Allow fetching multiple values from the cache at once

Add a simple API for fetching a list of entries from the cache, where
any missing entries are computed by a supplied block.

1 files changed, 28 insertions, 0 deletions

diff --git a/activesupport/lib/active_support/cache.rb b/activesupport/lib/active_support/cache.rb
index 6c220ae625..b1ab5570a8 100644
--- a/activesupport/lib/active_support/cache.rb
+++ b/activesupport/lib/active_support/cache.rb
@@ -352,6 +352,34 @@ module ActiveSupport
         results
       end
 
+      # Fetches data from the cache, using the given keys. If there is data in
+      # the cache with the given keys, then that data is returned. Otherwise,
+      # the supplied block is called for each key for which there was no data,
+      # and the result will be written to the cache and returned.
+      #
+      # Options are passed to the underlying cache implementation.
+      #
+      # Returns an array with the data for each of the names. For example:
+      #
+      #   cache.write("bim", "bam")
+      #   cache.fetch_multi("bim", "boom") {|key| key * 2 }
+      #   #=> ["bam", "boomboom"]
+      #
+      def fetch_multi(*names)
+        options = names.extract_options!
+        options = merged_options(options)
+
+        results = read_multi(*names, options)
+
+        names.map do |name|
+          results.fetch(name) do
+            value = yield name
+            write(name, value, options)
+            value
+          end
+        end
+      end
+
       # Writes the value to the cache, with the key.
       #
       # Options are passed to the underlying cache implementation.