[GitHub] [accumulo] ctubbsii commented on issue #1764: Parallelize calls to InstanceOperations.getActiveCompactions() in listcompactions shell command

[GitBox <gi...@apache.org>]

ctubbsii commented on issue #1764:
URL: https://github.com/apache/accumulo/issues/1764#issuecomment-722810021


   > I am uncertain if the stream will have the same order as the current iterator class, I am not sure if tservers will stay grouped together in output and if the age order created inside flatMap will be preserved.
   
   It looks like the order of this one will depend on which tservers respond first, but within a tserver, it looks like they'll still be grouped and ordered correctly within a tserver. They could be grouped and sorted by tserver with an intermediate multimap or something, though.
   
   While I don't think the flatMap will mess with the ordering, it does look like it will prevent parallelization, without using the collector strategy I mentioned above. Otherwise, the first item will call go through `map`, `flatMap`, `map`, `filter`, and `iterator` on the first call to `next` in the iterator... and the second one will wait until `next` is called again. This is what the collector strategy I posted above avoids... it ensures all of them are iterated, during the `collect` phase, and then operates on the collection with the `collectingAndThen` special-purpose collector.


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