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Benedict commented on CASSANDRA-9985:
-------------------------------------
bq. Can I bring up the icache boogyman?
You can. Since I'm it's main champion, it's a powerful weapon against me.
However in this case a little analysis shows that Guava doesn't even use its
own {{AbstractIterator}} (either of them!) very much at all. In fact nowhere
that we do, from what I can tell. I believe CASSANDRA-9471 uses
{{Iterables.mergeSorted}} which does - but we can perform a more efficient
merge since it's only 2-way, and otherwise should prefer our own Mergeiterator,
which has a more efficient heap implementation. So I will update it to avoid
using this function.
Which is a relief, since I am not in favour of overriding external packages if
we can avoid it, as it plays havoc with anyone wanting to use signed jars.
The only other place we use Guava {{AbstractIterator}} is in OHC. Since this is
the "HotKey" iterator, it is used infrequently and probably not to be troubled
over.
Of course, we do run the risk of in future introducing the occasional usage,
but those risks are small given how narrowly it is deployed in Guava. We have a
lot of minor issues around duplication, and we should probably file a ticket to
specifically track and fix it en masse. Especially regarding duplicate
functionality between Guava and java.util.function, but no harm setting up some
analysis for everything. It would be great if we had some automated analysis to
tell us of duplicate code candidates, in general. I'm certain such tools exist.
I'll take a look at purloining any Guava tests.
> Introduce our own AbstractIterator
> ----------------------------------
>
> Key: CASSANDRA-9985
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9985
> Project: Cassandra
> Issue Type: Sub-task
> Components: Core
> Reporter: Benedict
> Assignee: Benedict
> Priority: Trivial
> Fix For: 3.0.0 rc1
>
>
> The Guava AbstractIterator not only has unnecessary method call depth, it is
> difficult to debug without attaching source. Since it's absolutely trivial to
> write our own, and it's used widely within the codebase, I think we should do
> so.
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