method

cache_key

v5.0.0.1 - Show latest stable - 0 notes - Class: ActiveRecord::Relation

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What's this?

cache_key(timestamp_column = :updated_at) public

Returns a cache key that can be used to identify the records fetched by this query. The cache key is built with a fingerprint of the sql query, the number of records matched by the query and a timestamp of the last updated record. When a new record comes to match the query, or any of the existing records is updated or deleted, the cache key changes.

Product.where("name like ?", "%Cosmic Encounter%").cache_key
# => "products/query-1850ab3d302391b85b8693e941286659-1-20150714212553907087000"

If the collection is loaded, the method will iterate through the records to generate the timestamp, otherwise it will trigger one SQL query like:

SELECT COUNT(*), MAX("products"."updated_at") FROM "products" WHERE (name like '%Cosmic Encounter%')

You can also pass a custom timestamp column to fetch the timestamp of the last updated record.

Product.where("name like ?", "%Game%").cache_key(:last_reviewed_at)

You can customize the strategy to generate the key on a per model basis overriding ActiveRecord::Base#collection_cache_key.

Show source

# File activerecord/lib/active_record/relation.rb, line 335
    def cache_key(timestamp_column = :updated_at)
      @cache_keys ||= {}
      @cache_keys[timestamp_column] ||= @klass.collection_cache_key(self, timestamp_column)
    end

cache_key

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