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From: Apache Wiki <wikidiffs@apache.org>
To: Apache Wiki <wikidiffs@apache.org>
Date: Thu, 07 Jan 2010 09:51:31 -0000
Message-ID: <20100107095131.13434.44867@eos.apache.org>
Subject: 
 =?utf-8?q?=5BCouchdb_Wiki=5D_Update_of_=22Introduction=5Fto=5FCouchDB=5Fv?=
 =?utf-8?q?iews=22_by_BrianCandler?=

Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Couchdb Wiki" for c=
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The "Introduction_to_CouchDB_views" page has been changed by BrianCandler.
The comment on this change is: Note about equal keys and docids.
http://wiki.apache.org/couchdb/Introduction_to_CouchDB_views?action=3Ddiff&=
rev1=3D25&rev2=3D26

--------------------------------------------------

  =

  For queries which are not meant to actually condense the amount of inform=
ation you often can live without a reduce function. A common strategy is to=
 get the data you are interested to select by in into the ''key'' part and =
then use ''startkey'' and ''endkey'' on the result.
  =

+ =3D=3D Equal keys =3D=3D
+ =

+ CouchDB actually stores the [key,docid] pair as the key in the btree. Thi=
s means that:
+  * you always know which document the key and value came from (it's expos=
ed as the 'id' field in the view result)
+  * view rows with equal keys sort by increasing docid.
+ =

+ If you assign your docids in a time-based way then you can get documents =
with equal keys in a natural oldest-to-newest order. Couchdb has a feature =
to do this, which you can enable in local.ini:
+ =

+ {{{
+ [uuids]
+ algorithm =3D utc_random
+ }}}
+ =

  =3D=3D Lookup Views =3D=3D
  =

- The second parameter of the ''emit()'' function can be ''NULL''. CouchDB =
then only stores the key in the view. If you use the document's ID here, yo=
u can use the view as a compact lookup mechanism and fetch the document's d=
etails, if needed, in subsequent requests.
+ The second parameter of the ''emit()'' function can be ''null''. CouchDB =
then only stores the [key,docid] in the view. You can use the view as a com=
pact lookup mechanism and fetch the document's details, if needed, in subse=
quent requests or by adding parameter ''include_docs=3Dtrue''
  =

  =3D=3D Complex Keys =3D=3D
 =20