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Date: Tue, 7 Aug 2012 17:30:02 -0700 (PDT)
From: lars hofhansl <lhofhansl@yahoo.com>
Reply-To: lars hofhansl <lhofhansl@yahoo.com>
Subject: Re: CheckAndAppend Feature
To: "user@hbase.apache.org" <user@hbase.apache.org>,
  lars hofhansl <lhofhansl@yahoo.com>
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I filed HBASE-6522. It is a trivial change to make locks and leases available to coprocessors.
So checkAndSet type operations can then be implemented via coprocessor endpoints: lock row, check, fail or update, unlock row.

Since the patch is so simple I'll commit that soon (to 0.94.2 and 0.96)


-- Lars

________________________________
From: lars hofhansl <lhofhansl@yahoo.com>
To: "user@hbase.apache.org" <user@hbase.apache.org> 
Sent: Tuesday, August 7, 2012 8:55 AM
Subject: Re: CheckAndAppend Feature

There is no such functionality currently, and there is no good way to simulate that.

Currently that cannot even be done with a coprocessor endpoint, because region coprocessors have no way to create a region lock (just checked the code).
(That is something we have to change I think - I will create an issue once the Jira system is back from the walk in the park).

-- Lars


----- Original Message -----
From: Jerry Lam <chilinglam@gmail.com>
To: user <user@hbase.apache.org>
Cc: 
Sent: Tuesday, August 7, 2012 8:22 AM
Subject: CheckAndAppend Feature

Hi HBase community:

I checked the HTable API, it has checkAndPut and checkAndDelete but I'm
looking for checkAndAppend. Is there a way to simulate similarly?
For instance, I want to check the last 32 bytes of a value (let assume that
it has 128 bytes in total) in a column before appending atomically some
values into it.

Thanks!

Jerry