[GitHub] [arrow] jorisvandenbossche commented on a change in pull request #7264: ARROW-8926: [C++] Improve arrow/compute/*.h comments, correct typos and outdated language

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

jorisvandenbossche commented on a change in pull request #7264:
URL: https://github.com/apache/arrow/pull/7264#discussion_r430269461



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File path: cpp/src/arrow/compute/kernel.h
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@@ -386,47 +435,75 @@ struct SimdLevel {
   enum type { NONE, SSE4_2, AVX, AVX2, AVX512, NEON };
 };
 
+/// \brief The strategy to use for propagating or otherwise populating the
+/// validity bitmap of a kernel output.
 struct NullHandling {
   enum type {
     /// Compute the output validity bitmap by intersecting the validity bitmaps
-    /// of the arguments. Kernel does not do anything with the bitmap
+    /// of the arguments. Kernel generally need not touch the bitmap
+    /// thereafter, but a kernel's exec function is permitted to alter the
+    /// bitmap after the null intersection is computed if it needs to.

Review comment:
       From this explanation, I find it not fully clear what "intersecting" means. 
   (is it where one of the arguments is null, or all or the argument is null, that the output validity indicates null?)




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