larry98 commented on code in PR #43256:
URL: https://github.com/apache/arrow/pull/43256#discussion_r1693708865
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cpp/src/arrow/compute/expression.cc:
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@@ -1242,8 +1271,74 @@ struct Inequality {
/*insert_implicit_casts=*/false, &exec_context);
}
+ /// Simplify an `is_in` value set against an inequality guarantee.
+ ///
+ /// Simplifying an `is_in` predicate involves filtering out any values from
+ /// the value set that cannot possibly be found given the guarantee. For
+ /// example, if we have the predicate 'x is_in [1, 2, 3, 4]' and the
guarantee
+ /// 'x > 2', then the simplified predicate 'x is_in [3, 4]' is equivalent.
+ /// This can be done efficiently if the value set is sorted and unique by
+ /// binary searching the inequality gound and slicing the value set
+ /// accordingly.
+ ///
+ /// \pre `guarantee` is non-nullable
+ /// \pre `value_set` is non-empty
+ /// \return a simplified value set, or a bool if the simplification results
in
+ /// a boolean literal predicate.
+ static Result<std::variant<std::shared_ptr<Array>, bool>>
SimplifyIsInValueSet(
Review Comment:
`true` can be returned if the guarantee is an equality e.g. `x is_in [1, 2,
3]` given the guarantee `x = 2` simplifies to `true`.
But I'm fine with skipping this simplification if you think that would be
better.
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