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Date: Sun, 5 Jul 2009 15:18:33 -0500
Message-ID: <26650b020907051318n7eedd29ehad9decdb2c0240f6@mail.gmail.com>
Subject: Re: getting unique set of document id's
From: Ross Bates <rbates@gmail.com>
To: user@couchdb.apache.org
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Hi Paul - thank you for the pointers. Something I'm unclear on though...
using a sum in the reduce returns something like this for all the tags:

foo, 3
bar, 5
baz, 7

When I use the multi-key fetch against the view it doesn't return specific
docid's for each tag, just a subset of tags and their counts.

POST {"keys": ["foo", "bar"]}

foo, 3
bar, 5

How can I get access to the list of docid's which make up the total?


On Sat, Jul 4, 2009 at 3:52 PM, Paul Davis <paul.joseph.davis@gmail.com>wrote:

> On Sat, Jul 4, 2009 at 2:48 PM, Ross Bates<rbates@gmail.com> wrote:
> > Hi All - finally got up an running with 0.9.0 and have been experimenting
> > with the POST {"keys": ["key1", "key2", ...]} feature and have a question
> >
> > Take the typical example of a set of blog posts which can be tagged with
> > 1...n tags. Pretend I want to find all posts tagged with both "foo" and
> > "bar".
> >
> > A simple map would look something like this
> >
> > function(doc) {
> >  for(i in doc.tags) {
> >      emit(doc.tags[i], doc._id);
> >    }
> > }
> >
> > So now when I post {"keys": ["foo", "bar"]} to the view I get all the
> > documents tagged "foo", "bar", and also duplicates for any document that
> is
> > tagged with both.
> >
> > Is the best option to deduplicate the doc._id on the client and resubmit
> to
> > all docs, or can this be handled in a reduce function?
> >
> > Thank you for any help!
> >
> > Ross
> >
> > -----
> > @rossbates
> > rossbates.com
> >
>
> Assuming the set of tags you want to query isn't known until query
> time then you need to go with doing the client side intersection. A
> method for making this process a bit faster is to create a view that
> lists the tag count using a standard map/reduce of
> doc.tags.forEach(function(tag) {emit(tag, 1);}); and a reduce of
> "return sum(values)". Then query this view with the multi-key fetch to
> get the list of docids for each tag, then query in order of ascending
> counts.
>
> Paul Davis
>

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