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From Jedediah Smith <>
Subject Re: View with incremental counter
Date Tue, 18 Nov 2008 19:30:29 GMT

Grasping the concepts involved in map/reduce might end up being a 
significant hurdle to CouchDB adoption so I would encourage features 
that assist in that regard. Sandboxing might also be necessary to 
enforce whatever is ultimately CouchDB's security model.

Spidermonkey must have sandboxing capabilities if it runs the javascript 
for both the Firefox browser and the web pages it loads.

Paul's case of caching large objects is something to consider (and a 
reason my previous email was not strictly correct) but could perhaps be 
handled more formally or left to custom view servers.

Benjamin Nortier 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
> <> 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

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