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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.
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dasch committed Apr 15, 2013
1 parent 6023a50 commit 36d41a15c35e6f4b698931987b2115e221d0fcfa
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
@@ -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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