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https://issues.apache.org/jira/browse/BEAM-2980?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16487985#comment-16487985
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Kenneth Knowles commented on BEAM-2980:
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I can dig that perspective, too. The issue hitting users is probably that
"current" isn't as obvious to them.
Unfortunately I don't see a good transcript anywhere of the conversation
between the options of "XYZState is always a changing view of an underlying ref
cell" versus having a future-like API. It does see that the utility of
readLater() is tied to a particular implementation strategy wherein local
changes are buffered separately from whatever is read because of the hint.
TBH I just think futures are simpler. But I see that you'd need to refactor
bits of the API, for prefetching hint methods to cause futures to be delivered
elsewhere, versus imperative readLater() calls in the prefetch methods.
> BagState.isEmpty needs a tighter spec
> -------------------------------------
>
> Key: BEAM-2980
> URL: https://issues.apache.org/jira/browse/BEAM-2980
> Project: Beam
> Issue Type: Bug
> Components: beam-model
> Reporter: Kenneth Knowles
> Assignee: Daniel Mills
> Priority: Major
>
> Consider the following:
> {code}
> BagState<X> myBag = // empty
> ReadableState<Boolean> isMyBagEmpty = myBag.isEmpty();
> myBag.add(bizzle);
> bool empty = isMyBagEmpty.read();
> {code}
> Should {{empty}} be true or false? We need a consistent answer, across all
> kinds of state, when snapshots are required.
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