A persistent simple ruby Hash backed by sqlite3
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A persistent simple Hash backed by sqlite3

Contains (almost) the same features/API as the Ruby 2.0.0 Hash object


Add this line to your application's Gemfile:

gem 'sqlite3_hash'

And then execute:

$ bundle

Or install it yourself as:

$ gem install sqlite3_hash


SQLite3Hash is a persistent simple Hash backed by sqlite3.

You can use it like a Hash object, but all data is stored in SQLite3, which can be re-used over multiple instantiations of ruby.

Example case:

require 'rubygems'
require 'sqlite3_hash'

shash = SQLite3Hash.new('tmpfile.db')
shash['int'] = 42
shash[:sym] = { a: 12, b: 32 }
shash[99.1] = [1,[10,20],3]  
shash = nil

# Some point later..  or even in another ruby instance:
shash = SQLite3Hash.new('tmpfile.db')
shash['int']   # => 42
shash.to_s     # => {"int"=>42, :sym=>{:a=>12, :b=>32}, 99.1=>[1, [10, 20], 3]}

Handles values of String, Fixnum, Float, and anything that can be Marshalled

Keys are anything that can be Marshalled.

This means, for example, that you cannot store Procs in an SQLite3Hash

You can use the same SQLite3 DB for multiple hashes:

require 'rubygems'
require 'sqlite3_hash'
hash1 = SQLite3Hash.new('tmpfile.db','hash1')
hash2 = SQLite3Hash.new('tmpfile.db','hash2')

Contains all the Hash class methods from 2.0.0 except:

  1. No deprecated methods
  2. Methods not implemented: rehash, compare_by_identity, SQLite3Hash[]
  3. Methods that are supposed to return a hash do so (instead of returning an SQLite3Hash), for example 'to_h'
  4. try_convert also requires db and other parameters as per SQLite3Hash.new
  5. Uses the value of an object instead of the object as a key

For example:

a = [ "a", "b" ]
h = { a => 100 }
sh = SQLite3Hash('tmp.db')
a[0] = 'z'
h    # => {["z", "b"]=>100}
sh  # => {["a", "b"]=>100}


After checking out the repo, run bin/setup to install dependencies. Then, run rspec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.


Bug reports and pull requests are welcome on GitHub at https://github.com/daveola/sqlite3_hash.


The gem is available as open source under the terms of the MIT License.