[Zope-dev] Re: Caching ZCatalog results

[Tres Seaver]

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Roché Compaan wrote:
> On Fri, 2007-02-23 at 06:55 -0500, Tres Seaver wrote:
>> Roché Compaan wrote:
>>> I'm curious, has anybody played around with the idea of caching ZCatalog
>>> results and if I submitted a patch to do this would it be excepted?
>>>
>>> I quickly coded some basic caching of results on a volatile attribute
>>> and I was really surprised with the amount of cache hits I got
>>> (especially with a Plone site that is a heavy user of the catalog)
>> +1.  I think using the 'ZCachable' stuff (e.g., adding a RAMCacheManager
>> and associating a catalog to it) would be the sanest path here.
> 
> Cool idea. I haven't done any coding involving OFS.Cache though. Looking
> at it briefly it looks like one can modify the catalog to subclass
> OFS.Cacheable and then use the ZCacheable_get, ZCacheable_set and
> ZCacheable_invalidate methods to interact with a cache manager. This
> needs to be pretty explicit though. Are there any side effects that I
> should guard against if the catalog subclasses OFS.Cache?

I don't think so.  Here are some random thoughts on the idea:

 -  The 'searchResults' method must pass its keyword arguments as
    part of the cache key.

 - I don't know if there is a reasonable way to do 'mtime' for
   the catalog:  we would like to be able to get an mtime cheaply
   for the BTrees (indexes, the 'data' container), but I don't know
   if that is possible.

 - The "right" place to do this feels like the 'searchResults' of
   ZCatalog, just before it calls 'self._catalog.searchResults'.

 - The CMF's catalog overrides 'searchResults', but calls it at
   the end, so everything there should work.


Tres.
- --
===================================================================
Tres Seaver          +1 540-429-0999          tseaver at palladion.com
Palladion Software   "Excellence by Design"    http://palladion.com
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