I think that JM brings up a good point. Keep in mind that RLL in HBase is not the same when you think of Row Level Locking in transactional systems. Depending on the use case... you can keep things in separate tables and not worry about the issues w CF's.
So when you think about your design... separate tables may be a valid design. IMHO I think more thought is needed before using CFs. The Essential column family sounds like its more beneficial for edge cases and not so much for the primary use case. Again, IMHO if you're using it for your primary use case, then I think you should rethink your schema design. To Ted's point, by keeping like data within CFs, it makes it easier when processing data within a M/R framework since your scanner will work against the CFs in the table. Yet, I have to ask why you would filter on one CF when pulling data from a second? Why not duplicate the data and store in both? Again, this is highly dependent on the use case. Just saying... On Apr 8, 2013, at 12:23 PM, Ted Yu <[email protected]> wrote: > Currently atomicity support in HBase is for single table, single region. > > If user chooses separate tables, it might be harder to implement the > business logic. > > On Mon, Apr 8, 2013 at 10:19 AM, Jean-Marc Spaggiari < > [email protected]> wrote: > >> Something I'm not getting, why not using separate tables instead of >> CFs for a single table? Simply name your table tablename_cfname then >> you get ride of the CF# limitation? >> >> Or is there big pros to have CFs? >> >> JM >> >> 2013/4/8 Anoop John <[email protected]>: >>> 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 <[email protected]> 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 <[email protected]> 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 <[email protected]> >>>>> To: [email protected] >>>>> 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 <[email protected]> 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 < >> [email protected] >>>>>> 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 < >>>> [email protected] >>>>>>>>> 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 >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>
