brian.goetz at oracle.com
Wed Apr 3 19:34:25 PDT 2013
At one point, we had an unordered() op. I think it may be time to bring
There are a growing number of ops that have optimized implementations
for unordered streams:
- distinct can be implemented with concurrent insertion into a CHS
instead of merging if we don't care about order. Not only is this less
work (merging is expensive), but it makes distinct lazy (elements can
flow through immediately once they've not been found in the CHS, instead
of waiting for all the elements to be seen.)
- sorted is non-stable in unordered streams.
- limit/subsequence are far lighter for unordered streams (and can
similarly be made lazy)
So a way of saying "I know you think this stream has ordering, but I
don't care about it" is a way of opting into these optimizations.
Implementation is trivial.
Adding .unordered() could also enable us to get rid of
.collectUnordered(), and allow more of the reduce-like ops to benefit
from the embrace of "disorder" without API explosion.
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