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From Jean-Daniel Cryans <jdcry...@apache.org>
Subject Re: writing and reading from a region at once
Date Thu, 25 Apr 2013 21:34:32 GMT


On Thu, Apr 25, 2013 at 1:09 PM, Aaron Zimmerman <
azimmerman@sproutsocial.com> wrote:

> Hi,
>   If a region is being written to, and a scanner takes a lease out on the
> region, what will happen to the writes?  Is there a concept of "Transaction
> Isolation Levels"?

There's MVCC, so reads can happen while someone else is writing. What you
should expect from HBase is "read committed".

>   I don't see errors in Puts while the tables are being scanned?  But it
> seems that I'm losing writes somewhere, is it possible the writes could
> fail silently?

 Is it temporary while you're scanning or there's really data missing at
the end of the day? The former might happen on some older HBase versions
while the latter should never happen unless you lower the durability level
yourself and have machine failures.


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