goldmedal commented on code in PR #14440:
URL: https://github.com/apache/datafusion/pull/14440#discussion_r1957108526
##########
datafusion/expr-common/src/signature.rs:
##########
@@ -466,6 +551,133 @@ fn get_data_types(native_type: &NativeType) ->
Vec<DataType> {
}
}
+#[derive(Debug, Clone, Eq, PartialOrd)]
+pub enum Coercion {
Review Comment:
It would be great if add some doc for it and its variants.
##########
datafusion/expr-common/src/signature.rs:
##########
@@ -466,6 +551,133 @@ fn get_data_types(native_type: &NativeType) ->
Vec<DataType> {
}
}
+#[derive(Debug, Clone, Eq, PartialOrd)]
+pub enum Coercion {
+ Exact {
+ desired_type: TypeSignatureClass,
+ },
+ Implicit {
+ desired_type: TypeSignatureClass,
+ implicit_coercion: ImplicitCoercion,
+ },
+}
+
+impl Coercion {
+ pub fn new_exact(desired_type: TypeSignatureClass) -> Self {
+ Self::Exact { desired_type }
+ }
+
+ /// Create a new coercion with implicit coercion rules.
+ ///
+ /// `allowed_source_types` defines the possible types that can be coerced
to `desired_type`.
+ /// `default_casted_type` is the default type to be used for coercion if
we cast from other types via `allowed_source_types`.
+ pub fn new_implicit(
+ desired_type: TypeSignatureClass,
+ allowed_source_types: Vec<TypeSignatureClass>,
+ default_casted_type: NativeType,
+ ) -> Self {
+ Self::Implicit {
+ desired_type,
+ implicit_coercion: ImplicitCoercion {
+ allowed_source_types,
+ default_casted_type,
+ },
+ }
+ }
+
+ pub fn allowed_source_types(&self) -> &[TypeSignatureClass] {
+ match self {
+ Coercion::Exact { .. } => &[],
+ Coercion::Implicit {
+ implicit_coercion, ..
+ } => implicit_coercion.allowed_source_types.as_slice(),
+ }
+ }
+
+ pub fn default_casted_type(&self) -> Option<&NativeType> {
+ match self {
+ Coercion::Exact { .. } => None,
+ Coercion::Implicit {
+ implicit_coercion, ..
+ } => Some(&implicit_coercion.default_casted_type),
+ }
+ }
+
+ pub fn desired_type(&self) -> &TypeSignatureClass {
+ match self {
+ Coercion::Exact { desired_type } => desired_type,
+ Coercion::Implicit { desired_type, .. } => desired_type,
+ }
+ }
+
+ pub fn implicit_coercion(&self) -> Option<&ImplicitCoercion> {
+ match self {
+ Coercion::Exact { .. } => None,
+ Coercion::Implicit {
+ implicit_coercion, ..
+ } => Some(implicit_coercion),
+ }
+ }
+}
+
+impl Display for Coercion {
+ fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+ write!(f, "Coercion({}", self.desired_type())?;
+ if let Some(implicit_coercion) = self.implicit_coercion() {
+ write!(f, ", implicit_coercion={implicit_coercion}",)
+ } else {
+ write!(f, ")")
+ }
+ }
+}
+
+impl PartialEq for Coercion {
+ fn eq(&self, other: &Self) -> bool {
+ self.desired_type() == other.desired_type()
+ && self.implicit_coercion() == other.implicit_coercion()
+ }
+}
+
+impl Hash for Coercion {
+ fn hash<H: std::hash::Hasher>(&self, state: &mut H) {
+ self.desired_type().hash(state);
+ self.implicit_coercion().hash(state);
+ }
+}
+
+#[derive(Debug, Clone, Eq, PartialOrd)]
+pub struct ImplicitCoercion {
Review Comment:
We could also add some doc for it. Maybe adding some examples here is good.
I was confused about what it be used for before I did some tests.
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