Delete Objects based on REGEX.
jan at hitflip.de
Thu Jul 26 08:55:49 UTC 2007
You wouldn't be able to delete all keys tagged "xxx_whiffelbat_abc". You
would only be able to delete all keys tagged "whifflebat". If you need
to be able to delete all keys related to whifflebat, you need to tag
them with it.
So yes, it does require a bit more planning. But since tagging a key
scales you can merrily tag away.
> How do tags help when a developer runs over, saying something about
> expiring all keys with the word 'whifflebat' in the middle?
> Or, I guess, is the idea of tagging more about not using key prefixing
> at all anymore? That'd be swell, but I think that would be the two camps
> of thought here.
> Tags) Requires planning
> Regex) Pragmatism
> Maybe there's a way to do both without duplicating tons of code? :)
> Steven Grimm wrote:
>> I actually implemented regex deletes quite some time back. But the
>> problem is that I did it in a brute-force way, nothing elegant or
>> efficient, and if you have a large cache the whole thing will freeze up
>> for many seconds, chewing 100% of your CPU while the code walks through
>> all the items comparing them against the regex. We wanted it for very
>> occasional administrative operations where the cache freezing up for a
>> short while would be less disruptive than a full flush, but I think
>> we've used it maybe two or three times at most because it's so nasty.
>> Brad's generation-based idea makes much more sense as a long-term
>> approach to this feature, but honestly I like tags a lot better. I'd
>> rate tags a 10 and regex deletes, even well-implemented ones, at most a
>> 6 or 7 because they're so inflexible and require that all consumers of
>> objects in the cache be aware of all the metadata you can use to address
>> a particular object (because it's all part of the key and you need the
>> whole key to query the cache.) Tags are IMO far superior because you can
>> tag an item with metadata that some of your clients are blissfully
>> unaware of.
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> End of memcached Digest, Vol 36, Issue 55
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