jonahgao commented on code in PR #11542:
URL: https://github.com/apache/datafusion/pull/11542#discussion_r1685888821
##########
datafusion/expr/src/expr_schema.rs:
##########
@@ -112,7 +112,22 @@ impl ExprSchemable for Expr {
Expr::OuterReferenceColumn(ty, _) => Ok(ty.clone()),
Expr::ScalarVariable(ty, _) => Ok(ty.clone()),
Expr::Literal(l) => Ok(l.data_type()),
- Expr::Case(case) => case.when_then_expr[0].1.get_type(schema),
+ // Expr::Case(case) => case.when_then_expr[0].1.get_type(schema),
+ Expr::Case(case) => {
+ let then_type = case.when_then_expr[0].1.get_type(schema)?;
+ if !then_type.is_null() {
+ return Ok(then_type);
+ }
+
+ let else_type = case
+ .else_expr
+ .as_ref()
+ .map_or(Ok(DataType::Null), |e| e.get_type(schema))?;
+ if !else_type.is_null() {
+ return Ok(else_type);
+ }
+ Ok(DataType::Int64)
Review Comment:
This is because `type_coercion` will convert their types to `Utf8`.
```sh
| logical_plan after type_coercion | Projection:
arrow_typeof(CASE CAST(example.data AS Int64) WHEN Int64(1) THEN CAST(NULL AS
Utf8) WHEN Int64(2) THEN Utf8("FOO") ELSE CAST(NULL AS Utf8) END)
|
| | TableScan:
example
```
You can check this
[test](https://github.com/jonahgao/datafusion/blob/d9ff0cafd01614fe850ef4c12ba67761613336e8/datafusion/expr/src/expr_schema.rs#L677).
It does not perform type coercion.
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