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Simplify parse_window_frame

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It used to consume the `RParen` closing the encompassing `OVER (`, even
when no window frame was parsed, which confused me a bit, even though
I wrote it initially.

After fixing that, I took the opportunity to reduce nesting and
duplication a bit.
This commit is contained in:
Nickolay Ponomarev 2019-07-07 05:53:53 +03:00
parent 9314371d3b
commit f31636d339
1 changed files with 24 additions and 29 deletions
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53
src/parser.rs
View file

@ -294,7 +294,13 @@ impl Parser {
} else {
vec![]
};
let window_frame = self.parse_window_frame()?;
let window_frame = if !self.consume_token(&Token::RParen) {
let window_frame = self.parse_window_frame()?;
self.expect_token(&Token::RParen)?;
Some(window_frame)
} else {
None
};
Some(WindowSpec {
partition_by,
@ -313,35 +319,24 @@ impl Parser {
}))
}
pub fn parse_window_frame(&mut self) -> Result<Option<WindowFrame>, ParserError> {
let window_frame = match self.peek_token() {
Some(Token::Word(w)) => {
let units = w.keyword.parse::<WindowFrameUnits>()?;
self.next_token();
if self.parse_keyword("BETWEEN") {
let start_bound = self.parse_window_frame_bound()?;
self.expect_keyword("AND")?;
let end_bound = Some(self.parse_window_frame_bound()?);
Some(WindowFrame {
units,
start_bound,
end_bound,
})
} else {
let start_bound = self.parse_window_frame_bound()?;
let end_bound = None;
Some(WindowFrame {
units,
start_bound,
end_bound,
})
}
}
Some(Token::RParen) => None,
unexpected => return self.expected("'ROWS', 'RANGE', 'GROUPS', or ')'", unexpected),
pub fn parse_window_frame(&mut self) -> Result<WindowFrame, ParserError> {
let units = match self.next_token() {
Some(Token::Word(w)) => w.keyword.parse::<WindowFrameUnits>()?,
unexpected => return self.expected("ROWS, RANGE, GROUPS", unexpected),
};
self.expect_token(&Token::RParen)?;
Ok(window_frame)
let (start_bound, end_bound) = if self.parse_keyword("BETWEEN") {
let start_bound = self.parse_window_frame_bound()?;
self.expect_keyword("AND")?;
let end_bound = Some(self.parse_window_frame_bound()?);
(start_bound, end_bound)
} else {
(self.parse_window_frame_bound()?, None)
};
Ok(WindowFrame {
units,
start_bound,
end_bound,
})
}
/// "CURRENT ROW" | ( (<positive number> | "UNBOUNDED") ("PRECEDING" | FOLLOWING) )