jonahgao commented on code in PR #11542:
URL: https://github.com/apache/datafusion/pull/11542#discussion_r1685744627
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datafusion/expr/src/expr_schema.rs:
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@@ -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:
Although I think returning `DataType::Int64` can make it work fine, because
after type coercion it always returns `then_type`. But it is still strange, the
type of `CASE data WHEN 1 THEN NULL WHEN 2 THEN 'FOO' ELSE NULL END` is
`DataType::Int64`.
How about returning the first non-NULL type among the `then` and `else`
expressions?
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