wiedld commented on code in PR #17249:
URL: https://github.com/apache/datafusion/pull/17249#discussion_r2286500937
##########
datafusion/expr/src/expr.rs:
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@@ -469,7 +469,50 @@ impl FieldMetadata {
}
/// Merges two optional `FieldMetadata` instances, overwriting any existing
- /// keys in `m` with keys from `n` if present
+ /// keys in `m` with keys from `n` if present.
+ ///
+ /// This function is commonly used in alias operations, particularly for
literals
+ /// with metadata. When creating an alias expression, the metadata from
the original
+ /// expression (such as a literal) is combined with any metadata specified
on the alias.
Review Comment:
This structure is intended for use with the aliasing of literals.
Since it has the same concept of field metadata `merge`, I felt it was
useful to add these docs in the same PR.
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