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From: Paul Bonser <misterpib@gmail.com>
Date: Mon, 28 Jun 2010 17:08:24 -0500
Message-ID: <AANLkTimvP5xk65FjPGfLZaM_41-EoOXKlBuwcbQXZgc0@mail.gmail.com>
Subject: Re: Need to "subquery" in a view?
To: user@couchdb.apache.org
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Whoops, I must have been half asleep for that reply..., I got the key backw=
ard.

it should be "emit([doc._id, 0])" and startkey=3D[{userid, 0}], and
extrapolate from that for the rest. Swap the number and the user id.


On Mon, Jun 28, 2010 at 10:53 AM, Sean Coates <sean@seancoates.com> wrote:
>> The usual way that's done is talked about here in the "One to Many"
>> section: http://wiki.apache.org/couchdb/EntityRelationship
>>
>> Basically, you map function would be something like:
>>
>> =A0 =A0function(doc) {
>> =A0 =A0 =A0 =A0if (doc.type =3D=3D 'user') emit([0, doc._id], null);
>> =A0 =A0 =A0 =A0else if (doc.type =3D=3D 'asset') emit([1, doc.ownerid], =
null);
>> =A0 =A0}
>>
>> Then if you want to get the user and the assets they own, you would
>> query the view with startkey=3D[0, {userid}] and endkey=3D[1, {userid}],
>> and if you just want the list of assets owned by a certain user, you
>> use a startkey and endkey of [1, {userid}].
>
>
> I'm sorry if I'm being thick, but I don't quite understand how this would=
 work.
> Wouldn't a startkey=3D[0,{userid}]&endkey=3D[1,{userid}] match all users =
if {userid}=3D"1" ?
>
> I've adjusted my test data to make it more clear what's going on (see bel=
ow #1). u1 is not following u2 (now).
> If I query: start_key=3D[0,"u1"]&end_key=3D[1,"u1"]
> I get user records for all users (u1, u2, u3). I don't want u2 to be incl=
uded. (see below #2)
>
> Perhaps I'm not doing a very good job of explaining what I need to do.
> Does this make any more sense now?
>
> S
>
> (1)
> {"total_rows":9,"offset":0,"rows":[
> {"id":"_design/test","key":"_design/test","value":{"rev":"1-fecdec6331d23=
f13f7f40baef4ca6564"},"doc":{"_id":"_design/test","_rev":"1-fecdec6331d23f1=
3f7f40baef4ca6564","language":"javascript","views":{"join":{"map":" =A0 fun=
ction(doc) {\n =A0 =A0 =A0 if (doc.type =3D=3D 'user') emit([0, doc._id], n=
ull);\n =A0 =A0 =A0 else if (doc.type =3D=3D 'asset') emit([1, doc.ownerid]=
, null);\n =A0 }"}}}},
> {"id":"a4","key":"a4","value":{"rev":"2-e01f856361aef17a8b241114da1bcecb"=
},"doc":{"_id":"a4","_rev":"2-e01f856361aef17a8b241114da1bcecb","type":"ass=
et","ownerid":"u1"}},
> {"id":"a5","key":"a5","value":{"rev":"3-14db4d330452eb9f157e4a413227f4c8"=
},"doc":{"_id":"a5","_rev":"3-14db4d330452eb9f157e4a413227f4c8","type":"ass=
et","ownerid":"u1"}},
> {"id":"a6","key":"a6","value":{"rev":"3-e9f5d5c8ceaf8167c06d6751dcefb2df"=
},"doc":{"_id":"a6","_rev":"3-e9f5d5c8ceaf8167c06d6751dcefb2df","type":"ass=
et","ownerid":"u2"}},
> {"id":"a7","key":"a7","value":{"rev":"3-1706f210111b6fe15dec9d09eb9af47e"=
},"doc":{"_id":"a7","_rev":"3-1706f210111b6fe15dec9d09eb9af47e","type":"ass=
et","ownerid":"u3"}},
> {"id":"a8","key":"a8","value":{"rev":"3-1706f210111b6fe15dec9d09eb9af47e"=
},"doc":{"_id":"a8","_rev":"3-1706f210111b6fe15dec9d09eb9af47e","type":"ass=
et","ownerid":"u3"}},
> {"id":"u1","key":"u1","value":{"rev":"6-c3b4277626cd76b76b18b5acbff2edd8"=
},"doc":{"_id":"u1","_rev":"6-c3b4277626cd76b76b18b5acbff2edd8","type":"use=
r","following":["u3"]}},
> {"id":"u2","key":"u2","value":{"rev":"2-6b91b31ff9679d2a0a989f42a27ca496"=
},"doc":{"_id":"u2","_rev":"2-6b91b31ff9679d2a0a989f42a27ca496","type":"use=
r","following":["u1"]}},
> {"id":"u3","key":"u3","value":{"rev":"2-6b91b31ff9679d2a0a989f42a27ca496"=
},"doc":{"_id":"u3","_rev":"2-6b91b31ff9679d2a0a989f42a27ca496","type":"use=
r","following":["u1"]}}
> ]}
>
> (2)
> $ curl 'http://localhost:5984/test/_design/t/_view/join?start_key=3D%5B0%=
2C%22u1%22%5D&end_key=3D%5B1%2C%22u1%22%5B'
> {"total_rows":8,"offset":0,"rows":[
> {"id":"u1","key":[0,"u1"],"value":null},
> {"id":"u2","key":[0,"u2"],"value":null},
> {"id":"u3","key":[0,"u3"],"value":null},
> {"id":"a4","key":[1,"u1"],"value":null},
> {"id":"a5","key":[1,"u1"],"value":null},
> {"id":"a6","key":[1,"u2"],"value":null},
> {"id":"a7","key":[1,"u3"],"value":null},
> {"id":"a8","key":[1,"u3"],"value":null}
> ]}
>
>


--=20
Paul Bonser
http://probablyprogramming.com