如何使用Ruby通过HMSET在Redis哈希中存储ActiveRecord缓存数据

Got it, let's adjust your current Redis caching setup from basic SET/GET to using HMSET (or the recommended HSET for newer Redis versions). Here's a practical implementation that keeps your workflow intact while leveraging Redis hash structures:

Step 1: Understand the Hash Structure #

Instead of storing all authors as a single JSON string under one key, we'll use a Redis hash where:

• The top-level key remains authors
• Each field in the hash is an author's ID (as a string)
• Each value is the JSON-serialized data of that author

This approach lets you update individual author entries later without re-caching the entire list—way more efficient!

Step 2: Updated Helper Code #

Modify your authors_helper.rb like this:

def fetch_authors
  # Fetch all entries from the Redis hash
  authors_cache = $redis.hgetall('authors')

  if authors_cache.empty?
    # Cache miss: pull data from DB
    authors = Author.all

    # Build a hash mapping author IDs to their JSON data
    author_entries = authors.each_with_object({}) do |author, hash|
      hash[author.id.to_s] = author.to_json
    end

    # Use HMSET to populate the Redis hash (flatten the hash into key-value pairs)
    $redis.hmset('authors', *author_entries.flatten)

    # Set expiration for the entire hash key (same 5-hour window as before)
    $redis.expire('authors', 5.hour.to_i)

    # Return the fresh DB records
    authors
  else
    # Cache hit: parse JSON values and return as an array of author data
    authors_cache.values.map { |json| JSON.parse(json) }
  end
end

Notes for Redis Versions 4.0+ #

HMSET has been deprecated in newer Redis versions in favor of HSET, which supports setting multiple field-value pairs directly. If you're running Redis 4.0 or later, you can replace the hmset line with:

# Directly pass the hash to HSET (Ruby client handles the conversion)
$redis.hset('authors', author_entries)

Bonus: Updating Individual Authors #

One of the perks of using a hash is being able to update a single author's cache without reloading the whole list. For example:

def update_author_cache(author)
  $redis.hset('authors', author.id.to_s, author.to_json)
end

This keeps your cache fresh for specific entries without wasting resources on re-caching everything.

内容的提问来源于stack exchange，提问作者user3576036