[GitHub] [arrow] jorgecarleitao commented on a change in pull request #7988: ARROW-9783: [Rust] [DataFusion] Remove aggregate expression data type

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jorgecarleitao commented on a change in pull request #7988:
URL: https://github.com/apache/arrow/pull/7988#discussion_r472221795



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File path: rust/datafusion/src/logicalplan.rs
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@@ -363,8 +335,6 @@ pub enum Expr {
         name: String,
         /// List of expressions to feed to the functions as arguments
         args: Vec<Expr>,
-        /// The `DataType` the expression will yield
-        return_type: DataType,

Review comment:
       I agree with this: we need two interfaces: one internal that supports variable types, so that we abstract out the hard-coded return types and make them functions of the expression, and a public one for users to declared fixed-type UDFs.




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