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Date: Thu, 11 Nov 2010 20:06:59 -0500
Message-ID: <AANLkTinda8VQqH967VQDYV2CrPZ=miDGcvxEBemUVP1t@mail.gmail.com>
Subject: Re: First doc in a group?
From: Chad George <chad@mgproducts.com>
To: user@couchdb.apache.org
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After a little reflection, maybe my original response was a little too
strong. You might need to use a reduce if you want the latest document for a
whole set of users in a single call.

If you only wanted the latest document for a single user, then the view+key
ranges+limit=1  is definitely the best approach.

Maybe Cory's idea is the best approach. A reduce function that calculates
the latest document (maximum timestamp) and also use group=True or
group_level=1 (depending on the final view key structure used)

-Chad

On Thu, Nov 11, 2010 at 6:29 PM, Mike Bannister <mikebannister@gmail.com>wrote:

> Cool, I understand now reduce isn't right, initially posted to the list
> because I couldn't decide that on my own.
>
> So what's the most efficient way to get the latest document for each user?
> Seems like I shouldn't have to do one query per user but I'm open minded (:
>
> -Mike
>
>
>
> On Thu, Nov 11, 2010 at 5:52 PM, Chad George <chad@mgproducts.com> wrote:
>
> > Selecting one row in a view out of many possible isn't what reduce is
> for.
> >
> > I try not to think of it as reducing a set of view results to a smaller
> set
> > but rather reducing each and every entry in the view to something
> smaller.
> >
> > The fact that reduce gets multiple view rows to work on at once is just
> an
> > optimization. I think its better to think of reduce as working on exactly
> > one view row at a time then rereduce the result to get final answer.
> > On Nov 11, 2010 5:22 PM, "Mike Bannister" <mikebannister@gmail.com>
> wrote:
> > > Cory, cool thanks. Wasn't able to decide on my own if reducing was OK
> for
> > > this kind of thing.
> > >
> > > Robert, but I need one document for each user, wouldn't that be a
> summary
> > of
> > > sorts?
> > >
> > > -Mike
> > >
> > >
> > > On Nov 11, 2010 4:46 PM, "Cory Zue" <czue@dimagi.com> wrote:
> > >
> > > You could emit the users as keys, and in your reduce function just
> > > return the latest by date.
> > >
> > >
> > > On Thu, Nov 11, 2010 at 4:35 PM, Mike Bannister <
> mikebannister@gmail.com
> > >
> > > wrote:
> > >> Yeah, I'm trying...
> >
>

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