Github user mattf commented on the pull request:
https://github.com/apache/spark/pull/2093#issuecomment-53415478
> It's supposed that count() will cheaper than collect(), we call count()
instead of collect() to trigger the calculation in Scala/Java, It's better to
keep the same style in Python.
>
> But in PySpark, count() depends on collect(), which will dump the result
into disks and load them into Python. In future, this is maybe changed, count()
will returned a number from JVM.
>
> Right now, no strong reason to change collect() to count(), revert it?
thank you for the explaination, it wasn't clear from the code. my
preference is for isolated changes, so i'd suggest reverting and doing it
separately. however, others may not agree. so i'd say at least add a comment
about why count() is used -- someone might come along and change it back to
collect() without knowing they shouldn't.
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