly stressing it). > > Regards, > Sean It’s stable, AFAIK. It’s running as part of a couple of my projects and I just sort of forget it’s there. Whether it is a good fit depends on the requirements. OP mentioned: small apps, multiple processes accessing the database. That sounds like fsdb. In this case the main advantage over PStore will be breaking up “a few thousand elements” into separate files. PStore uses one big file, FSDB uses the file system itself. You can decide what granularity you want–how much gets dumped into files vs. how many files/dirs. And you’re free to choose the serialization method for each file (typically based on filename extension)–yaml, marshal, or something else. YAML is a bit slower and more limited than Marshal, but you end up with a database that can be edited with a text editor. There are limitations, of course. For example, there’s no automatic way to manage references between objects stored in separate files. Kirbybase is something else that’s often mentioned in these discussions, but I don’t know it well… ---
**Author:** ![kyle\_s](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/f6c823/32.png) [@kyle\_s](https://www.ruby-forum.com/u/kyle_s)\ **Post date:** [May 11, 2008, 3:08am UTC](https://www.ruby-forum.com/t/persistent-hash/137200/7 "2008-05-11T03:08:56Z")
ara.t.howard wrote: > On May 10, 2008, at 11:34 AM, Joel VanderWerf wrote: > > > It’s stable, AFAIK. It’s running as part of a couple of my projects > > and I just sort of forget it’s there. > > i think this project is one of the most under-rated out there - you > should push it on the list a bit as i’ve personally found it really > useful in the past and am always suprised more people don’t know about it. Er, you mean like making a gem out of it… yeah I guess so 🙂 ---
**Author:** ![kyle\_s](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/k/f6c823/32.png) [@kyle\_s](https://www.ruby-forum.com/u/kyle_s)\ **Post date:** [May 11, 2008, 12:48am UTC](https://www.ruby-forum.com/t/persistent-hash/137200/8 "2008-05-11T00:48:32Z")
On May 10, 2008, at 11:34 AM, Joel VanderWerf wrote: > It’s stable, AFAIK. It’s running as part of a couple of my projects > and I just sort of forget it’s there. i think this project is one of the most under-rated out there - you should push it on the list a bit as i’ve personally found it really useful in the past and am always suprised more people don’t know about it. cheers. a @ [http://codeforpeople.com/](http://codeforpeople.com/)