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From Anoop John <anoop.hb...@gmail.com>
Subject Re: Essential column family performance
Date Mon, 08 Apr 2013 17:10:02 GMT
Agree here. The effectiveness depends on what % of data satisfies the
condition, how it is distributed across HFile blocks. We will get
performance gain when the we will be able to skip some HFile blocks (from
non essential CFs). Can test with different HFile block size (lower value)?

-Anoop-


On Mon, Apr 8, 2013 at 8:19 PM, Ted Yu <yuzhihong@gmail.com> wrote:

> I made the following change in TestJoinedScanners.java:
>
> -      int flag_percent = 1;
> +      int flag_percent = 40;
>
> The test took longer but still favors joined scanner.
> I got some new results:
>
> 2013-04-08 07:46:06,959 INFO  [main] regionserver.TestJoinedScanners(157):
> Slow scanner finished in 7.424388 seconds, got 2050 rows
> ...
> 2013-04-08 07:46:12,010 INFO  [main] regionserver.TestJoinedScanners(157):
> Joined scanner finished in 5.05063 seconds, got 2050 rows
>
> 2013-04-08 07:46:18,358 INFO  [main] regionserver.TestJoinedScanners(157):
> Slow scanner finished in 6.348517 seconds, got 2050 rows
> ...
> 2013-04-08 07:46:22,946 INFO  [main] regionserver.TestJoinedScanners(157):
> Joined scanner finished in 4.587545 seconds, got 2050 rows
>
> Looks like effectiveness of joined scanner is affected by distribution of
> data.
>
> Cheers
>
> On Sun, Apr 7, 2013 at 8:52 PM, lars hofhansl <larsh@apache.org> wrote:
>
> > Looking at the joined scanner test code, it sets it up such that 1% of
> the
> > rows match, which would somewhat be in line with James' results.
> >
> > In my own testing a while ago I found a 100% improvement with 0% match.
> >
> >
> > -- Lars
> >
> >
> >
> > ________________________________
> >  From: Ted Yu <yuzhihong@gmail.com>
> > To: user@hbase.apache.org
> > Sent: Sunday, April 7, 2013 4:13 PM
> > Subject: Re: Essential column family performance
> >
> > I have attached 5416-TestJoinedScanners-0.94.txt to HBASE-5416 for your
> > reference.
> >
> > On my MacBook, I got the following results from the test:
> >
> > 2013-04-07 16:08:17,474 INFO  [main]
> regionserver.TestJoinedScanners(157):
> > Slow scanner finished in 7.973822 seconds, got 100 rows
> > ...
> > 2013-04-07 16:08:17,946 INFO  [main]
> regionserver.TestJoinedScanners(157):
> > Joined scanner finished in 0.47235 seconds, got 100 rows
> >
> > Cheers
> >
> > On Sun, Apr 7, 2013 at 4:03 PM, Ted Yu <yuzhihong@gmail.com> wrote:
> >
> > > Looking at
> > >
> >
> https://issues.apache.org/jira/secure/attachment/12564340/5416-0.94-v3.txt
> ,
> > I found that it didn't contain TestJoinedScanners which shows
> > > difference in scanner performance:
> > >
> > >    LOG.info((slow ? "Slow" : "Joined") + " scanner finished in " +
> > > Double.toString(timeSec)
> > >
> > >       + " seconds, got " + Long.toString(rows_count/2) + " rows");
> > >
> > > The test uses SingleColumnValueFilter:
> > >
> > >     SingleColumnValueFilter filter = new SingleColumnValueFilter(
> > >
> > >         cf_essential, col_name, CompareFilter.CompareOp.EQUAL,
> flag_yes);
> > > It is possible that the custom filter you were using would exhibit
> > > different access pattern compared to SingleColumnValueFilter. e.g. does
> > > your filter utilize hint ?
> > > It would be easier for me and other people to reproduce the issue you
> > > experienced if you put your scenario in some test similar to
> > > TestJoinedScanners.
> > >
> > > Will take a closer look at the code Monday.
> > >
> > > Cheers
> > >
> > > On Sun, Apr 7, 2013 at 11:37 AM, James Taylor <jtaylor@salesforce.com
> > >wrote:
> > >
> > >> Yes, on 0.94.6. We have our own custom filter derived from FilterBase,
> > so
> > >> filterIfMissing isn't the issue - the results of the scan are correct.
> > >>
> > >> I can see that if the essential column family has more data compared
> to
> > >> the non essential column family that the results would eventually even
> > out.
> > >> I was hoping to always be able to enable the essential column family
> > >> feature. Is there an inherent reason why performance would degrade
> like
> > >> this? Does it boil down to a single sequential scan versus many seeks?
> > >>
> > >> Thanks,
> > >>
> > >> James
> > >>
> > >>
> > >> On 04/07/2013 07:44 AM, Ted Yu wrote:
> > >>
> > >>> James:
> > >>> Your test was based on 0.94.6.1, right ?
> > >>>
> > >>> What Filter were you using ?
> > >>>
> > >>> If you used SingleColumnValueFilter, have you seen my comment here
?
> > >>> https://issues.apache.org/**jira/browse/HBASE-5416?**
> > >>> focusedCommentId=13541229&**page=com.atlassian.jira.**
> > >>> plugin.system.issuetabpanels:**comment-tabpanel#comment-**13541229<
> >
> https://issues.apache.org/jira/browse/HBASE-5416?focusedCommentId=13541229&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13541229
> > >
> > >>>
> > >>> BTW the use case Max Lapan tried to address has non essential column
> > >>> family
> > >>> carrying considerably more data compared to essential column family.
> > >>>
> > >>> Cheers
> > >>>
> > >>>
> > >>>
> > >>> On Sat, Apr 6, 2013 at 11:05 PM, James Taylor <
> jtaylor@salesforce.com
> > >>> >wrote:
> > >>>
> > >>>  Hello,
> > >>>> We're doing some performance testing of the essential column family
> > >>>> feature, and we're seeing some performance degradation when
> comparing
> > >>>> with
> > >>>> and without the feature enabled:
> > >>>>
> > >>>>                            Performance of scan relative
> > >>>> % of rows selected        to not enabling the feature
> > >>>> ---------------------    ------------------------------****--
> > >>>>
> > >>>> 100%                            1.0x
> > >>>>   80%                            2.0x
> > >>>>   60%                            2.3x
> > >>>>   40%                            2.2x
> > >>>>   20%                            1.5x
> > >>>>   10%                            1.0x
> > >>>>    5%                            0.67x
> > >>>>    0%                            0.30%
> > >>>>
> > >>>> In our scenario, we have two column families. The key value from
the
> > >>>> essential column family is used in the filter, while the key value
> > from
> > >>>> the
> > >>>> other, non essential column family is returned by the scan. Each
row
> > >>>> contains values for both key values, with the values being
> relatively
> > >>>> narrow (less than 50 bytes). In this scenario, the only time we're
> > >>>> seeing a
> > >>>> performance gain is when less than 10% of the rows are selected.
> > >>>>
> > >>>> Is this a reasonable test? Has anyone else measured this?
> > >>>>
> > >>>> Thanks,
> > >>>>
> > >>>> James
> > >>>>
> > >>>>
> > >>>>
> > >>>>
> > >>>>
> > >>>>
> > >>>>
> > >>
> > >
> >
>

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