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https://issues.apache.org/jira/browse/HBASE-19356?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16271652#comment-16271652
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Appy commented on HBASE-19356:
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Default implementations are great, but thinking about this problem, I am
beginning to think that they don't work well with delegator pattern.
I am assuming you use delegators to wrap objects given by HBase and augment
their functionality to match your needs? If so, default impl won't help them.
In fact, it might silently break them (that's why i said above that delegates
might not work well with default impl).
bq. It'd be helpful if HBase provided base implementations and delegates that
Phoenix could use instead.
My first impression was, delegates belong close to the patterns which require
it. Why should hbase provide delegates when they are not even needed inside
HBase.
But looking around more: RegionScanner is LP.COPROC and all implementations are
Private.
Which suggests that third-party can have their own RegionScanner impl but
should have nothing do to with internal impl. That's seems to be strong stance.
Unless users are doing something radically different, most will be just
augmenting parts of functionality to get by. Thinking about it, Phoneix is
radically big, but it's still doing that. Maybe we can have better design
around this.
I am +1 to provide delegators mainly because:
- It's trivial to maintain them, and very low cost
- Makes life of CP devs easier. If someone developed a CP around some feature
X, it's shouldn't break since entirely unrelated feature Y changed. For eg. X
can be extra metrics around existing functionality, and Y can be any new
feature adding anything to interface.
Let me ask what others think. If we go this way, would you be able to provide a
patch [~jamestaylor]? Please make sure to include a big class comment
mentioning it's place in overall CP design, justifying it's presence, example
of how it can be used by CP, etc.
What do you say [~apurtell], [~stack], [~mdrob]?
> Provide delegators and base implementation for Phoenix implemented interfaces
> -----------------------------------------------------------------------------
>
> Key: HBASE-19356
> URL: https://issues.apache.org/jira/browse/HBASE-19356
> Project: HBase
> Issue Type: Improvement
> Reporter: James Taylor
>
> Many of the changes Phoenix needs to make for various branches to support
> different versions of HBase are due to new methods being added to interfaces.
> Often times Phoenix can use a noop or simply needs to add the new method to
> it's delegate implementor. It'd be helpful if HBase provided base
> implementations and delegates that Phoenix could use instead. Here are some
> that come to mind:
> - RegionScanner
> - HTableInterface (Table interface now?)
> - RegionObserver
> There are likely others that [~rajeshbabu], [[email protected]], and
> [~elserj] would remember.
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