Weijun-H commented on code in PR #11542:
URL: https://github.com/apache/datafusion/pull/11542#discussion_r1685875278
##########
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:
Current implementation will return the first non-NULL type among the then
and else expressions.
``` shell
> select arrow_typeof(CASE data WHEN 1 THEN NULL WHEN 2 THEN 'FOO' ELSE NULL
END )from example;
+------------------------------------------------------------------------------------------------------+
| arrow_typeof(CASE example.data WHEN Int64(1) THEN NULL WHEN Int64(2) THEN
Utf8("FOO") ELSE NULL END) |
+------------------------------------------------------------------------------------------------------+
| Utf8
|
| Utf8
|
| Utf8
|
| Utf8
|
+------------------------------------------------------------------------------------------------------+
```
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