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Date: Sat, 22 Mar 2014 10:28:42 +0000 (UTC)
From: "Hudson (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] [Commented] (HBASE-10805) Speed up KeyValueHeap.next() a bit
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    [ https://issues.apache.org/jira/browse/HBASE-10805?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13943993#comment-13943993 ] 

Hudson commented on HBASE-10805:
--------------------------------

FAILURE: Integrated in HBase-TRUNK #5033 (See [https://builds.apache.org/job/HBase-TRUNK/5033/])
HBASE-10805 Speed up KeyValueHeap.next() a bit (larsh: rev 1580149)
* /hbase/trunk/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/KeyValueHeap.java


> Speed up KeyValueHeap.next() a bit
> ----------------------------------
>
>                 Key: HBASE-10805
>                 URL: https://issues.apache.org/jira/browse/HBASE-10805
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>             Fix For: 0.99.0, 0.94.19, 0.98.2, 0.96.3
>
>         Attachments: 10805-trunk.txt
>
>
> See discussion on HBASE-9969.
> This was brought up by [~mcorgan]. Even though I didn't believe him first.
> {code}
>       KeyValueScanner topScanner = this.heap.peek();
>       if (topScanner == null ||
>           this.comparator.compare(kvNext, topScanner.peek()) >= 0) {
>         this.heap.add(this.current);
>         this.current = pollRealKV();
>       }
> {code}
> We already have the invariant everywhere this.current always has a real KV polled. So adding current back to the heap followed by pollRealKV() is a no-op if this.current is the only scanner anyway.
> This can be changed to:
> {code}
>       ...
>       if (topScanner != null &&
>           this.comparator.compare(kvNext, topScanner.peek()) >= 0) {
>       ...
> {code}
> With 20m rows, 5 cols each, everything in the cache, fully compacted - i.e. one HFile per store, a scan that filters everything at the server through all 100m KVs takes 15.1s without the change and 13.3s with it, so a 12% improvement.


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