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From "Jonathan Hsieh (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8372) Provide mutability to CompoundConfiguration
Date Tue, 23 Apr 2013 17:07:17 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13639247#comment-13639247

Jonathan Hsieh commented on HBASE-8372:

If we are not arguing about correctness I'd like to commit this and file a follow on for perf

I'm not sure I buy your argument. It sounds like we potentially break semantics and use more
mem; both seem undesirable. If we do what you suggest we then end up copying the data everywhere
instead of sharing (ex: htabledescription[1][2][3] provides an sharable shallow copy of the
map map, in every region).  If we did what you suggest, we'd now have copy of each value into
a new mutableConf (an extra hash table entry per prop per region as opposed to a single pointer
to a singlethe htd table), and we lose the ability to propagate changes to the added map without
hunting down every instance present.  (if we change the table map, we'd need to hunt all instances
down to propagate htd changes to each regions conf.) 

[1] https://github.com/apache/hbase/blob/trunk/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java#L437
[2] https://github.com/apache/hbase/blob/trunk/hbase-client/src/main/java/org/apache/hadoop/hbase/HTableDescriptor.java#L1413
[3] https://github.com/apache/hbase/blob/trunk/hbase-client/src/main/java/org/apache/hadoop/hbase/HTableDescriptor.java#L488
> Provide mutability to CompoundConfiguration
> -------------------------------------------
>                 Key: HBASE-8372
>                 URL: https://issues.apache.org/jira/browse/HBASE-8372
>             Project: HBase
>          Issue Type: New Feature
>            Reporter: Ted Yu
>            Assignee: Jonathan Hsieh
>         Attachments: hbase-8372.patch, hbase-8372.v2.patch, hbase-8372.v3.patch, hbase-8372.v4.patch,
> In discussion of HBASE-8347, it was proposed that CompoundConfiguration should support
> This can be done by consolidating ImmutableConfigMap's on first modification to CompoundConfiguration.

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