This project is archived and is in readonly mode.
Rails.cache.fetch does not work with false boolean as cached value
Reported by Thijs de Vries | January 31st, 2009 @ 10:19 PM | in 3.x
If I run
some_bool_value = Rails.cache.fetch("some_key") {expensive_function_returns_false()}
Rails will miss on the fetch every time. However if I do
if Rails.cache.exist?("some_key")
some_bool_value = Rails.cache.read("some_key")
else
some_bool_value = Rails.cache.write("some_key", expensive_function_returns_false())
end
The cache will miss the first time and than hit every time after that. I was looking at the code in rails / activesupport / lib / active_support / cache.rb and noticed on line 141 there is the following if statement:
if !options[:force] && value = read(key, options)
value is set to false in the if statement, causing the condition to fail and miss. It would be better if value was read after the if statement and the if statement would be changed to
if !options[:force] && exist?(key)
Comments and changes to this ticket
-
-
Thijs de Vries January 31st, 2009 @ 11:34 PM
That last patch I sent caused some of the tests to fail. This one won't fail any tests and allows for the new ones to pass.
-
DHH February 5th, 2009 @ 08:01 PM
Won't this lead to a race condition? You have two calls to the separate cache to check for the same key. The key could have come and gone in between those two calls.
-
Derek McLoughlin March 12th, 2009 @ 03:01 PM
Would it be better to have the following:
if !options[:force] && ((value = read(key, options)) != nil) -
Thijs de Vries March 12th, 2009 @ 03:10 PM
- Tag cleared.
@@@ruby if !options[:force] && ((value = read(key, options)) != nil)
won't let you store nil as a value. In case a really expensive function returns nil, one may still wanna store nil so they don't have to run the really expensive function again. Probably have to work with thread locks to make this work. -
Derek McLoughlin March 13th, 2009 @ 04:17 PM
True, but nil is currently being used as meaning "the thing isn't in the cache". The above solution works for cached values of 'false'.
-
MatthewRudy November 28th, 2009 @ 06:09 PM
- Assigned user set to “José Valim”
- Tag set to “activesupport, cache, false, fetch”
hey,
what happened to this?The "false" case of this bit me and a colleague again this week.
Spent ages wondering why using memcache was even slower than hitting our DB.So here is a patch, just to deal with the "false" case.
But I feel that there should be a more clever way to deal with a nil store.
Anyway,
here is my patch.http://github.com/matthewrudy/rude-rails/commit/37d50e8e4d4eec27e06...
-
José Valim November 28th, 2009 @ 10:17 PM
- Assigned user cleared.
-
-
MatthewRudy March 2nd, 2010 @ 03:59 AM
my patch still works
http://github.com/matthewrudy/rude-rails/commit/6cb522c735d8fa9895b...and I upped the patch
but now its a bit weird
(I think because of the rebase) -
-
W. Andrew Loe III June 16th, 2010 @ 09:16 PM
Chris Kampmeier in #3482 appears to have come up with a patch that does not introduce a race condition.
-
Santiago Pastorino February 2nd, 2011 @ 04:37 PM
- State changed from “new” to “open”
- Importance changed from “” to “”
This issue has been automatically marked as stale because it has not been commented on for at least three months.
The resources of the Rails core team are limited, and so we are asking for your help. If you can still reproduce this error on the 3-0-stable branch or on master, please reply with all of the information you have about it and add "[state:open]" to your comment. This will reopen the ticket for review. Likewise, if you feel that this is a very important feature for Rails to include, please reply with your explanation so we can consider it.
Thank you for all your contributions, and we hope you will understand this step to focus our efforts where they are most helpful.
-
Santiago Pastorino February 2nd, 2011 @ 04:37 PM
- State changed from “open” to “stale”
Create your profile
Help contribute to this project by taking a few moments to create your personal profile. Create your profile »
<h2 style="font-size: 14px">Tickets have moved to Github</h2>
The new ticket tracker is available at <a href="https://github.com/rails/rails/issues">https://github.com/rails/rails/issues</a>
José Valim
MatthewRudy
Nikos Dimitrakopoulos
Thijs de Vries