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From Michael Segel <michael_se...@hotmail.com>
Subject RE: multiple scanners on same table will cause problem? Scan results change among different tries.
Date Thu, 22 Apr 2010 12:08:09 GMT

I'm sorry, but are you trying to say that you have multiple scanners trying to read from a
single region and the result sets do not match?

I guess it would be an easy test, enter a bunch of rows in to a region and have a unique integer
for each row. (1,2,3,...)
Then run a bunch of unfiltered scans in parallel, and generate a sum from the scan. If any
of the sums do not match, then you have a potential issue on concurency/row locking, and row
isolation level.  How does HBase handle row level locking and isolation levels?

-Mike

> Date: Thu, 22 Apr 2010 17:07:47 +0800
> Subject: multiple scanners on same table will cause problem? Scan results 	change among
different tries.
> From: steven.zhuang.1984@gmail.com
> To: hbase-user@hadoop.apache.org
> 
> hi, All,
>           Has anybody do scan on one table using multiple scanners at the
> same time and  found some inconsistent problem?
>           I am doing query on a table using dozens(20-120) of scanners in
> parallel(multiple threads), trying to take advantage of the multiple cores.
> But I found the scan results doesn't consist among several goes. I have
> checked my code, seems there is no bug in it. So I guess the problem may
> come from the HBase itself.
>           My HBase version is 0.20.3.
 		 	   		  
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