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From "Anoop Sam John (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10885) Support visibility expressions on Deletes
Date Tue, 15 Apr 2014 06:02:36 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10885?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13969254#comment-13969254

Anoop Sam John commented on HBASE-10885:

bq. Do the delete handling in compaction because for the deleteColumn or deleteFamily cases
if we convert that delete request to a set of per-cell deletes, this could produce an explosion
of tombstones. 
bq.If we are not storing visibility expression terminals (LeafExpressionNodes) in sorted order
by ordinal we probably should consider it. (I don't think we are.) Because e.g. A|B == B|A.
It would be most efficient if we can simply do byte comparison of serialized visibility expressions
on the delete marker and any found while enumerating cells covered by it. 
Yes +1.

 So when we decide at the compaction time by direct byte compare of expressions in Delete
kv and other kvs, what abt the old HFile data written using 98.0 or 98.1 versions?  This will
be like not sorted.
Also it wont one simple bytes compare.   A&B will be stored as one Tag. In case of '|'
it will be stored as 2 tags.   So we need to consider all these tags and compare all.  Just
a note before starting the impl.

> 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
>             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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