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Re: (ITS#5756) 2.4 slapo-pcache only caches first lookup for certain templates
On 4 Nov 2008, at 09:26, Pierangelo Masarati wrote:
> email@example.com wrote:
>> Hi there, is there any further debugging I could usefully carry
>> out for this issue, or does it need someone who understands the
>> code a bit better?
> It's not a debugging problem, but rather a design issue. The
> current design makes use of the first AVA of the filter to decide
> how two filters are compared. In your case, the first component is
> common to all filters, so only the first occurrence of a search with
> that template can be cached. This fact, to my knowledge, is
> undocumented, but there's little to do except redesign this weighing
> criterium. As I already pointed out, you need to make the most
> significant filter AVA appear first in your filter template. Unless
> anyone voluteers for a complete redesign [*] of this portion of
> slapo-pcache(5), I take your ITS as a request to document this
> aspect of template design.
> [*] a complete redesign could also get rid of strict ordering of
> filter AVAs, allow "static" portions of the filter (something like
> (&(objectClass=person)(uid=)) and so) and other relatively
> unfriendly aspects of slapo-pcache(5) configuration.
The problem with changing the ordering in the template is that it then
doesn't match the real lookups that occur and so the entries aren't
cached - this is something over which I have no control - e.g. queries
generated by 'ls -l', or by somebody logging into the machine, etc,
etc. This is why we have the filters this way.
e.g. sshing into one of our scientific linux 5.2 hosts generates the
[sybies]toby: grep 'query template' ~/tmp/pcache-login |cut -d' ' -f13|
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