[jira] [Commented] (PHOENIX-2249) SYSTEM.STATS not update after region merge occurs.

["James Taylor (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PHOENIX-2249?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15038619#comment-15038619 ] 

James Taylor commented on PHOENIX-2249:
---------------------------------------

Thanks for the patch, [~ankit.singhal]. Looking at this closer, I'm confused because we already delete the stats for the regions being compacted when the InternalScanner returned from createCompactionScanner is closed (see calls to StatisticsWriter.deleteStats()). 

To be honest, I'm not sure what the HBase life cycle is when a merge occurs (i.e. when admin.mergeRegions() is called) - does it come through this same preCompact coprocessor hook? Is the merge operation distinct/orthogonal to a compaction? I expected there to be a merge coprocessor hook in which we'd just concatenate the stats information together (as two regions are now becoming one, but the content hasn't changed).

One high level comment - when we update stats, we collect up all the stats information in our StatisticsWriter and commit them in bulk so that they're updated atomically. 

> SYSTEM.STATS not update after region merge occurs.
> --------------------------------------------------
>
>                 Key: PHOENIX-2249
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-2249
>             Project: Phoenix
>          Issue Type: Bug
>         Environment: Ubuntu server 14.04
> Hadoop 2.6.0
> HBase 1.0.0
> Phoenix 4.4.0-HBase-1.0.0
>            Reporter: Kuan-Po Tseng
>            Assignee: Ankit Singhal
>             Fix For: 4.7.0
>
>         Attachments: PHOENIX-2249.patch
>
>
> When region merge occurs, SYSTEM.STATS does not update, it will leave stale information behind. And then if region splits on the merged region, this may cause 
> "org.apache.phoenix.schema.StaleRegionBoundaryCacheException: ERROR 1108 (XCL08): Cache of region boundaries are out of date" 
> after creating parallel scans since the stale information in SYSTEM.STATS will let guide post list not sorted in ascending order and this will cause scans over regions.



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