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https://issues.apache.org/jira/browse/PHOENIX-1146?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14086380#comment-14086380
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Andrew Purtell commented on PHOENIX-1146:
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bq. I do think that'd be an improvement, as it seems that the client cannot
always recover correctly based on the conversation in HBASE-11667.
Yes, if the coprocessor provides a synthetic key to the client instead of a
real row key at the current scan location then the client won't recover at this
time. Still discussing what, if anything, can be done there. Also, we could
consider an enhancement JIRA that implements a convention for coprocessors to
hint desired next action to a client scanner.
> Detect stale client region cache on server and retry scans in split regions
> ---------------------------------------------------------------------------
>
> Key: PHOENIX-1146
> URL: https://issues.apache.org/jira/browse/PHOENIX-1146
> Project: Phoenix
> Issue Type: Bug
> Affects Versions: 5.0.0, 3.1, 4.1
> Reporter: James Taylor
> Assignee: James Taylor
>
> HBase cannot recover correctly from an aggregate scan run on the coprocessor
> side (see HBASE-116670). This can lead to incorrect query results the first
> time a query is run after a split occurs (due to the region boundary cache
> being stale). Phoenix can work around this by:
> - detecting on server before the scan starts that the region cache used by
> the client is out-of-date. This can be done up-front because the start/stop
> row of the scan should never span across a region boundary. In this case, a
> DoNotRetryIOException is thrown with some embedded information to cause a
> StaleRegionBoundaryCacheException to be thrown on the client.
> - catching this exception on the client (in ParallelIterators), refreshing
> the region boundary cache, and re-running the necessary scans based on the
> new region boundaries.
> - detecting if this happens more than N times to prevent any kind of
> excessive looping due to splits occurring over and over again.
> Phoenix has additional requirements above and beyond standard HBase clients,
> so even if HBase could recover from this situation, Phoenix would likely need
> this workaround to ensure that a scan does not span across region boundaries.
> This is required when the client is doing a merge sort on the results of the
> parallel scans, mainly in ORDER BY (including topN) and local indexing, and
> potentially GROUP BY if we move toward sorting the distinct groups on the
> server side.
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