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https://issues.apache.org/jira/browse/HBASE-4823?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13156204#comment-13156204
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Phabricator commented on HBASE-4823:
------------------------------------
Kannan has accepted the revision "HBASE-4823 [jira] long running scans lose
benefit of bloomfilters and timerange hints".
Super!
+1 for commit.
REVISION DETAIL
https://reviews.facebook.net/D519
> long running scans lose benefit of bloomfilters and timerange hints
> -------------------------------------------------------------------
>
> Key: HBASE-4823
> URL: https://issues.apache.org/jira/browse/HBASE-4823
> Project: HBase
> Issue Type: Bug
> Reporter: Kannan Muthukkaruppan
> Assignee: Amitanand Aiyer
> Attachments: HBASE-4823.D519.1.patch, TestScannerResets-89fb.txt
>
>
> When you have a long running scan due to say an MR job, you can lose the
> benefit of timerange hints & bloom filters midway if your scanner gets reset.
> [Note: The scanners can get reset say due to a flush or compaction].
> In one of our workloads, we periodically want to do rollups on recent 15
> minutes of data in a column family... but the timerange hint benefit is lost
> midway when this resetScannerStack (shown below) happens. And end result-- we
> end up reading all the old HFiles rather than just the recent HFiles.
> {code}
> private void resetScannerStack(KeyValue lastTopKey) throws IOException {
> if (heap != null) {
> throw new RuntimeException("StoreScanner.reseek run on an existing
> heap!");
> }
> /* When we have the scan object, should we not pass it to getScanners()
> * to get a limited set of scanners? We did so in the constructor and we
> * could have done it now by storing the scan object from the constructor
> */
> List<KeyValueScanner> scanners = getScanners();
> {code}
> The comment in the code seems to be aware of this issue and even has the
> suggested fix!
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