hbase-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7051) Read/Updates (increment,checkAndPut) should properly read MVCC
Date Sun, 28 Oct 2012 04:17:13 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7051?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13485565#comment-13485565
] 

Lars Hofhansl commented on HBASE-7051:
--------------------------------------

I'd probably go with #1 honestly (as I said above it's not as nuclear as I had thought). I
do not think #2 or #3 are worth the effort/risk.

We always wait for all other transactions - in this region - to finish (that is true even
for normal puts), this is a nice and simple design in HBase. Changing that to MVCC/row would
also break the multi row transaction stuff I added (but that is only exposed through a coprocessor
endpoint so breaking that would potentially be OK).

MVCC is already per region, I do not think we should add a finer granularity here.

                
> Read/Updates (increment,checkAndPut) should properly read MVCC
> --------------------------------------------------------------
>
>                 Key: HBASE-7051
>                 URL: https://issues.apache.org/jira/browse/HBASE-7051
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.96.0
>            Reporter: Gregory Chanan
>             Fix For: 0.94.3, 0.96.0
>
>
> See, for example:
> {code}
> // TODO: Use MVCC to make this set of increments atomic to reads
> {code}
> Here's an example of what I can happen (would probably be good to write up a test case
for each read/update):
> Concurrent update via increment and put.
> The put grabs the row lock first and updates the memstore, but releases the row lock
before the MVCC is advanced.  Then, the increment grabs the row lock and reads right away,
reading the old value and incrementing based on that.
> There are a few options here:
> 1) Waiting for the MVCC to advance for read/updates: the downside is that you have to
wait for updates on other rows.
> 2) Have an MVCC per-row (table configuration): this avoids the unnecessary contention
of 1)
> 3) Transform the read/updates to write-only with rollup on read..  E.g. an increment
 would just have the number of values to increment.

--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira

Mime
View raw message