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https://issues.apache.org/jira/browse/COUCHDB-812?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12883209#action_12883209
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Sebastian Cohnen commented on COUCHDB-812:
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It strongly depends on your particular use-case.
But if you really need to fetch large sets of purely random stuff, this is
always going to be a huge performance penalty, since you cannot utilize indexes
and stuff. If you want to avoid network overhead, you can use external
processes [1] to do that for you. You could query your external process via
couchdb, let the process build the set and send it back to you in one chunk.
[1] http://wiki.apache.org/couchdb/ExternalProcesses
> 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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