jayzhan211 commented on PR #12184:
URL: https://github.com/apache/datafusion/pull/12184#issuecomment-2311601582
> > The plan looks like aliasing to the same name after
`optimize_projections`
> > ```
> > Projection: test.a AS test.a
> > TableScan: test projection=[a]
> > ```
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> > I wonder could we even remove the alias here, since the name is the same
>
> Removing the Alias will cause a schema change. 🤔
That is why I think the root cause might be the incorrect schema we have.
`SELECT "test.a" FROM (SELECT a AS "test.a" FROM test)`
The expected schema should be something like.
```
DFSchema { inner: Schema { fields: [Field { name: "test.a", data_type:
Int32, nullable: true, dict_id: 0, dict_is_ordered: false, metadata: {} }],
metadata: {} }, field_qualifiers: [Some(Bare { table: "test" })],
functional_dependencies: FunctionalDependencies { deps: [] } }.
```
a is aliased to "test.a". The column should be `test."test.a"`
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