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HBase >> mail # user >> best read path explanation


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S Ahmed 2013-01-13, 15:24
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Anoop John 2013-01-13, 16:29
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lars hofhansl 2013-01-14, 02:33
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S Ahmed 2013-01-14, 18:37
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Asaf Mesika 2013-01-14, 18:47
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Re: best read path explanation
This in enforced in the serverside scanner framework (ScanQueryMatcher called by StoreScanner).
So while expired KeyValues are only physically only removed once a compaction runs, they are logically hidden by the scanner framework.
In fact the same scanner framework is used to decide whether KeyValues are visible to a user scan or during a compaction.
As for Ahmed's question, you can run the tests locally by just applying the patch to a svn checkout (I doubt it will still apply, though).
-- Lars

________________________________
 From: Asaf Mesika <[EMAIL PROTECTED]>
To: "[EMAIL PROTECTED]" <[EMAIL PROTECTED]>
Cc: lars hofhansl <[EMAIL PROTECTED]>
Sent: Monday, January 14, 2013 10:47 AM
Subject: Re: best read path explanation
 

I have a follow up question here: 
A column family can be defined to have a maximum number of versions per column qualifier value. Is this enforced only by the client side code (HTable) or also by the InternalScanner implementations?

On Monday, January 14, 2013, S Ahmed  wrote:

Thanks Lars!
>
>Sort of a side question after following your proposed patch:
>https://issues.apache.org/jira/secure/attachment/12511771/5268-v5.txt
>
>Locally on your computer (laptop?), can those tests run in isolation or you
>need a fairly complicated setup to run them? (all the various hbase
>dependancies like zookeeper etc).
>
>
>On Sun, Jan 13, 2013 at 9:33 PM, lars hofhansl <[EMAIL PROTECTED]> wrote:
>
>> Does this help:
>> http://hadoop-hbase.blogspot.com/2012/01/scanning-in-hbase.html ?
>>
>>
>>
>>
>> ________________________________
>>  From: S Ahmed <[EMAIL PROTECTED]>
>> To: [EMAIL PROTECTED]
>> Sent: Sunday, January 13, 2013 7:24 AM
>> Subject: best read path explanation
>>
>> What is the best hbase read path explanation?
>>
>> I understand that hbase stores data and doesn't allow for mutations, so I'm
>> confused as to how a read can get the latest data?
>>
>> I'm guessing there are merges done between the immutable file stores, and
>> in-memory stores?
>>
>