cyb70289 commented on code in PR #13222:
URL: https://github.com/apache/arrow/pull/13222#discussion_r880034314
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cpp/src/arrow/compute/exec/expression.cc:
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@@ -107,9 +107,10 @@ ValueDescr Expression::descr() const {
return CallNotNull(*this)->descr;
}
+const std::shared_ptr<DataType> kNoType;
Review Comment:
Nit: wrap it inside an anonymous namespace, or as static global?
Did a quick comparison of `local static` and `global`. Looks for normal case
(not the first time access which is complex due to thread safety), `local
static` has the penalty of additional load-compare-cond_jump. Guess it may
cause observable effect on microbenchmark.
https://godbolt.org/z/cxWPhccnx
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