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From Damien Katz <>
Subject Re: filter for _changes
Date Mon, 20 Jul 2009 18:53:05 GMT
Good work Chris. I went ahead and made the optimization so it only  
uses the os process while actively filtering changes.

My only suggestion is to change the "filters" field to  
"changes_filters", so it's a little more clear what its filtering.

Also, I think it would be cool to be able to pass params to the filter  
functions too, either through the query string or via POST. For  
example in the demos, to allow users to subscribe to any number of  
channels in chat, or just get changes on the displayed month in the  


On Jul 20, 2009, at 1:17 AM, Chris Anderson wrote:

> Devs,
> I've just committed a patch (r795687) that adds the ability to filter
> _changes requests with a JavaScript function.
> The function signature is:
> function(doc, req, userCtx) {
>  return (true or false);
> }
> When it returns true (or something truthy, like a non-empty string or
> a non-zero number), the change is passed along to the user, otherwise
> it is skipped.
> The filter functions are stored on design documents under the
> "filters" field. The current best source of documentation is the
> changes.js test.
> To query changes with a filter, the syntax is like:
> GET /db/_changes?filter=ddocname/filtername
> The biggest problem with this patch is that it uses a JavaScript OS
> process per connected filtered listener. Fixing this is an
> optimization as it won't effect the API, which is why I'm comfortable
> committing this.
> I'd appreciate some review to make sure the implementation is on the
> right track.
> Cheers,
> Chris
> -- 
> Chris Anderson

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