tustvold opened a new issue, #4680:
URL: https://github.com/apache/arrow-datafusion/issues/4680
**Is your feature request related to a problem or challenge? Please describe
what you are trying to do.**
Currently DataFusion has two ways to represent a schema, `Schema` and
`DFSchema`. The former is the representation used by arrow, and in most
components. `DFSchema` appears to "enhance" an arrow schema with the notion of
a qualifier.
I'm not entirely sure of the history of this split, but to the uninitiated
the split is confusing and frustrating. It also results in a non-trivial amount
of schema munging logic to convert to/from the relevant representations
**Describe the solution you'd like**
I would like to change `DfSchema` to be
```
struct DfSchema {
arrow_schema: SchemaRef,
field_metadata: Vec<DfFieldMetadata>
}
struct DfFieldMetadata {
qualifier: Option<String>,
}
```
We could then make `DfSchema` automatically deref to `SchemaRef`, or at the
very least implement `AsRef<SchemaRef>`, avoiding a lot of code that ends up
looking like
```
let schema: Schema = self.plan.schema().as_ref().into();
Arc::new(schema)
```
Components wishing to combine the information can easily zip the two
together, we could even assist this by adding
```
struct DfField<'a> {
field: &'a Field,
metadata: &'a DfFieldMetadata
}
```
**Describe alternatives you've considered**
We could not do this
**Additional context**
Add any other context or screenshots about the feature request here.
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