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Merge pull request #10234 from dasch/dasch/fetch-multi

Allow fetching multiple values from the cache at once
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2 parents 925728c + 36d41a1 commit 33283c98ed690b12bc2bca75276236dc907798b2 @rafaelfranca rafaelfranca committed May 7, 2013
Showing with 61 additions and 1 deletion.
  1. +13 −1 activesupport/CHANGELOG.md
  2. +28 −0 activesupport/lib/active_support/cache.rb
  3. +20 −0 activesupport/test/caching_test.rb
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@@ -1,3 +1,15 @@
-* No changes.
+* Add a `fetch_multi` method to the cache stores. The method provides
+ an easy to use API for fetching multiple values from the cache.
+
+ Example:
+
+ # Calculating scores is expensive, so we only do it for posts
+ # that have been updated. Cache keys are automatically extracted
+ # from objects that define a #cache_key method.
+ scores = Rails.cache.fetch_multi(*posts) do |post|
+ calculate_score(post)
+ end
+
+ *Daniel Schierbeck*
Please check [4-0-stable](https://github.com/rails/rails/blob/4-0-stable/activesupport/CHANGELOG.md) for previous changes.
@@ -352,6 +352,34 @@ def read_multi(*names)
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.
@@ -257,6 +257,26 @@ def test_read_multi_with_expires
assert_equal({"fu" => "baz"}, @cache.read_multi('foo', 'fu'))
end
+ def test_fetch_multi
+ @cache.write('foo', 'bar')
+ @cache.write('fud', 'biz')
+
+ values = @cache.fetch_multi('foo', 'fu', 'fud') {|value| value * 2 }
+
+ assert_equal(["bar", "fufu", "biz"], values)
+ assert_equal("fufu", @cache.read('fu'))
+ end
+
+ def test_multi_with_objects
+ foo = stub(:title => "FOO!", :cache_key => "foo")
+ bar = stub(:cache_key => "bar")
+
+ @cache.write('bar', "BAM!")
+
+ values = @cache.fetch_multi(foo, bar) {|object| object.title }
+ assert_equal(["FOO!", "BAM!"], values)
+ end
+
def test_read_and_write_compressed_small_data
@cache.write('foo', 'bar', :compress => true)
assert_equal 'bar', @cache.read('foo')

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