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Date: Fri, 20 Nov 2009 12:15:59 +0000
Message-ID: <214c385b0911200415p18f6fa92yf69026ecfb7bec89@mail.gmail.com>
Subject: Re: Newbie :Filtering using complex key and array
From: Matt Goodall <matt.goodall@gmail.com>
To: user@couchdb.apache.org
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2009/11/20 Sebastien PASTOR <sebastien.pastor@gmx.com>:
> Sorry for the previous blank mail ... here is the content :
>
> Hi there,
>
> Pretty new to couchDB. I ve read a lot about couchdb and finally dive
> into it with a small project :)
> I am trying to do a simple thing and i am not sure at all if i am going
> the right way :
>
> my docs look like this :
>
> {
> =C2=A0"name":"Pizza Torino",
> =C2=A0 "delivery_areas":[75019,75018,75012,75013,75010],
> =C2=A0 =C2=A0 "type":"italian"
> =C2=A0 =C2=A0 }
>
> =C2=A0 =C2=A0 I managed to get =C2=A0all shops by type and get a reduce f=
unction to
> =C2=A0 =C2=A0 do the sum ( not much i know but still quite an accomplishm=
ent for
> =C2=A0 =C2=A0 me :) )
> =C2=A0 =C2=A0 I then tried to get my result filtered by delivery_areas. a=
s in
> =C2=A0 =C2=A0 getting only shop
> =C2=A0 =C2=A0 that do delivery in postal code 75019. I just could not =C2=
=A0have
> =C2=A0 =C2=A0 anything that
> =C2=A0 =C2=A0 worked using startkey and endkey ... is it the way to go or=
 is
> =C2=A0 =C2=A0 storing
> =C2=A0 =C2=A0 delivery_areas within an array not right ?
>
> =C2=A0 =C2=A0 my last map function looks like this :
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 "getShops" : {
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0"map" : "fu=
nction(doc){
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 emit([doc.deliver=
y_areas,doc.type],doc.name)
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 }
> =C2=A0 =C2=A0 }
>
> =C2=A0Thanks for pointing me to the right direction

Storing a list of delivery areas is good. The "trick" is to emit
multiple rows per document, e.g.

    function(doc) {
      for each (area in doc.delivery_areas) {
        emit([area, doc.type], doc.name);
      }
    }

You can then query with startkey=3D[75018, null] and endkey=3D[75018, {}]
to get all restaurants in the 75018 area.

The null and {} might look a bit weird at first but it's all to do
with how CouchDB orders rows in a view. See
http://wiki.apache.org/couchdb/View_collation#Collation_Specification
for details.

Hope this helps.

- Matt