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From Doğacan Güney (JIRA) <j...@apache.org>
Subject [jira] Commented: (HBASE-887) Fix a hotspot in scanners
Date Mon, 22 Sep 2008 23:21:46 GMT

    [ https://issues.apache.org/jira/browse/HBASE-887?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12633558#action_12633558

Doğacan Güney commented on HBASE-887:

I obviously am not comfortable with this code as any of you, but I have a few questions:

1) This patch adds a new method to HRegionInterface, shouldn't versionID be bumped?
2) I don't understand this part (frankly, this code is in hbase before this patch, but still:)

        HbaseMapWritable<byte [], Cell> values
          = new HbaseMapWritable<byte [], Cell>();
        HStoreKey key = new HStoreKey();
        TreeMap<byte [], Cell> results =
          new TreeMap<byte [], Cell>(Bytes.BYTES_COMPARATOR);
        while (s.next(key, results)) {

Why pass results to s.next and then put everything into values? Instance values is already
a SortedMap, we can directly pass values into s.next?

3) In ClientScanner#next, I think, if this.closed == true then method should not try to read
any more rows and just serve what is left in its cache, no? (Because in close(), ClientScanner
set closed to true and then makes callable a null)

> Fix a hotspot in scanners
> -------------------------
>                 Key: HBASE-887
>                 URL: https://issues.apache.org/jira/browse/HBASE-887
>             Project: Hadoop HBase
>          Issue Type: Improvement
>          Components: client, regionserver
>            Reporter: Jean-Daniel Cryans
>            Assignee: Jean-Daniel Cryans
>             Fix For: 0.19.0
>         Attachments: 877-chart.jpg, hbase-887-v1.patch
> When scanning, we do a lot of RPCs and this has a huge performance hit. I propose that
we add a way to fetch more rows during next() and put them in cache. This should be configurable.

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