SQLite-powered Key/Value Store

litestore.rb

require 'yaml'
require 'digest/sha2'
require 'rubygems'
require 'sequel'


class LiteStore

  attr_reader :artifacts
  attr_reader :db

  def initialize
    # Initializes an in-memory SQLite DB
    @db = Sequel.sqlite
    @artifacts = @db[:artifacts]
    # Default table
    @db.create_table :artifacts do
      String :key
      String :content, :text => true
    end
    # An example index table
    @db.create_table :message do
      String :ref
      String :content
      index :content
    end
  end

  def get(key)
    @artifacts.first :key => key
  end

  def post(object)
    key = Digest::SHA2.hexdigest(Time.now.to_s+rand(100).to_s)
    @db.transaction do
      @artifacts.insert :key => key, :content =>object.to_yaml
      # TODO: Error handling
      object.class.indices.each do |i|
        @db[i.values[0]].insert :ref => key, :content => object.send(i.keys[0])
      end
    end
    key
  end

  def put(key, object)
    # TODO: Update indices
    @artifacts.update :key => key, :content => object.to_yaml
    key
  end

  def delete(key)
    # TODO: Delete indices
    @artifacts.delete :key => key
    key
  end

  def find(*conditions) # "column <operator> value"
    refs = []
    # Find references in indexes based on conditions supplied -- Very basic for now!
    conditions.each do |cond|
      condition = cond.gsub /^(.+?)\s/, 'content ' # TODO: Error handling
      result =  @db[$1.to_sym].select(:ref).filter(condition).all
      refs = (refs == []) ? result : refs & result 
    end
    # get artifacts matching refs
    @artifacts.filter(:key => refs.map{|v| v[:ref]}).all
  end

end

class Object

  class << self; attr_accessor :indices; end

  def self.index(pair) # :property => :index_table
    self.indices ||= []
    self.indices << pair
  end

end

######################

class Message
  
  attr_accessor :text, :created_at

  def initialize(message)
    @text = message
    @created_at = Time.now
  end

end

Message.index :text => :message

a = Message.new "Test #1"
b = Message.new "Test #2"

ls = LiteStore.new

ls.post(a)
ls.post(b)
puts ls.find("message = 'Test #1'").to_yaml