Implicit aliases #2103
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Implicit aliases #2103
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Right now `sqlparser-rs` inject the `AS` keyword in front of aliases unconditionally. As reported by apache#1875 or apache#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 `SelectItem`s (ie. projections in queries) and 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 then 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 easily apply their own preference. 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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Right now
sqlparser-rsinjects theASkeyword 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 viaDisplay.ASis optional. To unify the implementation within the parser and for clients, representing aliases could then be exposed not as pureIdents but maybe as something as:The parser could be instructed / configured (either by
ParserOptionsor through aDialectsetting) to always produce "explicit" alias tokens. This would then always produce the "AS" keyword when render viaDisplay. Ideally, there would be aVisitorMut::visit_(mut_)aliasand clients could just apply their own setting easily. But this would be rather a nice-to-have.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".