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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-7716) Row Groups / Row Family / Entity Groups in HBase
Date Wed, 30 Jan 2013 22:23:15 GMT

    [ https://issues.apache.org/jira/browse/HBASE-7716?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13566993#comment-13566993
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Enis Soztutar commented on HBASE-7716:
--------------------------------------

Thanks for feedback. 
bq. How do you propose carrying entity information on the Row?
As I imagine, this can be a part of the KV structure. We can either keep just an int, corresponding
to the length of the row group, and use prepend row key group to the actual row key. Or we
can keep that as a separate field in KV. 
bq. You imply that this functionality should be necessary for management of .META.. Can you
elaborate? Is there a related ticket?
Collected my thoughts at HBASE-7721.
bq. Is there a way for the user to change their mind about their entity groups? Say a group
grows too large; can I manually split it?
You have to rewrite the data because, key group will be a part of KV. This would be the main
limitation, but let's say you want to do smt like this as in megastore Entity Groups, ie.
in a single row, then you have the same problem of what if the row grows too big. 
bq. Row keys are fully optional, and backwards compatible.
It should have read row key <b>groups</b> are fully optional, and backwards compatible.
Meaning that if you are not using them, nothing changes for you. 
bq. FWIW, I think this feature can be emulated today using SplitPolicy configuration and application-level
rowkey prefix management. Perhaps a demonstration application is in order?
Yes this can be somehow emulated by custom row key prefix + custom region split policy + custom
coprocessors + custom filters. Not a thing an average user can do, plus you have to do this
per table. That is why I am in favor of the native approach of adding a row group to the data
model.
The best example, I think, is local transactions in META: HBASE-7721. 
bq. Row groups are not predefined, and are dynamic.
I think I have to reword this. I was thinking row groups as a part of KV, not dynamic in the
sense that you can change the row group of a row on the fly. They are dynamic in the sense
that, you don't have to define them in table creation time (like column families). 
In your example, you would use "com.example.www" as the row group while you are adding the
records. 


                
> Row Groups / Row Family / Entity Groups in HBase
> ------------------------------------------------
>
>                 Key: HBASE-7716
>                 URL: https://issues.apache.org/jira/browse/HBASE-7716
>             Project: HBase
>          Issue Type: New Feature
>          Components: Client, regionserver
>            Reporter: Enis Soztutar
>            Assignee: Enis Soztutar
>             Fix For: 0.98.0
>
>         Attachments: Entity Groups in HBase.txt
>
>
> This issue is to discuss the possible addition to the HBase data model for "Row Groups".
> As we are nearing 1.0, discussing this for 0.98 seems the right time, especially given
that we have custom region split policies, local transactions, and API overhaul around data
types -> bytes. 
> Row Groups are semantic groupings of rows in the Hbase data model. All rows within a
given row group share the same row group key. 
> Row groups are similar to column families in HBase or locality groups in BigTable, but
transposed to rows instead of columns. All the rows within a row group physically belong together,
and served by a single region. This means that region boundaries cannot split the row group.

> Row groups are not predefined, and are dynamic. There can be one row group per row. 
> Row keys are fully optional, and backwards compatible. 

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