#!/usr/bin/ruby
require 'groonga'

FILENAME = '/tmp/test.db'
MAX_RECORDS = 2

begin
  db = Groonga::Database.open(FILENAME)
rescue
  db = Groonga::Database.create(:path => FILENAME)
end

unless user_table = Groonga::Context.default['User']
  user_table = Groonga::Hash.create(
    :name => 'User',
    :key_type => 'UInt32', # 主キーは数値！
    :persistent => true)
end

unless community_table = Groonga::Context.default['Community']
  community_table = Groonga::Hash.create(
    :name => 'Community',
    :key_type => 'ShortText',
    :persistent => true)
  community_table.define_column('mtime', 'Time', {:persistent => true})
  community_table.define_column('users', user_table, {:persistent => true, :type => :vector})
end

user_table.truncate
community_table.truncate

communities = [['co1',  1263816091, [2, 3, 5, 6]],
               ['co4',  1263816090, [2, 3]],
               ['co9',  1263816089, [2]],
               ['co15', 1263816092, []],
              ]

communities.each {|id, mtime, users|
  rec = community_table.add(id)
  rec['mtime'] = Time.at(mtime)
  rec['users'] = users.map{|u| user_table.add(u)}
}

# 主キーが2であるユーザが加入しているコミュニティを、mtimeが新しい順に2つ取得。つまり、'co1', 'co4'を取得
recs = community_table.select('users:@2')
i = 0
recs.sort([{:key => 'mtime', :order => 'descending'}]).each {|r|
  rec = r.key
  puts "community: #{rec.key}"
  i += 1
  break if i >= MAX_RECORDS
}