How to set data in redis hash using ruby - ruby

Question

Currently I am caching data from active record to redis by doing following:
redis.rb
$redis = Redis::Namespace.new("bookstore", :redis => Redis.new)
authors_helper.rb
def fetch_authors
authors = $redis.get('authors')
if authors.nil?
authors = Author.all.to_json
$redis.set("authors", authors).to_json
$redis.expire("authors", 5.hour.to_i)
end
JSON.load authors
end
So currently I am using basic set and get to cache and read data from redis.
I want to use hmset instead of just set. The redis way to to this job is as follows:
(Just an example)
HMSET user:1001 name "Mary Jones" password "hidden" email "mjones#example.com"
The authors table in my app consists of following field: id ,name, created_at, updated_at
What is the ruby way to use hmset so that I can cache authors data in a redis hash?

Answer 1

I don't think you can save all authors this way. This is because a hash can store only one value for each key. So name and created_at cannot be keys, because all authors need to store their own values for these keys, but you can use each key only once.
If you're using Ruby on Rails, using Rails.cache is preferred - this way you don't have to worry about the way Rails stores the object in Redis.
However, if you want to use hmset for some reason, I believe the best you can do is something like this:
authors = Author.all.flat_map { |author| [author.id.to_s, author.attributes.to_json] }
$redis.hmset("authors", *authors_data)
The first line will return something like this:
['1', '{"name": "Mary Jones", "email": "m#example.com"}', '2', '{"name": "Another name", "email": "e#example.com"']
hmset command does not accept array, but a flat list of attributes, that's why in the 2nd line you need to pass *authors_data to the function.
Then, internally it will look like this:
{
'1' => '{"name": "Mary Jones", "email": "m#example.com"}',
'2' => '{"name": "Another name", "email": "e#example.com"'
}
Later you can do $redis.hmget("authors", '1') which will return a String '{"name": "Mary Jones", "email": "m#example.com"}'