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https://issues.apache.org/jira/browse/HBASE-8372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13639247#comment-13639247
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Jonathan Hsieh commented on HBASE-8372:
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If we are not arguing about correctness I'd like to commit this and file a
follow on for perf concerns.
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, hbase-8372.v5.patch
>
>
> In discussion of HBASE-8347, it was proposed that CompoundConfiguration
> should support mutability.
> This can be done by consolidating ImmutableConfigMap's on first modification
> to CompoundConfiguration.
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