Is it possible to get/search Memcached keys by a prefix?

memcached enyim
Zanoni picture Zanoni · Feb 3, 2011 · Viewed 25.5k times · Source

I'm writing to memcached a lot of key/value -> PREFIX_KEY1, PREFIX_KEY2, PREFIX_KEY3

I need to get all the keys that starts with PREFIX_

Is it possible?

Answer

btilly picture btilly · Feb 3, 2011

Sorry, but no. Memcached uses a hashing algorithm that distributes keys at apparently random places, and so those keys are scattered all over. You'd have to scan everything to find them.

Also you should be aware that, by design, memcached can drop any any key at any time for any reason. If you're putting stuff in, you should be aware that you can't depend on it coming back out. This is absolutely fine for its original use case, a cache to reduce hits on a database. But it can be a severe problem if you want to do something more complicated with it.

If these limitations are a problem, I would suggest that you use Redis instead. It behaves a lot like memcached, except that it will persist data and it lets you store complex data structures. So for your use case you can store a hash in Redis, then pull the whole hash out later.

Related questions

Memcached vs. Redis?

We're using a Ruby web-app with Redis server for caching. Is there a point to test Memcached instead? What will give us better performance? Any pros or cons between Redis and Memcached? Points to consider: Read/write speed. Memory usage. …

Read More
How to stop and restart memcached server?

How to stop and restart memcached server 1.4.5 in linux OS from command line?

Read More
configure: error: C compiler cannot create executables

I've checked a number of similar questions on stackoverflow but haven't found an answer yet. I'm trying to install memcached on Lion OSX as shown here. Here's what I'm getting: j-court-demones-macbook-pro:libevent-1.4.12-stable jcourtdemone$ ./configure; make checking for a BSD-compatible …

Read More