Feedback on Tag Support

dormando dormando at
Fri May 9 18:09:25 UTC 2008

Shoot; All of the items that were tagged by that tag. Which could be a 
million if you're using tags instead of namespaces.

dormando wrote:
> On skimming the code it looks like tag invalidating loops over all items 
> and removes them from a linked list, then removes the tag from the splay 
> tree.
> -Dormando
> Jonathan Ariel wrote:
>> It doesn't seems to be a loop, it says "We use hash and splay tree, 
>> make the tag_add and tag_delete commands very quickly, and save memory 
>> as much as possible."
>> On Fri, May 9, 2008 at 2:44 PM, Dustin Sallings <dustin at 
>> <mailto:dustin at>> wrote:
>>     On May 9, 2008, at 9:52, John Kramlich wrote:
>>>     Is anyone using the variant of memcached v 1.2.4 that supports
>>>     tagging found at the following
>>>     URL ?  I am in the planning
>>>     stages of major feature additions to my web application and would
>>>     really like to use this version.  I'm looking for feedback from
>>>     others who have used it.  Is it stable enough for production use?
>>>      Any issues?
>>     I think tagging is a generally useful feature, but we honestly
>>     haven't put a lot of effort into reviewing the tag code.
>>     In particular, we want tagging to be cheap on both setting and
>>     invalidating.  If either operation has to perform more than a single
>>     lookup, then it may not be desirable.  In particular, deleting by
>>     tag is a loop (within a lock and with another nested loop within
>>     it), which may cause the server to hang for long periods of time
>>     when invalidating a widely-used tag.  It *should* be possible to do
>>     this without such a loop.
>>     --     Dustin Sallings

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