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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10885) Support visibility expressions on Deletes
Date Fri, 25 Apr 2014 00:01:20 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10885?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13980520#comment-13980520
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Andrew Purtell commented on HBASE-10885:
----------------------------------------

On sorting of terminals or not, a discussion that Ram, Anoop, and I included this topic and
it seems reasonable to change the serialization. I think we should start by splitting out
the custom visibility tag serialization in VisibilityController to a separate file. We could
put magic bytes in front and test for those, falling back to an expensive comparison of we
don't find the magic, otherwise use one optimized for sorted representation. While we are
at it we could use protobuf for the new serialization and so the magic preamble would be 'PBUF'
I suppose. 

> Support visibility expressions on Deletes
> -----------------------------------------
>
>                 Key: HBASE-10885
>                 URL: https://issues.apache.org/jira/browse/HBASE-10885
>             Project: HBase
>          Issue Type: Improvement
>    Affects Versions: 0.98.1
>            Reporter: Andrew Purtell
>            Assignee: ramkrishna.s.vasudevan
>            Priority: Critical
>             Fix For: 0.99.0, 0.98.2
>
>
> Accumulo can specify visibility expressions for delete markers. During compaction the
cells covered by the tombstone are determined in part by matching the visibility expression.
This is useful for the use case of data set coalescing, where entries from multiple data sets
carrying different labels are combined into one common large table. Later, a subset of entries
can be conveniently removed using visibility expressions.
> Currently doing the same in HBase would only be possible with a custom coprocessor. Otherwise,
a Delete will affect all cells covered by the tombstone regardless of any visibility expression
scoping. This is correct behavior in that no data spill is possible, but certainly could be
surprising, and is only meant to be transitional. We decided not to support visibility expressions
on Deletes to control the complexity of the initial implementation.



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