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https://issues.apache.org/jira/browse/HBASE-18029?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16006176#comment-16006176
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Duo Zhang commented on HBASE-18029:
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[~appy] I found it is really hard to keep compatibility here. The problem is
that, StoreFile.Reader is an instance of StoreFileReader, but StoreFileReader
is not an instance of StoreFile.Reader. The StoreFile is also marked as
IA.LimitedPrivate(without IS annotation...) so if we want to also keep
compatibility then we must still declare the return value of createReader as
StoreFile.Reader. So here comes the problem, we add new methods in coprocessor
which return a StoreFileReader instead of StoreFile.Reader. These methods will
be called in StoreFile.Reader. If a user implements the new method and returns
a StoreFileReader, how can we cast it to a StoreFile.Reader instance?
And in fact, most of our IA.LimitPrivate(CP) classes are declared as
IS.Evolving which means it is allowed to break the compatibility between minor
releases. But practically, it is not a good idea to break compatibility between
minor releases. It is a pain for the downstream projects. I think we need to
revisit the IS annotations.
And for the StoreFile related classes, I think a big problem is that, we expose
a class instead of an interface to CP, and the class is not only a data
strcuture. I suggest that we make interfaces for both StoreFile,
StoreFileReader and StoreFileWriter if we really need to expose them to CP. The
work should be done before 2.0 release.
What do you think? [~stack] [~apurtell] [~lhofhansl].
Thanks.
> Backport HBASE-15296 to branch-1
> --------------------------------
>
> Key: HBASE-18029
> URL: https://issues.apache.org/jira/browse/HBASE-18029
> Project: HBase
> Issue Type: Improvement
> Components: regionserver
> Reporter: Duo Zhang
>
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