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From "Lars Hofhansl (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-5229) Support atomic region operations
Date Sun, 22 Jan 2012 21:52:40 GMT

     [ https://issues.apache.org/jira/browse/HBASE-5229?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Lars Hofhansl updated HBASE-5229:
---------------------------------

    Attachment: 5229-seekto-v2.txt

Here's a patch that works. Regions are correctly addressed using the row key.
The region scanner will correctly skip all stores for families before the seekTo KV.
The first matching store will use the seekTo KV, the others will seek to the beginning of
the row (since their family sorts after the seekTo key).

The model possible here would be that a "transactional" table ends up being a row in HBase
(i.e. the row-key is the tablename), and a prefix of the columns defines "rows" inside that
table, the rest of the columns defines the actual "columns" of that row.

With this patch that is possible (set seekTo in Scan.java to seek inside a row, and enable
batching).

This patch provides no way to set a stop point inside a row. The client would need to set
batching to reasonable amount (to avoid too many roundtrips and at the same not to return
too many unnecessary KVs).
Also with a stop point, we could prune all stores whose family is past the stop point (just
like this patch prunes all stores with families before the stop point).
Because RegionScannerImpl and StoreScaner are inherently the row based the refactoring would
be non-trivial and risky.

I will now explore what it would take to define a grouping prefix in HTableDefinition.
                
> Support atomic region operations
> --------------------------------
>
>                 Key: HBASE-5229
>                 URL: https://issues.apache.org/jira/browse/HBASE-5229
>             Project: HBase
>          Issue Type: New Feature
>          Components: client, regionserver
>            Reporter: Lars Hofhansl
>            Assignee: Lars Hofhansl
>             Fix For: 0.94.0
>
>         Attachments: 5229-seekto-v2.txt, 5229-seekto.txt, 5229.txt
>
>
> As discussed (at length) on the dev mailing list with the HBASE-3584 and HBASE-5203 committed,
supporting atomic cross row transactions within a region becomes simple.
> I am aware of the hesitation about the usefulness of this feature, but we have to start
somewhere.
> Let's use this jira for discussion, I'll attach a patch (with tests) momentarily to make
this concrete.

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