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https://issues.apache.org/jira/browse/COUCHDB-2182?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13917742#comment-13917742
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Gabe Malicki commented on COUCHDB-2182:
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This looks great. I'm glad to hear it's already in the works. I'm closing
this ticket
> Why doesn't couchdb support multiple keys requests to a reduce function using
> group_level ?
> -------------------------------------------------------------------------------------------
>
> Key: COUCHDB-2182
> URL: https://issues.apache.org/jira/browse/COUCHDB-2182
> Project: CouchDB
> Issue Type: Question
> Security Level: public(Regular issues)
> Components: Database Core, HTTP Interface
> Reporter: Gabe Malicki
>
> Why doesn't couchdb support multiple keys requests to a reduce function using
> group_level ? I need this functionality in order to reduce the amount of
> network IO and latency in my system. Perhaps it would be possible to
> implement this with a warning about the cost of such a query.
> Here is my example real-world use case:
> I have a database of widgets that are being voted on by web users and I have
> a reduce function that computes different types of ranking for each widget
> based on the widget's numerical properties in conjunction with user votes (1
> to 10). There are far too many widgets to sort in the client and couchdb
> does not allow the sorting of view query results by value. This means in
> order to be able to get the widgets sorted by their ranking I need to first
> write the reduce function output (score results for each widget) to a
> database so that I can later query on that data sorted by score.
> As new votes enter the system they are bulk_saved then a separate view reduce
> query is executed for each effected widget to calculate the new scores then
> those scores are bulk_saved into a db so that they can later be queried
> sorted by their various scores. Since couchdb doesn't allow querying
> multiple keys with my reduce function using group_level I'm having to make 20
> HTTP GET requests if 20 different widgets were voted on instead of a single
> HTTP GET and all of this extra network io means I have to fire off a bunch of
> threads to block on network IO which is expensive and this cost becomes
> greater the more votes I need to process per minute.
> Adding multiple keys query with group_level would reduce the amount of CPU,
> latency, and bandwidth that I'm having to burn in order to achieve reduce
> function sorting by value. Of course if someone could figure out how to let
> me sort reduce output by value then that would save me even more resources.
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