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From "Anoop Sam John (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PHOENIX-1278) Performance degradation for salted tables with guideposts
Date Tue, 23 Sep 2014 04:15:33 GMT

    [ https://issues.apache.org/jira/browse/PHOENIX-1278?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14144306#comment-14144306
] 

Anoop Sam John commented on PHOENIX-1278:
-----------------------------------------

bq.We should group the scans we're doing for the same bucket together and do a concat with
those results and then do a merge sort only with the concatenated batches.
Yes that will look great.
As of now we can go with temp off of guideposts for salted tables.

> Performance degradation for salted tables with guideposts
> ---------------------------------------------------------
>
>                 Key: PHOENIX-1278
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-1278
>             Project: Phoenix
>          Issue Type: Bug
>            Reporter: James Taylor
>
> When a table is salted, we're seeing a degradation in performance using our new guidepost-based
parallelization. With salted tables, we do a merge sort with the results from all the parallel
scans. I suspect the cause here is that we're doing a merge sort now between more chunks than
before (since we chunk everything up more now than we used to). We should group the scans
we're doing for the same bucket together and do a concat with those results and then do a
merge sort only with the concatenated batches.



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