Clear section of cache

[tylercollier]

I'd like to clear a section of my cache. Say for example that I store data by prefixing it with a namespace. Perhaps I cache some twitter data, facebook data, etc. I might store them as twitter.myvalue1, twitter.myvalue2, and facebook.myvalue1, facebook.myvalue2. How could I delete the cache entries for twitter? And I don't know all the names of the values. It's not necessary myvalue1/2/3/etc, I just know it starts with twitter.

[spud]

[Edit: 22 July 2015 to fix inconsistency in variable names, for clarity]

I was trying to figure out the same problem...

I cache individual pages, for example, but I also cache "chunks" of data based on what module they belong to. And sometimes I'd like to clear the cache of any data that belongs to a certain module.

Some individual caches allow you to "group" cache items like this, but for flexibility with a generic caching system, you have to be a bit more creative.

In my case, I kept a second cache, whose key was a consistent module identifier (e.g. "cache.twitter"), and each value in the cache corresponded to another cache key.

So I would, for example,

// Save a twitter module value:
twitter.myvalue1 = "foo";
// Save the key name in another array that holds all the "twitter" module cache keys
cache.twitter = "twitter.myvalue1";

// ..and repeat, adding the new key to the existing array of "twitter" keys
twitter.myvalue2 = "bar";
cache.twitter = "twitter.myvalue1,twitter.myvalue2"; // this would probably be an array, not a list

// ..and repeat, adding the new key to the existing array of "twitter" keys
twitter.myvalue3 = "baz";
cache.twitter = "twitter.myvalue1,twitter.myvalue2,twitter.myvalue3"

Now, when you want to clear the entire "twitter" cache, you do this (in pseudo-code)

$keys = $Cache->get("cache.twitter");
foreach($keys as $key) {
$Cache->delete($key);
}
// And delete the cache item that held all the keys
$Cache->delete("cache.twitter");

If you write simple functions to encapsulate this functionality, it's pretty flexible and easy to integrate.

spud.

On Oct 13, 2014, at 2:50 PM, tylercollier wrote:

I'd like to clear a section of my cache. Say for example that I store data by prefixing it with a namespace. Perhaps I cache some twitter data, facebook data, etc. I might store them astwitter.myvalue1, twitter.myvalue2, and facebook.myvalue1, facebook.myvalue2. How could I delete the cache entries for twitter? And I don't know all the names of the values. It's not necessary myvalue1/2/3/etc, I just know it starts with twitter.

[tylercollier]

Great idea. I just implemented your idea and it works great.

I ended up using the term tag instead of module, because like gmail tags, I might want to tag a cache value with multiple tags. If I only ever wanted to assign a value to a particular module, I think that could be accomplished with the 'securityKey' (which only works for files and PDO drivers; I'm using the files driver) concept already present in phpfastcache.

[tylercollier]

I have not yet tested this in the real world. I'm nervous about how long $cache->delete() calls will take in a loop with many keys. I'll report back after I get some real world testing.

[rajneeshojha]

were you able to implement this group cache?

[tylercollier]

@rajneeshojha: yes. I did it just like spud suggested. It was very simple. It's in my own code, not part of the phpfastcache library, so I did not do a pull request or anything.

[rajneeshojha]

can you please share the code? Regards
Rajneesh Ojha

 On Thursday, July 23, 2015 2:51 AM, Tyler Collier <notifications@github.com> wrote:

@rajneeshojha: yes. I did it just like spud suggested. It was very simple. It's in my own code, not part of the phpfastcache library, so I did not do a pull request or anything.—
Reply to this email directly or view it on GitHub.

[tylercollier]

See code here: https://github.com/khoaofgod/phpfastcache/issues/59#issuecomment-58953860