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memcachedenyim

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

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?

Solution

  • 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.