timsaucer commented on code in PR #24670:
URL: https://github.com/apache/datafusion/pull/24670#discussion_r3896905406
##########
datafusion/proto-models/src/generated/prost.rs:
##########
@@ -1178,6 +1178,8 @@ pub struct CastNode {
>,
#[prost(bool, optional, tag = "4")]
pub nullable: ::core::option::Option<bool>,
+ #[prost(message, optional, tag = "5")]
+ pub target_field: ::core::option::Option<super::datafusion_common::Field>,
Review Comment:
This and other places in this file are adding `pub` fields also making this
a breaking change.
##########
datafusion/expr/src/expr.rs:
##########
@@ -984,26 +983,76 @@ pub enum GetFieldAccess {
},
}
+/// Target of a cast expression.
+///
+/// A type-only target inherits metadata from the source expression. An
explicit
+/// field supplies its own metadata, including an empty map that clears source
+/// metadata.
+#[derive(Clone, PartialEq, Eq, PartialOrd, Hash, Debug)]
+pub enum CastTarget {
+ /// Cast to a data type while inheriting source metadata.
+ DataType(DataType),
+ /// Cast to an explicit field, including its metadata policy.
+ Field(FieldRef),
+}
+
+impl CastTarget {
+ /// Create a target that inherits source metadata.
+ pub fn type_only(data_type: DataType) -> Self {
+ Self::DataType(data_type)
+ }
+
+ /// Create an explicit field target.
+ pub fn explicit(field: FieldRef) -> Self {
+ Self::Field(field)
+ }
+
+ /// Return the target data type.
+ pub fn data_type(&self) -> &DataType {
+ match self {
+ Self::DataType(data_type) => data_type,
+ Self::Field(field) => field.data_type(),
+ }
+ }
+
+ /// Return the explicit target field, or `None` for a type-only target.
+ pub fn explicit_field(&self) -> Option<&FieldRef> {
+ match self {
+ Self::DataType(_) => None,
+ Self::Field(field) => Some(field),
+ }
+ }
+
+ /// Return explicit target metadata, or `None` when metadata is inherited.
+ pub fn metadata(&self) -> Option<&std::collections::HashMap<String,
String>> {
+ self.explicit_field().map(|field| field.metadata())
+ }
+}
+
/// Cast expression
#[derive(Clone, PartialEq, Eq, PartialOrd, Hash, Debug)]
pub struct Cast {
/// The expression being cast
pub expr: Box<Expr>,
- /// The `DataType` the expression will yield
- pub field: FieldRef,
+ /// The target type and metadata policy.
+ pub field: CastTarget,
Review Comment:
This is a breaking change of a public type, so if we go down this route this
PR will not be eligible for a backport to 55.
https://datafusion.apache.org/contributor-guide/release_management.html#backport-criteria
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