save-buffer commented on a change in pull request #11579:
URL: https://github.com/apache/arrow/pull/11579#discussion_r744073752
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File path: cpp/src/arrow/compute/exec/expression.h
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@@ -91,6 +91,9 @@ class ARROW_EXPORT Expression {
/// Return true if this expression could evaluate to true.
bool IsSatisfiable() const;
+ /// Return true if this expression has no clauses.
+ bool IsEmpty() const;
Review comment:
Thinking about it more, I'm not a big fan of this `literal(true)`
convention. Currently, null expressions are allowed (by calling the default
constructor). It's very bug-prone leaving code around that assumes expressions
are non-null while having no good way of checking this. Maybe instead of
introducing `IsEmpty` you can do `== Expression()`, but at that point I feel
`IsEmpty` is cleaner.
But anyway, If this is the convention, then the default constructor should
be deleted to eliminate the possibility of there ever being a null
`Expression`.
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