From 476e3f552f59d208cb284f509760b44ad780c17a Mon Sep 17 00:00:00 2001 From: "Alberto F. Capel" Date: Tue, 14 Jul 2015 23:47:16 +0100 Subject: Add #cache_key to ActiveRecord::Relation. --- activerecord/lib/active_record/relation.rb | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) (limited to 'activerecord/lib/active_record/relation.rb') diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb index e4df122af6..3ed04dee3b 100644 --- a/activerecord/lib/active_record/relation.rb +++ b/activerecord/lib/active_record/relation.rb @@ -298,6 +298,32 @@ module ActiveRecord limit_value ? to_a.many? : size > 1 end + # 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. + def cache_key(timestamp_column = :updated_at) + @cache_keys ||= {} + @cache_keys[timestamp_column] ||= @klass.collection_cache_key(self, timestamp_column) + end + # Scope all queries to the current scope. # # Comment.where(post_id: 1).scoping do -- cgit v1.2.3