jonahgao commented on code in PR #15120:
URL: https://github.com/apache/datafusion/pull/15120#discussion_r1987404498
##########
datafusion/expr/src/expr.rs:
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@@ -392,11 +392,34 @@ impl Unnest {
}
/// Alias expression
-#[derive(Clone, PartialEq, Eq, PartialOrd, Hash, Debug)]
+#[derive(Clone, PartialEq, Eq, Debug)]
pub struct Alias {
pub expr: Box<Expr>,
pub relation: Option<TableReference>,
pub name: String,
+ pub metadata: Option<std::collections::HashMap<String, String>>,
Review Comment:
Aliases may be lost during expression rewriting. eg .
https://github.com/apache/datafusion/blob/a176aacc92a5b0272690bb48e7084ff5603ef7ad/datafusion/optimizer/src/analyzer/type_coercion.rs#L1018
According to the description of the PR, I think only columns/fields have
metadata, not all expressions.
`Field` already has customizable
[metadata](https://github.com/apache/arrow-rs/blob/f5138fcb10040e2428f2dd540177f5f224d0281e/arrow-schema/src/field.rs#L53);
is it possible to use it to meet the requirements🤔?
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