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From Murray Altheim <>
Subject Re: Priha
Date Sun, 05 Oct 2008 10:55:22 GMT
Janne Jalkanen wrote:
>> I'm curious to know why this might be, e.g., would this be true on
>> a RieserFS linux machine? Is this limitation based on the OS or on
>> the Priha implementation? If the latter, why? (I'd like to avoid
>> the same issues if I were to build a Berkeley DB backend).
> This is actually a discussion better suited on the priha-dev mailing 
> list :-).

Point taken. :-)

> Anyhoo, the reason why it does not currently scale is the fact that UUID 
> mappings are O(N) (or might be O(N^2), haven't checked) because of a 
> simplistic implementation.  This is not a problem for the current JDBC 
> implementation, because it stores UUIDs with the nodes themselves (and 
> therefore can be fetched with a simple JOIN).  With an index it's 
> essentially an O(log N) op.

If it's an ID issue and you don't *need* UUID I've got an implementation
of an ID generator that can pop up unique IDs at about 1/5ms speed on a
typical laptop, and (within the realm of reason) would be globally unique
as well. I haven't had a chance to look into the code so I may be barking
up the wrong tree here but I thought I'd mention it.

> The FileProvider impl is fixable, once I (or someone else) starts 
> thinking about it.  Optimizing something like this is going to be pretty 
> cool ;-).  My stats are currently showing that 99% of the performance is 
> in the storage layer, but the tests are quite simplistic.  But working 
> on this is quite a different beast from JSPWiki, where you need to 
> understand quite a lot of code to help - for Priha, you can start 
> working on really small bits and have a huge impact in the performance.

Sounds like fun. Like I mentioned I'll hopefully know this week what my
availability will be for this (otherwise it'd be on my own time).


Murray Altheim <murray07 at>                           ===  = =                                     = =  ===
SGML Grease Monkey, Banjo Player, Wantanabe Zen Monk               = =  = =

       Boundless wind and moon - the eye within eyes,
       Inexhaustible heaven and earth - the light beyond light,
       The willow dark, the flower bright - ten thousand houses,
       Knock at any door - there's one who will respond.
                                       -- The Blue Cliff Record

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