goldmedal commented on code in PR #1551:
URL:
https://github.com/apache/datafusion-sqlparser-rs/pull/1551#discussion_r1882455970
##########
src/parser/mod.rs:
##########
@@ -1427,6 +1426,112 @@ impl<'a> Parser<'a> {
}
}
+ /// Try to parse an [Expr::CompoundExpr] like `a.b.c` or `a.b[1].c`.
+ /// If all the fields are `Expr::Identifier`s, return an
[Expr::CompoundIdentifier] instead.
+ /// If only the root exists, return the root.
+ /// If self supports [Dialect::supports_partiql], it will fall back when
occurs [Token::LBracket] for JsonAccess parsing.
+ pub fn parse_compound_expr(
+ &mut self,
+ root: Expr,
+ mut chain: Vec<AccessField>,
+ ) -> Result<Expr, ParserError> {
+ let mut ending_wildcard: Option<TokenWithSpan> = None;
+ let mut ending_lbracket = false;
+ while self.consume_token(&Token::Period) {
+ let next_token = self.next_token();
+ match next_token.token {
+ Token::Word(w) => {
+ let expr = Expr::Identifier(w.to_ident(next_token.span));
+ chain.push(AccessField::Expr(expr));
+ if self.consume_token(&Token::LBracket) {
+ if self.dialect.supports_partiql() {
+ ending_lbracket = true;
+ break;
+ } else {
+ self.parse_multi_dim_subscript(&mut chain)?
+ }
+ }
+ }
+ Token::Mul => {
+ // Postgres explicitly allows funcnm(tablenm.*) and the
+ // function array_agg traverses this control flow
+ if dialect_of!(self is PostgreSqlDialect) {
+ ending_wildcard = Some(next_token);
+ break;
+ } else {
+ return self.expected("an identifier after '.'",
next_token);
+ }
+ }
+ Token::SingleQuotedString(s) => {
+ let expr = Expr::Identifier(Ident::with_quote('\'', s));
+ chain.push(AccessField::Expr(expr));
+ }
+ _ => {
+ return self.expected("an identifier or a '*' after '.'",
next_token);
+ }
+ }
+ }
+
+ // if dialect supports partiql, we need to go back one Token::LBracket
for the JsonAccess parsing
+ if self.dialect.supports_partiql() && ending_lbracket {
+ self.prev_token();
+ }
+
+ if let Some(wildcard_token) = ending_wildcard {
Review Comment:
@iffyio
I feel the idea of this loop is good but I found a problem 🤔 . If we try to
invoke `parse_subexpr` recursively, we will still get the nested
representation. Consider the following cases:
## The representation of abc[1].f1.f2
The last field is a `CompoundIdentifier`.
```
&root = Identifier(
Ident {
value: "abc",
quote_style: None,
span: Span(Location(0,0)..Location(0,0)),
},
)
&chain = [
Subscript(
Index {
index: Value(
Number(
"1",
false,
),
),
},
),
Dot(
CompoundIdentifier(
[
Ident {
value: "f1",
quote_style: None,
span: Span(Location(0,0)..Location(0,0)),
},
Ident {
value: "f2",
quote_style: None,
span: Span(Location(0,0)..Location(0,0)),
},
],
),
),
]
```
## The representation of abc[1].f1.f2[1]
The last field is a `CompoundFieldAccess` with another chain.
```
&root = Identifier(
Ident {
value: "abc",
quote_style: None,
span: Span(Location(0,0)..Location(0,0)),
},
)
&chain = [
Subscript(
Index {
index: Value(
Number(
"1",
false,
),
),
},
),
Dot(
CompoundFieldAccess {
root: Identifier(
Ident {
value: "f1",
quote_style: None,
span: Span(Location(0,0)..Location(0,0)),
},
),
access_chain: [
Dot(
CompoundFieldAccess {
root: Identifier(
Ident {
value: "f2",
quote_style: None,
span: Span(Location(0,0)..Location(0,0)),
},
),
access_chain: [
Subscript(
Index {
index: Value(
Number(
"1",
false,
),
),
},
),
],
},
),
],
},
),
]
```
It seems we should consider `CompoundIdentifier` and `CompoundFieldAccess`
as a kind of the nested struct.
Ideally, the access_cahin shouldn't contain another nested struct.
The `parse_subexpr` shouldn't produce the nested struct 🤔. It makes the
thing more complicated.
I don't prefer to do It in this PR. The side effects will be too large.
Maybe we can have a follow-up PR to refactor here.
WDYT?
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