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Date: Sun, 5 Oct 2014 12:00:49 -0700
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Subject: Re: View question
From: Stanley Iriele <siriele2x3@gmail.com>
To: user@couchdb.apache.org, Giovanni Parra <fiatjaf@gmail.com>
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chaining map reduce sounds really exciting....but for your current
solution...list functions would be the way to go

On Sun, Oct 5, 2014 at 10:03 AM, Giovanni P <fiatjaf@gmail.com> wrote:

> as I always have trouble imagining the results of a some reduce function
> with group_level and stuff alike, I made this app for quickly simulating
> these things: http://fiatjaf.github.io/couchdb-mr-simulator/
>
> here's the same simulation Aur=C3=A9lien did:
>
> http://fiatjaf.github.io/couchdb-mr-simulator/#{%22params%22:%22reduceFn:=
%20_count\nreduce:%20true\ngroup:%20true\ngroup_level:%202\nstartkey:%20[20=
13]\nendkey:%20[2014,%20{}]%22,%22emitted%22:%222012,%20\%22A\%22\n2012,%20=
\%22B\%22\n2012,%20\%22C\%22\n2013,%20\%22A\%22\n2013,%20\%22A\%22\n2013,%2=
0\%22A\%22\n2013,%20\%22C\%22\n2014,%20\%22A\%22\n2014,%20\%22A\%22\n2014,%=
20\%22B\%22%22}
> <
> http://fiatjaf.github.io/couchdb-mr-simulator/#%7B%22params%22:%22reduceF=
n:%20_count%5Cnreduce:%20true%5Cngroup:%20true%5Cngroup_level:%202%5Cnstart=
key:%20[2013]%5Cnendkey:%20[2014,%20%7B%7D]%22,%22emitted%22:%222012,%20%5C=
%22A%5C%22%5Cn2012,%20%5C%22B%5C%22%5Cn2012,%20%5C%22C%5C%22%5Cn2013,%20%5C=
%22A%5C%22%5Cn2013,%20%5C%22A%5C%22%5Cn2013,%20%5C%22A%5C%22%5Cn2013,%20%5C=
%22C%5C%22%5Cn2014,%20%5C%22A%5C%22%5Cn2014,%20%5C%22A%5C%22%5Cn2014,%20%5C=
%22B%5C%22%22%7D
> >
>
> On Sun, Oct 5, 2014 at 9:05 AM, Aur=C3=A9lien B=C3=A9nel <aurelien.benel@=
utt.fr>
> wrote:
>
> > > Thanks Aur=C3=A9lien for a better explanation of my problem :-)
> >
> > Good to hear :)
> >
> > For the additional computation step, you can:
> >
> > 1. switch to CloudAnt's BigCouch to get chained mapreduce
> >     http://examples.cloudant.com/sales/_design/sales/index.html
> >
> > 2. or wait for BigCouch integration into Apache CouchDB (in version 2.0=
)
> >     https://issues.apache.org/jira/browse/COUCHDB/fixforversion/1231557=
2
> >
> > 3.  or "cheat" and do it with a list.
> >
> >
> > Regards,
> >
> > Aur=C3=A9lien
> >
> >
> > >>>> I need to filter by date and group by group...
> > >>> You can use the second with group_level=3D1 and get all the groups =
at
> the
> > >> same time. And you can use _count
> > >>
> > >>
> > >> I'm afraid this is not so easy...
> > >> Using a filter by date will also *group* by date.
> > >>
> > >> Let's take a very simple example...
> > >>
> > >> Here are keys emitted by a map:
> > >> [2012, 'A']
> > >> [2012, 'B']
> > >> [2012, 'C']
> > >> [2013, 'A']
> > >> [2013, 'A']
> > >> [2013, 'A']
> > >> [2013, 'C']
> > >> [2014, 'A']
> > >> [2014, 'A']
> > >> [2014, 'B']
> > >>
> > >> If we query it with `_count` as the reduce function, `group=3Dtrue`,
> > >> `startkey=3D[2013]` and `endkey=3D[2014,{}]`, we'll get:
> > >> [2013, 'A'] -> 3
> > >> [2013, 'C'] -> 1
> > >> [2014, 'A']      -> 2
> > >> [2014, 'B'] -> 1
> > >>
> > >> Boaz will need additional computation to get:
> > >> 'A' -> 5
> > >> 'B' -> 1
> > >> 'C' -> 1
> > >>
> > >>
> > >> Regards,
> > >>
> > >> Aur=C3=A9lien
> >
> >
>

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