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

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.


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