alamb commented on code in PR #10117:
URL: https://github.com/apache/datafusion/pull/10117#discussion_r1592934687
##########
datafusion/expr/src/signature.rs:
##########
@@ -346,13 +346,61 @@ impl Signature {
}
}
-/// Monotonicity of the `ScalarFunctionExpr` with respect to its arguments.
-/// Each element of this vector corresponds to an argument and indicates
whether
-/// the function's behavior is monotonic, or non-monotonic/unknown for that
argument, namely:
-/// - `None` signifies unknown monotonicity or non-monotonicity.
-/// - `Some(true)` indicates that the function is monotonically increasing
w.r.t. the argument in question.
-/// - Some(false) indicates that the function is monotonically decreasing
w.r.t. the argument in question.
-pub type FuncMonotonicity = Vec<Option<bool>>;
+#[derive(Debug, Clone)]
+enum FuncMonotonicityPartial {
+ /// not monotonic or unknown monotonicity
+ None,
+ /// Increasing with respect to all of its arguments
+ Increasing,
+ /// Decreasing with respect to all of its arguments
+ Decreasing,
+ /// Each element of this vector corresponds to an argument and indicates
whether
+ /// the function's behavior is monotonic, or non-monotonic/unknown for
that argument, namely:
+ /// - `None` signifies unknown monotonicity or non-monotonicity.
+ /// - `Some(true)` indicates that the function is monotonically increasing
w.r.t. the argument in question.
+ /// - Some(false) indicates that the function is monotonically decreasing
w.r.t. the argument in question.
+ Mixed(Vec<Option<bool>>),
+}
+
+/// Monotonicity of a function with respect to its arguments.
+///
+/// A function is [monotonic] if it preserves the relative order of its inputs.
+///
+/// [monotonic]: https://en.wikipedia.org/wiki/Monotonic_function
+#[derive(Debug, Clone)]
+pub struct FuncMonotonicity(FuncMonotonicityPartial);
+
+impl FuncMonotonicity {
+ pub fn new_none() -> Self {
+ Self(FuncMonotonicityPartial::None)
+ }
+ pub fn new_increasing() -> Self {
+ Self(FuncMonotonicityPartial::Increasing)
+ }
+ pub fn new_decreasing() -> Self {
+ Self(FuncMonotonicityPartial::Decreasing)
+ }
+ pub fn new_mixed(inner: Vec<Option<bool>>) -> Self {
+ Self(FuncMonotonicityPartial::Mixed(inner))
+ }
+}
+
+impl From<&FuncMonotonicity> for Vec<Option<bool>> {
+ fn from(val: &FuncMonotonicity) -> Self {
+ match &val.0 {
+ FuncMonotonicityPartial::None => vec![None],
+ FuncMonotonicityPartial::Increasing => vec![Some(true)],
+ FuncMonotonicityPartial::Decreasing => vec![Some(false)],
+ FuncMonotonicityPartial::Mixed(inner) => inner.to_vec(),
+ }
+ }
+}
+
+impl PartialEq for FuncMonotonicity {
+ fn eq(&self, other: &Self) -> bool {
+ Into::<Vec<Option<bool>>>::into(self) ==
Into::<Vec<Option<bool>>>::into(other)
Review Comment:
Something like this perhaps:
```rust
match (self, other) {
(Self::None, None) => true,
(Self::Increasing, Self::Increasing) => true,
(Self::Decreasing, Self::Decreasing) => true,
(Self::Partial(self_inner), Self::Partial(other_inner)) => self_inner ==
other_inner,
_ => false
}
```
##########
datafusion/expr/src/signature.rs:
##########
@@ -346,13 +346,61 @@ impl Signature {
}
}
-/// Monotonicity of the `ScalarFunctionExpr` with respect to its arguments.
-/// Each element of this vector corresponds to an argument and indicates
whether
-/// the function's behavior is monotonic, or non-monotonic/unknown for that
argument, namely:
-/// - `None` signifies unknown monotonicity or non-monotonicity.
-/// - `Some(true)` indicates that the function is monotonically increasing
w.r.t. the argument in question.
-/// - Some(false) indicates that the function is monotonically decreasing
w.r.t. the argument in question.
-pub type FuncMonotonicity = Vec<Option<bool>>;
+#[derive(Debug, Clone)]
+enum FuncMonotonicityPartial {
+ /// not monotonic or unknown monotonicity
+ None,
+ /// Increasing with respect to all of its arguments
+ Increasing,
+ /// Decreasing with respect to all of its arguments
+ Decreasing,
+ /// Each element of this vector corresponds to an argument and indicates
whether
+ /// the function's behavior is monotonic, or non-monotonic/unknown for
that argument, namely:
+ /// - `None` signifies unknown monotonicity or non-monotonicity.
+ /// - `Some(true)` indicates that the function is monotonically increasing
w.r.t. the argument in question.
+ /// - Some(false) indicates that the function is monotonically decreasing
w.r.t. the argument in question.
+ Mixed(Vec<Option<bool>>),
+}
+
+/// Monotonicity of a function with respect to its arguments.
+///
+/// A function is [monotonic] if it preserves the relative order of its inputs.
+///
+/// [monotonic]: https://en.wikipedia.org/wiki/Monotonic_function
+#[derive(Debug, Clone)]
+pub struct FuncMonotonicity(FuncMonotonicityPartial);
+
+impl FuncMonotonicity {
+ pub fn new_none() -> Self {
+ Self(FuncMonotonicityPartial::None)
+ }
+ pub fn new_increasing() -> Self {
+ Self(FuncMonotonicityPartial::Increasing)
+ }
+ pub fn new_decreasing() -> Self {
+ Self(FuncMonotonicityPartial::Decreasing)
+ }
+ pub fn new_mixed(inner: Vec<Option<bool>>) -> Self {
+ Self(FuncMonotonicityPartial::Mixed(inner))
+ }
+}
+
+impl From<&FuncMonotonicity> for Vec<Option<bool>> {
+ fn from(val: &FuncMonotonicity) -> Self {
+ match &val.0 {
+ FuncMonotonicityPartial::None => vec![None],
+ FuncMonotonicityPartial::Increasing => vec![Some(true)],
+ FuncMonotonicityPartial::Decreasing => vec![Some(false)],
+ FuncMonotonicityPartial::Mixed(inner) => inner.to_vec(),
+ }
+ }
+}
Review Comment:
I agree with @ozankabak it is confusing to have a way to convert back to
`Vec<Option<bool>>` -- I think it would be easier to understand if all
comparisons are done directly on `FuncMonotonicity` rather than converting to
Vec<Option<Bool>>
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