waynexia commented on issue #2994:
URL:
https://github.com/apache/arrow-datafusion/issues/2994#issuecomment-1203421200
>It seems a little strange that self.name and self.get_type have different
behavior.
`Expr::name()` is nothing more than a string concat, it won't find whether
this column exists in schema. In other words, it won't return an error due to
the wrong schema or column:
```rust
fn create_name(e: &Expr, input_schema: &DFSchema) -> Result<String> {
match e {
Expr::Alias(_, name) => Ok(name.clone()),
Expr::Column(c) => Ok(c.flat_name()),
Expr::Literal(value) => Ok(format!("{:?}", value)),
Expr::BinaryExpr { left, op, right } => {
let left = create_name(left, input_schema)?;
let right = create_name(right, input_schema)?;
Ok(format!("{} {} {}", left, op, right))
}
.. => {}
}
```
But `get_type` and `get_nullable` can't. The type and nullable info are
stored in schema.
BTW, It looks like the `input_schema` is not used in this function. Maybe we
can remove it.
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