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From Chris Anderson <>
Subject Re: couchdb on 8 core redhat/fedora
Date Mon, 10 Aug 2009 19:32:17 GMT
On Mon, Aug 10, 2009 at 8:55 AM, Paul Davis<> wrote:
> On Mon, Aug 10, 2009 at 11:46 AM, Norman Barker<> wrote:
>> Paul,
>> 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).
> Oh. As part of the _update work there was a feature request to return
> an arbitrary response. Not sure if that'll make the first
> implementation or not.

yep, patch is under way, it supports updating the doc and returning an
arbitrary response. in progress code for _update is here:

I'll post to dev@ when it's ready for review

>> 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.
> If you're building from source, try something like:
> ./bootstrap && ERLC_FLAGS=+native ./configure && make dev &&
> That should give you a nice JSON performance boost assuming your
> Erlang is HiPE enabled. It'll just complain and build without if its
> not.
> HTH,
> Paul Davis
>> Norman
>> On Mon, Aug 10, 2009 at 8:00 AM, Paul Davis<> wrote:
>>> On Mon, Aug 10, 2009 at 9:53 AM, Norman Barker<>
>>>> 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

Chris Anderson

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