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From James Marca <jma...@translab.its.uci.edu>
Subject Re: unexpected behavior in view generation
Date Tue, 29 Sep 2009 17:33:20 GMT
On Mon, Sep 28, 2009 at 05:20:56PM -0400, Paul Davis wrote:
> On Mon, Sep 28, 2009 at 5:10 PM, James Marca
> <jmarca@translab.its.uci.edu> wrote:
> > Hi All,
> >
> > I ran across some behavior this weekend that I didn't expect.
> >
> > I have a lot of data, and I'm trialing storing the raw data in
> > CouchDB.  I have 12 databases (manually "sharded" by month), each with
> > about 115,000,000 documents, and an average size of about 25G.  I
> > created a view index for each database, and was updating away, when I
> > noticed a typo in the October database.  I corrected the typo (in
> > Futon), reloaded the view page (again in futon), and *assumed* that
> > the old view indexing job was killed and restarted with the new code.
> > In fact, what happened was that the old, incorrect index job kept
> > running (for 48 hours) and when it finished, it restarted.
> >
> > Is this a minor bug, or did I miss an option somewhere?
> >
> 
> I'd call it a bad inconvenience for large data sets. Technically what
> happened was that it went through and indexed all of your data with
> the bad version, then the last edit was your change to the design doc,
> which reset the indexes and started things over which is the intended
> behavior.
> 
> Just using my brain debugger it seems like it should be fairly easy to
> crash (Erlang speak for 'shutdown gracefully') any running update
> processes. Feel free to create a ticket in JIRA for the feature. Put a
> note on it that it'd be good for anyone wanting to learn the view
> update engine code as all of that would be mostly towards the top of
> the stack.

Thanks for the reply and explanation.

I'll add "post a jira ticket" to today's todo list.  

> 
> > (The machine I am running this on is running version 0.9.0.  I will
> > test something similar in the near future on 0.9.1 machine.)
> >
> 
> Everything all the way up to trunk will behave the same way as 0.9.0.
> 
> > On the plus side, Erlang and CouchDB happily cranked away both loading
> > the data and then building the views on my 8-core machine, using up
> > lots of the available processor resources (instead of just max-ing out
> > one core).  I still wish I could spawn multiple threads per index job,
> > but since there's no way I could write that code, I'll wait.
> >
> 
> The view indexer in trunk will now split view updates over two cores
> and is faster than 0.9's indexer. I'm uncertain if this work was back
> ported to 0.10 or not.

Cool, I just downloaded trunk today and will try it out.  I'm also
going to experiment with the couchdb-lounge project.


Regards,
James Marca


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