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Date: Mon, 28 Jun 2010 12:52:50 -0400 (EDT)
From: "Damien Katz (JIRA)" <jira@apache.org>
To: dev@couchdb.apache.org
Subject: [jira] Commented: (COUCHDB-812) implement randomization in views
 resultset
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    [ https://issues.apache.org/jira/browse/COUCHDB-812?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12883212#action_12883212 ] 

Damien Katz commented on COUCHDB-812:
-------------------------------------

I think this is a fairly useful feature. Many moons ago I needs something similar in Lotus Notes, to randomly display a document from the database. It was difficult to get working.

It should be possible to do a random view get by randomly navigating btree nodes until you reach a leaf node. Though there will be some bias when the tree is unbalanced.

> implement randomization in views resultset
> ------------------------------------------
>
>                 Key: COUCHDB-812
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-812
>             Project: CouchDB
>          Issue Type: Wish
>          Components: Database Core
>    Affects Versions: 0.11
>         Environment: CouchDB
>            Reporter: Mickael Bailly
>            Priority: Minor
>
> This is a proposal for a new feature in CouchDB : allow a randomization of rows in a view response. We can for example add a randomize query parameter...
> This request would probably not return the same results for the same request.
> As an example :
> GET /db/_design/doc/_view/example :
> {
>   ..
>   rows: [
>     {key: 1 ...},
>     {key: 2 ...},
>     {key: 3 ...}
>   ]
> }
> GET /db/_design/doc/_view/example?randomize=true :
> {
>   ..
>   rows: [
>     {key: 2 ...},
>     {key: 3 ...},
>     {key: 1 ...}
>   ]
> }
> GET /db/_design/doc/_view/example?randomize=true :
> {
>   ..
>   rows: [
>     {key: 1 ...},
>     {key: 3 ...},
>     {key: 2 ...}
>   ]
> }
> This is a feature hard to implement client-side (but by reading all doc ids and use client-side random function). It's implemented by the RDBMS from ages, probably for the very same reasons : if we should read all the rows client-side to random-select some of them, performances are awful.

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