[GitHub] [arrow] ianmcook edited a comment on pull request #10390: ARROW-12751: [C++] Implement minimum/maximum kernels

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ianmcook edited a comment on pull request #10390:
URL: https://github.com/apache/arrow/pull/10390#issuecomment-848823194


   > Can you explain what the point is of a variadic function when we don't have e.g. variadic addition?
   
   My understanding is that we are aiming for Arrow's compute API to reach parity with the collections of built-in functions available in popular SQL engines. These SQL engines include several variadic functions that combine/merge/aggregate values row-wise. Two such SQL functions are `greatest()` and `least()`. The two kernels implemented in this PR are equivalent to those two SQL functions. Another such SQL function is `concat()` and its variant `concat_ws()`, which we intend to implement in ARROW-12709.
   
   There are two ways we could implement this functionality without implementing variadic functions:
   1. Chain multiple calls to a binary function (as is required for addition of more than two values, as you mention)
   2. Combine the arrays row-wise into a ListArray, then operate on the ListArray with a unary function (ARROW-12739)
   
   If one of those alternative approaches is superior, then perhaps we do not need a variadic function. But my current understanding is that both of these alternative approaches are inferior for reasons of usability and efficiency respectively.


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