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Implement FROM-first selects (#1713)

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Armin Ronacher 2025-02-09 06:10:58 +01:00 • committed by GitHub
parent cad49232c1
commit 46cfcfe8f7
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13 changed files with 184 additions and 9 deletions
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52
src/parser/mod.rs
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@ -528,7 +528,7 @@ impl<'a> Parser<'a> {
Keyword::DESCRIBE => self.parse_explain(DescribeAlias::Describe),
Keyword::EXPLAIN => self.parse_explain(DescribeAlias::Explain),
Keyword::ANALYZE => self.parse_analyze(),
Keyword::SELECT | Keyword::WITH | Keyword::VALUES => {
Keyword::SELECT | Keyword::WITH | Keyword::VALUES | Keyword::FROM => {
self.prev_token();
self.parse_query().map(Statement::Query)
}
@ -10218,7 +10218,9 @@ impl<'a> Parser<'a> {
pub fn parse_query_body(&mut self, precedence: u8) -> Result<Box<SetExpr>, ParserError> {
// We parse the expression using a Pratt parser, as in `parse_expr()`.
// Start by parsing a restricted SELECT or a `(subquery)`:
let expr = if self.peek_keyword(Keyword::SELECT) {
let expr = if self.peek_keyword(Keyword::SELECT)
|| (self.peek_keyword(Keyword::FROM) && self.dialect.supports_from_first_select())
{
SetExpr::Select(self.parse_select().map(Box::new)?)
} else if self.consume_token(&Token::LParen) {
// CTEs are not allowed here, but the parser currently accepts them
@ -10317,6 +10319,39 @@ impl<'a> Parser<'a> {
/// Parse a restricted `SELECT` statement (no CTEs / `UNION` / `ORDER BY`)
pub fn parse_select(&mut self) -> Result<Select, ParserError> {
let mut from_first = None;
if self.dialect.supports_from_first_select() && self.peek_keyword(Keyword::FROM) {
let from_token = self.expect_keyword(Keyword::FROM)?;
let from = self.parse_table_with_joins()?;
if !self.peek_keyword(Keyword::SELECT) {
return Ok(Select {
select_token: AttachedToken(from_token),
distinct: None,
top: None,
top_before_distinct: false,
projection: vec![],
into: None,
from,
lateral_views: vec![],
prewhere: None,
selection: None,
group_by: GroupByExpr::Expressions(vec![], vec![]),
cluster_by: vec![],
distribute_by: vec![],
sort_by: vec![],
having: None,
named_window: vec![],
window_before_qualify: false,
qualify: None,
value_table_mode: None,
connect_by: None,
flavor: SelectFlavor::FromFirstNoSelect,
});
}
from_first = Some(from);
}
let select_token = self.expect_keyword(Keyword::SELECT)?;
let value_table_mode =
if dialect_of!(self is BigQueryDialect) && self.parse_keyword(Keyword::AS) {
@ -10371,10 +10406,12 @@ impl<'a> Parser<'a> {
// otherwise they may be parsed as an alias as part of the `projection`
// or `from`.
let from = if self.parse_keyword(Keyword::FROM) {
self.parse_table_with_joins()?
let (from, from_first) = if let Some(from) = from_first.take() {
(from, true)
} else if self.parse_keyword(Keyword::FROM) {
(self.parse_table_with_joins()?, false)
} else {
vec![]
(vec![], false)
};
let mut lateral_views = vec![];
@ -10506,6 +10543,11 @@ impl<'a> Parser<'a> {
qualify,
value_table_mode,
connect_by,
flavor: if from_first {
SelectFlavor::FromFirst
} else {
SelectFlavor::Standard
},
})
}