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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-4119) Ability to add column families without disabling the table
Date Thu, 21 Jul 2011 06:47:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-4119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13068833#comment-13068833

Todd Lipcon commented on HBASE-4119:

Yes, I meant locality groups as Stack described above.

The advantages of allowing multiple column families to be in a single locality group are:
- people often want a way of grouping together sets of columns "logically" - you can certainly
use a prefix here, but the CF already seems like a natural prefix
- often times (especially if you're new to the data model) it's not clear what the correct
grouping of columns should be for your access patterns. Putting the different types of data
in different CFs, and then later being able to migrate CFs between locality groups allows
you to do the logical groupings up front, and then modify the physical groupings as the access
patterns become more clear later.
- BigTable has some properties that apply to column families and others that apply to locality
groups. For example, compression and block size are physical properties and thus apply to
the LG. TTL and version retention are logical properties and thus would apply to a column
family. I've often seen cases where two types of data are stored together in a CF for locality
reasons, but they really should have different TTL policies. Another example would be schema
information for use by a coprocessor that provides a secondary index.

> Ability to add column families without disabling the table
> ----------------------------------------------------------
>                 Key: HBASE-4119
>                 URL: https://issues.apache.org/jira/browse/HBASE-4119
>             Project: HBase
>          Issue Type: Improvement
>          Components: master, regionserver
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
> Support adding a new column family for a table without disabling the table.

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