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https://issues.apache.org/jira/browse/HBASE-14826?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15008553#comment-15008553
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ramkrishna.s.vasudevan commented on HBASE-14826:
------------------------------------------------
Using the benchmark class attached in HBASE-9969 and testing reseek with and
without the patch
With patch
========
next/reseek,numColsPerRow,prefixLength,impl,numScanners,opsPerSec(K),topScannerNull(K),next
comparisons(K),heap comparisons(K),GS comparisons(K)
reseek,16,0,KVHeap,1,2987,0,0,-0,0
reseek,16,0,KVHeap,2,2724,0,0,-0,0
reseek,16,0,KVHeap,4,3329,0,0,-0,0
reseek,16,0,KVHeap,8,4333,0,0,-0,0
reseek,16,0,KVHeap,16,3495,0,0,-0,0
reseek,16,0,KVHeap,32,3361,0,0,-0,0
Without patch
==========
next/reseek,numColsPerRow,prefixLength,impl,numScanners,opsPerSec(K),topScannerNull(K),next
comparisons(K),heap comparisons(K),GS comparisons(K)
reseek,16,0,KVHeap,1,2539,0,0,-0,0
reseek,16,0,KVHeap,2,2118,0,0,-0,0
reseek,16,0,KVHeap,4,2675,0,0,-0,0
reseek,16,0,KVHeap,8,3628,0,0,-0,0
reseek,16,0,KVHeap,16,2583,0,0,-0,0
reseek,16,0,KVHeap,32,2284,0,0,-0,0
Where the 6th col indicates the opsPerSec. We can see a gain of 7% to 10%
> Small improvement in KVHeap seek() API
> --------------------------------------
>
> Key: HBASE-14826
> URL: https://issues.apache.org/jira/browse/HBASE-14826
> Project: HBase
> Issue Type: Improvement
> Reporter: ramkrishna.s.vasudevan
> Assignee: ramkrishna.s.vasudevan
> Priority: Minor
> Attachments: HBASE-14826.patch
>
>
> Currently in seek/reseek() APIs we tend to do lot of priorityqueue related
> operations. We initially add the current scanner to the heap, then poll and
> again add the scanner back if the seekKey is greater than the topkey in that
> scanner. Since the KVs are always going to be in increasing order and in
> ideal scan flow every seek/reseek is followed by a next() call it should be
> ok if we start with checking the current scanner and then do a poll to get
> the next scanner. Just avoid the initial PQ.add(current) call. This could
> save some comparisons.
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