On 26.10.2008 19:05 Uhr, Roché Compaan wrote:
On Sun, 2008-10-26 at 18:50 +0100, Andreas Jung wrote:
On 26.10.2008 18:43 Uhr, Roché Compaan wrote:
On Sat, 2008-10-25 at 09:20 +0200, Hedley Roos wrote:
I suspect specific indexes are just performing suboptimally and needs to
be improved. ExtendPathIndex in Plone seems to be one of them.
Path indexes and fulltext indexes have a much more complicated
implementation compared to field or keyword indexes.
I know, and this alone makes a good argument for caching at catalog
level. In our case we used membrane, which makes an excessive amount of
catalog queries when looking up users so some level of caching was
essential.
First caching is good thing :-)
But how about the following issue: CMF/Plone inject additional
subqueries for expires/effective/typesAndRoles. At least the security
related aubqueries make a cached catalog result very specific to a
particular user. That seems to be very ok for a site with lots of
anonymous users - it might be an issue with lots of authenticated users.
It might be necessary to add some kind of intelligence to decide what to
cache and what not. I don't think it does not make sense to cache the
result of a fulltext search. I am just thinking if it would make sense
to cache on the index level instead of catalog level? So you could for
example cache "expensive" index queries (path index) and combine them
with uncached index which are supposed to be fast..however
such decisions require detailed mesurements on real systems.
One other thing concerning memcached: there is obviously a limit to 1MB
for data you can store as a value. We have not found an obvious way for
increasing this limit other by patching the memcached sources. We came
up with an implementation where data >1MB is split up into individual
junks (we have a dedicated set_huge(), get_huge()) implementation.
Andreas
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