[jira] [Updated] (HBASE-10805) Speed up KeyValueHeap.next() a bit

["Lars Hofhansl (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-10805?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Lars Hofhansl updated HBASE-10805:
----------------------------------

    Attachment: 10805-trunk.txt

Trunk patch to get a test run through, just to be sure.

> 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
>             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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