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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9769) Improve performance of a Scanner with explicit column list when rows are small/medium size
Date Tue, 22 Oct 2013 06:14:54 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9769?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13801529#comment-13801529
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Lars Hofhansl commented on HBASE-9769:
--------------------------------------

We should test end-to-end, not a microbenchmark of StoreScanner.

Note that you cannot exercise the seeking code in checkVersion without returning data to the
client, in which case network IO will dominate. If you filter KVs out with a filter before
that checkVersion is never called, if the filter returns INCLUDE it'll call checkVersion and
incur a seek. Only with a coprocessor would it be possible to exercise checkVersion and avoid
the network IO.

Also note that in your filter case you'd still get the SEEK_NEXT_ROW/SEEK_NEXT_COL in ScanWildcardColumnTracker.checkVersion
for each column that you included.

When you get a chance, could you check out the last patch on HBASE-9778? Maybe you could run
it through your micro StoreScanner test, I'd be curious how it compares.

Generally, if that the column tracker code is not efficient we should fix that rather than
circumventing it completely with a filter.


> Improve performance of a Scanner with explicit column list when rows are small/medium
size
> ------------------------------------------------------------------------------------------
>
>                 Key: HBASE-9769
>                 URL: https://issues.apache.org/jira/browse/HBASE-9769
>             Project: HBase
>          Issue Type: Improvement
>          Components: Scanners
>    Affects Versions: 0.98.0, 0.94.12, 0.96.0
>            Reporter: Vladimir Rodionov
>            Assignee: Vladimir Rodionov
>         Attachments: 9769-0.94-sample1.txt, 9769-0.94-sample2.txt, 9769-0.94-sample.txt,
9769-94.txt, 9769-94-v2.txt, 9769-trunk-v1.txt, 9769-trunk-v2.txt, 9769-trunk-v3.txt, 9769-trunk-v4.txt
>
>




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