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Support table aliases without AS (7/8)

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...as in `FROM foo bar WHERE bar.x > 1`.

To avoid ambiguity as to whether a token is an alias or a keyword, we
maintain a blacklist of keywords, that can follow a "table factor", to
prevent parsing them as an alias. This "context-specific reserved
keyword" approach lets us accept more SQL that's valid in some dialects,
than a list of globally reserved keywords. Also some dialects (e.g.
Oracle) apparently don't reserve some keywords (like JOIN), while
presumably they won't accept them as an alias (`FROM foo JOIN` meaning
`FROM foo AS JOIN`).
This commit is contained in:
Nickolay Ponomarev 2019-01-21 01:28:59 +03:00
parent 536fa6e428
commit 76ec175d20
3 changed files with 36 additions and 11 deletions
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12
src/sqlparser.rs
View file

@ -14,6 +14,7 @@
//! SQL Parser
use super::dialect::keywords;
use super::dialect::Dialect;
use super::sqlast::*;
use super::sqltokenizer::*;
@ -950,13 +951,18 @@ impl Parser {
/// `SELECT ... FROM t1 foo, t2 bar`, `SELECT ... FROM (...) AS bar`
pub fn parse_optional_alias(
&mut self,
reserved_kwds: &[&str],
) -> Result<Option<SQLIdent>, ParserError> {
let after_as = self.parse_keyword("AS");
let maybe_alias = self.next_token();
match maybe_alias {
// Accept any identifier after `AS` (though many dialects have restrictions on
// keywords that may appear here).
Some(Token::SQLWord(ref w)) if after_as =>
// keywords that may appear here). If there's no `AS`: don't parse keywords,
// which may start a construct allowed in this position, to be parsed as aliases.
// (For example, in `FROM t1 JOIN` the `JOIN` will always be parsed as a keyword,
// not an alias.)
Some(Token::SQLWord(ref w))
if after_as || !reserved_kwds.contains(&w.keyword.as_str()) =>
{
// have to clone here until #![feature(bind_by_move_pattern_guards)] is enabled by default
Ok(Some(w.value.clone()))
@ -1157,7 +1163,7 @@ impl Parser {
} else {
self.parse_compound_identifier(&Token::Period)?
};
let alias = self.parse_optional_alias()?;
let alias = self.parse_optional_alias(keywords::RESERVED_FOR_TABLE_ALIAS)?;
Ok(ASTNode::TableFactor {
relation: Box::new(relation),
alias,