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From Norman Barker <>
Subject Re: couchdb on 8 core redhat/fedora
Date Mon, 10 Aug 2009 15:46:27 GMT

a post-write filter is to change the response from a call to update,
where as a _show is for generating a particular response.  I was
wondering about being able to add interceptor handlers (filters in the
servlet world).

The pmap example was nice, but as you have commented writes are
serialized so I will start again! I will look at seeing if I can
parallize the json parsing.


On Mon, Aug 10, 2009 at 8:00 AM, Paul Davis<> wrote:
> On Mon, Aug 10, 2009 at 9:53 AM, Norman Barker<> wrote:
>> I was a little surprised by this, and did a quick grep on spawn on the
>> couchdb code base, it isn't used that much and I wonder why. In
>> particular for bulk doc updates I wonder why pmap isn't used (perhaps
>> I am missing something), for my project I have needed to write a
>> custom updater, a pre-writer, (great modular design now btw in 0.9 I
>> was able to hook it all up - updater, query server from the ini file)
>> and I am going up to a javascript function to parse an incoming
>> document (not JSON) into multiple JSON documents I am then using a
>> pmap to write this to the db, doesn't seem to be that complicated and
>> I should then get an increase in speed to compensate for the initial
>> javascript parsing delay.
>> Could all (or most) use of the plain map be replaced with a pmap in
>> couchdb or am I missing something?
>> Not to hijack this thread, but I have written a pre-writer, are there
>> any plans to add filters (pre and post) on the couchdb roadmap?
>> As a J2EE developer, I still see the benefit of the Erlang VM - easier
>> to develop 'fast' applications in for sure.
>> thanks,
>> Norman
> Couple points,
> All writes to disk are serialized, so using a pmap to save docs isn't
> going to save you much unless you're parallelizing the JSON parsing.
> I'm not sure what you mean by pre and post filters. I wrote a first
> pass at being able to mutate documents when saving last week or so.
> Post filters sounds alot like _show.
> HTH,
> Paul Davis

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