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https://issues.apache.org/jira/browse/HBASE-18165?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16037672#comment-16037672
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Josh Elser commented on HBASE-18165:
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bq. Filters or other transformations that run at compaction time are
essentially the Accumulo Iterators idea. We've had this proposed in other
contexts. I guess I have the same question now as then, why not implement
support for Accumulo-style Iterators?
The lay of abstract that Iterators provide is probably my favorite thing about
the system. The implementation isn't without its own warts, but it certainly
makes a nice layer of abstraction of operations over "streams" of data.
bq. Would that cover this predicate-based deletion also?
Could certainly do something which looks/feels like a Java8 streams filter. I
would say that limiting the kind of things people can do is probably better
than allowing arbitrary predicates. Like coprocessors, Accumulo iterators
suffer from people trying to use them as tools for something they weren't meant
to do.
For some context, Accumulo's "system" level deleting iterator (in this case,
handling delete tombstones in a row+column):
https://github.com/apache/accumulo/blob/f81a8ec7410e789d11941351d5899b8894c6a322/core/src/main/java/org/apache/accumulo/core/iterators/system/DeletingIterator.java
> Predicate based deletion during major compactions
> -------------------------------------------------
>
> Key: HBASE-18165
> URL: https://issues.apache.org/jira/browse/HBASE-18165
> Project: HBase
> Issue Type: Brainstorming
> Reporter: Lars Hofhansl
>
> In many cases it is expensive to place a delete per version, column, or
> family.
> HBase should have way to specify a predicate and remove all Cells matching
> the predicate during the next compactions (major and minor).
> Nothing more concrete. The tricky part would be to know when it is safe to
> remove the predicate, i.e. when we can be sure that all Cells matching the
> predicate actually have been removed.
> Could potentially use HBASE-12859 for that.
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