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From Scott Shumaker <sshuma...@gmail.com>
Subject Re: View Performance (was Re: The 1.0 Thread)
Date Thu, 02 Jul 2009 23:17:39 GMT
I'll try that out tomorrow and post the results here.

On Thu, Jul 2, 2009 at 3:01 PM, Paul Davis<paul.joseph.davis@gmail.com> wrote:
> On Thu, Jul 2, 2009 at 5:50 PM, Scott Shumaker<sshumaker@gmail.com> wrote:
>> One question, though: Why are the emitted view results stored as
>> erlang terms, as opposed to storing the JSON returned from the view
>> server - which is what you'll be serving to the clients anyway?
>>
>> If you skipped the reverse json->erlang encoding, and additionally
>> stored a cached json copy of each document alongside the document
>> whenever a document in couchdb was created/updated (which you could
>> incrementally generate in a separate erlang process so you don't have
>> to slow down write performance) - and just pass this json copy to the
>> view, you could basically eliminate the json->erlang conversion
>> overhead entirely (since it would only be done asynchronously).
>>
>> Even if you need to store the emitted view results back into erlang,
>> you could have a special optimization case for emitting (key, doc) -
>> because you already have the document as both erlang/json (assuming
>> you were storing cached json copies).  And include_docs would get
>> faster since you wouldn't need to do the json conversion there either.
>>
>> Just a thought.
>>
>
> Premature optimization is the root of all evil? Have you tried
> compiling CouchDB with HiPE enabled. I'm inclined to agree with you
> that the large JSON values are probably a significant cause here.
> Assuming your Erlang is HiPE enabled you can do something like this to
> compile CouchDB:
>
>    $ ./bootstrap
>    $ ERLC_FLAGS="+native +inline +inline_list_funcs" ./configure
>    $ make
>    $ sudo make install
>
>
>> Scott
>>
>> On Thu, Jul 2, 2009 at 2:42 PM, Scott Shumaker<sshumaker@gmail.com> wrote:
>>> I should mention that we tend to emit (doc._id, doc) in our views - as
>>> opposed to doc._id, null and using include_docs - because we found
>>> that doc._id,null gave us a 30% speedup on building the views, but
>>> cost us about the same on each additional hit to the view.
>>>
>>> Scott
>>>
>>> On Thu, Jul 2, 2009 at 2:15 PM, Scott Shumaker<sshumaker@gmail.com> wrote:
>>>> We see times that are considerably worse.  We mostly have maps - very
>>>> few reduces.  We have 40k objects, about 25 design docs, and 90 views.
>>>>  Although we're about to change the code to auto-generate the design
>>>> docs based on the view filters used (re: view filter patch) - see if
>>>> that helps.
>>>>
>>>> Maybe it's because we have larger objects - but re-indexing a typical
>>>> new view takes > 5 minutes (with view filtering off).  Some are worse.
>>>>  With view filtering on some can be quite fast - some views finish in
>>>> like 10 seconds.  Interestingly, reindexing all views takes about an
>>>> hour - with or without view filtering.  I'm guessing that a
>>>> substantial part of the bottleneck is erlang -> json serialization.
>>>> Many of our objects are heavily nested structures and exceed 10k in
>>>> size.  One other note - when we tried dropping in the optimized
>>>> 'main.js' posted on the mailing list, we saw an overall 20% speedup.
>>>> Unfortunately, it wasn't compatible with the authentication stuff, and
>>>> the deployment was a bit wacky, so we're holding off on that right
>>>> now.
>>>>
>>>>
>>>> On Thu, Jul 2, 2009 at 11:30 AM, Damien Katz<damien@apache.org> wrote:
>>>>>
>>>>> On Jul 2, 2009, at 1:55 PM, Paul Davis wrote:
>>>>>
>>>>>> On Thu, Jul 2, 2009 at 1:29 PM, Damien Katz<damien@apache.org>
wrote:
>>>>>>>
>>>>>>> On Jul 2, 2009, at 1:16 PM, Jason Davies wrote:
>>>>>>>
>>>>>>>> On 2 Jul 2009, at 15:38, Brian Candler wrote:
>>>>>>>>
>>>>>>>>> For some fruit that was so low-hanging that I nearly
stubbed my toe on
>>>>>>>>> it,
>>>>>>>>> see https://issues.apache.org/jira/browse/COUCHDB-399
>>>>>>>>
>>>>>>>>
>>>>>>>> Nice work!  I'd be interested to see what kind of performance
increase
>>>>>>>> we
>>>>>>>> get from Spidermonkey 1.8.1, which comes with native JSON
>>>>>>>> parsing/encoding.
>>>>>>>>  See here for details:
>>>>>>>> https://developer.mozilla.org/En/Using_native_JSON .
>>>>>>>>
>>>>>>>> Rumour has it 1.8.1 will be released any time soon (TM)
>>>>>>>
>>>>>>> I'm not sure the new engine is such a no-brainer. One thing about
the new
>>>>>>> generation of JS VMs is we've seen greatly increased memory usage
with
>>>>>>> earlier versions. Also the startup times might be longer, or
shorter.
>>>>>>>
>>>>>>> Though I wonder if this can be improved by forking a JS process
rather
>>>>>>> than
>>>>>>> spawning a new process.
>>>>>>>
>>>>>>
>>>>>> Memory usage is a definite concern. I'm not sure I follow why startup
>>>>>> times would be important though. Am I missing something?
>>>>>
>>>>> Start up time isn't a huge concern, but it's is a something to consider.
On
>>>>> a heavily loaded system, scripts that normally work might start to time
out,
>>>>> requiring restarting the process. Lots of restarts may start to eat lots
cpu
>>>>> and memory IO.
>>>>>
>>>>> -Damien
>>>>>
>>>>>
>>>>>>
>>>>>>> -Damien
>>>>>>>
>>>>>>>> --
>>>>>>>> Jason Davies
>>>>>>>>
>>>>>>>> www.jasondavies.com
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>
>>>>>
>>>>
>>>
>>
>

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