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https://issues.apache.org/jira/browse/HBASE-4823?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Phabricator updated HBASE-4823:
-------------------------------
Attachment: HBASE-4823.D519.1.patch
aaiyer requested code review of "HBASE-4823 [jira] long running scans lose
benefit of bloomfilters and timerange hints".
Reviewers: JIRA
Changes to the StoreScanner so that whenever we do a resetScannerStack
we use the same getScanner() method as done in the constructor to ignore
files that are not going to be touched by the scan.
Includes a test to ensure correctness.
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.
<span class="error">[Note: The scanners can get reset say due to a flush or
compaction]</span>.
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. <div
class="code panel" style="border-width: 1px;"><div class="codeContent
panelContent"> <pre class="code-java"><span class="code-keyword">private</span>
void resetScannerStack(KeyValue lastTopKey) <span
class="code-keyword">throws</span> IOException { <span
class="code-keyword">if</span> (heap != <span class="code-keyword">null</span>)
{ <span class="code-keyword">throw</span> <span
class="code-keyword">new</span> RuntimeException(<span
class="code-quote">"StoreScanner.reseek run on an existing heap!"</span>);
} /* 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();</pre> </div></div>
The comment in the code seems to be aware of this issue and even has the
suggested fix!
TEST PLAN
EMPTY
REVISION DETAIL
https://reviews.facebook.net/D519
AFFECTED FILES
src/test/java/org/apache/hadoop/hbase/regionserver/TestScannerResets.java
src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java
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> 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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