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Message-ID: <d6f4831c0811180726i53135ed1n69a9f74c8f1f4caf@mail.gmail.com>
Date: Tue, 18 Nov 2008 15:26:49 +0000
From: "Benjamin Nortier" <bjnortier@gmail.com>
To: couchdb-user@incubator.apache.org
Subject: Re: View with incremental counter
In-Reply-To: <e2111bbb0811180659n7ddda0feq75788dfd4e045422@mail.gmail.com>
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References: <a95d32b00811180427n4b41c757xe8b2390a5a7428d1@mail.gmail.com>
	 <4922C646.7010802@silencegreys.com>
	 <d6f4831c0811180651i5e6560eeqfffb97c817803042@mail.gmail.com>
	 <e2111bbb0811180659n7ddda0feq75788dfd4e045422@mail.gmail.com>

I would imagine that it's not very easy if you want to retain the
ability to instantiate objects outside the function.

But I'm no expert :)

Ben

On Tue, Nov 18, 2008 at 2:59 PM, Paul Davis <paul.joseph.davis@gmail.com> wrote:
> If this is easy and you see an implementation, I think it'd be a great
> addition to force the sand boxing of individual functions.
>
> That said, I don't know much about the JS internals so I'm not sure
> how hard it would be to auto detect what might cause side effects
> outside the function and what wouldn't. I've stuck largish objects
> outside the function itself on the assumption that they'll only be
> instantiated once as opposed to once per document.
>
> I have absolutely no idea if that's even necessary though.
>
> Paul
>
> On Tue, Nov 18, 2008 at 9:51 AM, Benjamin Nortier <bjnortier@gmail.com> wrote:
>> Should CouchDB not restrict defining state outside the map function?
>> I.e. you should not be able to declare a counter outside the function?
>>
>> On Tue, Nov 18, 2008 at 1:42 PM, Jedediah Smith
>> <jedediah@silencegreys.com> wrote:
>>>
>>> You can't maintain a state across calls to map functions in this way. Map
>>> functions can be called in any order or in parallel, any number of times on
>>> a particular document and in completely separate environments. They should
>>> not have any side effects or depend on any outside state.
>>>
>>> You should read up on Google's MapReduce and maybe functional programming in
>>> general in order to understand how CouchDB works.
>>>
>>> If you just want to number the results of your view, that can be easily done
>>> by the calling code.
>>>
>>> Adam Groves wrote:
>>>>
>>>> Hi,
>>>>
>>>> I've got the following view:
>>>>
>>>> count = 0;
>>>> function(doc) {
>>>>  if(doc.type == "document") {
>>>>    count = count + 1
>>>>    emit(doc._id, count);
>>>>  }
>>>> }
>>>>
>>>> The idea is that I get a list of documents, each having a counter
>>>> value which is incremental. I expected the count values to come out in
>>>> order, but that isn't the case: my first few documents have values of
>>>> 62, 61, 22, 19. I'm not quite sure what's going on here - any ideas
>>>> how the order is being set here?
>>>>
>>>> Regards
>>>>
>>>> Adam Groves
>>>>
>>>
>>
>>
>>
>> --
>> Benjamin Nortier
>> e: bjnortier@gmail.com
>> c: +44 (0)778 946 1959
>> msn: bjnortier@mail.com
>> gtalk: bjnortier@gmail.com
>>
>


-- 
Benjamin Nortier
e: bjnortier@gmail.com
c: +44 (0)778 946 1959
msn: bjnortier@mail.com
gtalk: bjnortier@gmail.com