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Rails 5.2 added method write_multi to cache store

on July 3, 2018
This blog is part of our Rails 5.2 series.

Before 5.2 it was not possible to write multiple entries to cache store in one shot even though cache stores like Redis has MSET command to set multiple keys in a single atomic operation. However we were not able to use this feature of Redis because of the way Rails had implemented caching.

Rails has implemented caching using an abstract class ActiveSupport::Cache::Store which defines the interface that all cache store classes should implement. Rails also provides few common functionality that all cache store classes will need.

Prior to Rails 5.2 ActiveSupport::Cache::Store didn't have any method to set multiple entities at once.

In Rails 5.2, write_multi was added . Each cache store can implement this method and provide the functionality to add multiple entries at once. If cache store does not implement this method, then the default implementation is to loop over each key value pair and sets it individually using write_entity method.

Multiple entities can be set as shown here.

1Rails.cache.write_multi name: 'Alan Turning', country: 'England'

redis-rails gem provides redis as cache store. However it does not implement write_multi method.

However if we are using Rails 5.2, then there is no point in using redis-rails gem, as Rails 5.2 comes with built in support for redis cache store, which implements write_multi method. It was added by this PR.

We need to make following change.

1# before
2config.cache_store = :redis_store
4# after
5config.cache_store = :redis_cache_store

redis-rails repo has a pull request to notify users that development of this gem is ceased. So it's better to use redis cache store that comes with Rails 5.2.

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