trivial Redis Lua scripts

redis_lua.rb

r = Redis::Namespace.new(:resque, redis: Redis.new)


# the 'correct' way. Redis wants us to specify the keys we'll be operating
# on in the script as an argument to the eval command.

script = <<-LUA
  local t = {}
  for iter,value in ipairs(KEYS) do
    table.insert(t, {value, redis.call('llen', value)})
  end
  return t
LUA
Hash[r.eval(script, r.keys("batch:*"))]      #=> {'batch:<id>' => <count>,...}



# the way where Lua does everything.
# The specifying keys thing is not enforced for now, so we can get
# away with not doing it.

script2 = <<-LUA
  local glob = ARGV[1] or "batch:*"
  local t = {}

  local keys = redis.call('keys', glob)

  for iter,value in ipairs(keys) do
    table.insert(t, {value, redis.call('llen', value)})
  end
  return t
LUA


Hash[r.eval(script2, [])]         #=> {'batch:<id>' => <count>,...}