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https://issues.apache.org/jira/browse/HBASE-9969?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13826388#comment-13826388
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Matt Corgan commented on HBASE-9969:
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Not sure how i didn't see it before, but here is the optimization that avoids
sending the scanner through the heap when the next KV is from the same scanner:
KeyValueHeap.pollRealKV() : line 350
{code}
// Compare the current scanner to the next scanner. We try to avoid
// putting the current one back into the heap if possible.
KeyValue nextKV = nextEarliestScanner.peek();
if (nextKV == null || comparator.compare(curKV, nextKV) < 0) {
// We already have the scanner with the earliest KV, so return it.
return kvScanner;
}
{code}
Does the LoserTreeKeyValueHeap do a check like that?
> Improve KeyValueHeap using loser tree
> -------------------------------------
>
> Key: HBASE-9969
> URL: https://issues.apache.org/jira/browse/HBASE-9969
> Project: HBase
> Issue Type: Improvement
> Components: Performance, regionserver
> Reporter: Chao Shi
> Assignee: Chao Shi
> Fix For: 0.98.0, 0.96.1
>
> Attachments: 9969-0.94.txt, KeyValueHeapBenchmark_v1.ods,
> hbase-9969-pq-v1.patch, hbase-9969-v2.patch, hbase-9969-v3.patch,
> hbase-9969.patch, hbase-9969.patch, kvheap-benchmark.png, kvheap-benchmark.txt
>
>
> LoserTree is the better data structure than binary heap. It saves half of the
> comparisons on each next(), though the time complexity is on O(logN).
> Currently A scan or get will go through two KeyValueHeaps, one is merging KVs
> read from multiple HFiles in a single store, the other is merging results
> from multiple stores. This patch should improve the both cases whenever CPU
> is the bottleneck (e.g. scan with filter over cached blocks, HBASE-9811).
> All of the optimization work is done in KeyValueHeap and does not change its
> public interfaces. The new code looks more cleaner and simpler to understand.
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