gstvg commented on code in PR #18921:
URL: https://github.com/apache/datafusion/pull/18921#discussion_r3022045503
##########
datafusion/expr/src/expr_schema.rs:
##########
@@ -199,6 +203,13 @@ impl ExprSchemable for Expr {
// Grouping sets do not really have a type and do not appear
in projections
Ok(DataType::Null)
}
+ Expr::HigherOrderFunction(_func) => {
+ Ok(self.to_field(schema)?.1.data_type().clone())
+ }
+ Expr::Lambda(Lambda { params: _, body }) => body.get_type(schema),
Review Comment:
It's either this, `DataType::Null` or an error. I don't have a strong
opinion on this, actually. Right now, the only place I call it is literally
like this:
```rust
.map(|arg: Expr| {
let field = arg.to_field(schema)?.1;
match arg {
Expr::Lambda(_lambda) => Ok(ValueOrLambda::Lambda(field)),
_ => Ok(ValueOrLambda::Value(field)),
}
})
```
We can just change it to
```rust
.map(|arg: Expr| {
match arg {
Expr::Lambda(lambda) =>
Ok(ValueOrLambda::Lambda(lambda.body.to_field(schema)?.1)),
_ => Ok(ValueOrLambda::Value(arg.to_field(schema)?.1)),
}
})
```
During higher order function type coercion, lambda arguments are ignored and
only value arguments are checked and coerced so the return type for a lamba is
irrelevant.
Some other expressions return `DataType::Null` like logical `Placeholder`
without a specifed type, `Wildcard` and `GroupingSet` and physical `NoOp` and
`UnknownColumn`. If you think that's better I'm happy to change it
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