xitep opened a new pull request, #2103:
URL: https://github.com/apache/datafusion-sqlparser-rs/pull/2103
Right now `sqlparser-rs` injects the `AS` keyword in front of alias names
unconditionally. As reported by #1875 or #1784 this leads to problems on Oracle
databases. This patch preserves the original absence / presence of the
keyword (implicit/explicit aliases) in "table-factor" position when rendered
via `Display`.
1. Some more effort could be invested to apply the same behavior for
select-items (ie. projections in queries) and/or further nodes of the AST with
an alias for which `AS` is optional. To unify the implementation within the
parser and for clients, representing aliases could be exposed not as pure
`Ident`s but maybe as something as:
```rust
struct Alias {
explicit: bool,
name: Ident,
}
impl Deref for Alias {
type Target = Ident;
...
}
impl From<Alias> for Ident {
...
}
```
2. The parser _could_ be instructed / configured (either by `ParserOptions`
or through a `Dialect` setting) to always produce "explicit" alias tokens. This
would then always produce the "AS" keyword when render via `Display`. Ideally,
there would be a `VisitorMut::visit_(mut_)alias` and clients could just apply
their own setting easily. But this would be rather a nice-to-have.
3. I'd greatly appreciate a critical look since my know-how regarding
different DBs is quite limited. I hope I've not broken any of the existing
dialects and also hope this PR helps "preserving the syntax round trip".
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