BigQuery: Fix column identifier reserved keywords list

Parser currently uses the same `RESERVED_FOR_COLUMN_ALIAS` keywords
list to avoid lookahead when parsing column identifiers. This
assumed that all listed keywords were reservered across all dialects
which isn't the case.
So that the following valid BigQuery statement previously failed
due to `OFFSET` being flagged as a keyword.
```sql
SELECT 1, OFFSET FROM T
```
This updates the parser to support dialect specific
`RESERVED_FOR_COLUMN_ALIAS` list

Author: iffyio

src/dialect/bigquery.rs

@@ -16,6 +16,27 @@
 // under the License.
 
 use crate::dialect::Dialect;
+use crate::keywords::Keyword;
+
+/// These keywords are disallowed as column identifiers. Such that
+/// `SELECT 5 AS <col> FROM T` is rejected by BigQuery.
+const RESERVED_FOR_COLUMN_ALIAS: &[Keyword] = &[
+    Keyword::WITH,
+    Keyword::SELECT,
+    Keyword::WHERE,
+    Keyword::GROUP,
+    Keyword::HAVING,
+    Keyword::ORDER,
+    Keyword::LATERAL,
+    Keyword::LIMIT,
+    Keyword::FETCH,
+    Keyword::UNION,
+    Keyword::EXCEPT,
+    Keyword::INTERSECT,
+    Keyword::FROM,
+    Keyword::INTO,
+    Keyword::END,
+];
 
 /// A [`Dialect`] for [Google Bigquery](https://cloud.google.com/bigquery/)
 #[derive(Debug, Default)]
@@ -82,4 +103,8 @@ impl Dialect for BigQueryDialect {
     fn supports_timestamp_versioning(&self) -> bool {
         true
     }
+
+    fn get_reserved_keywords_for_column_identifier(&self) -> &'static [Keyword] {
+        RESERVED_FOR_COLUMN_ALIAS
+    }
 }

src/dialect/mod.rs

@@ -781,7 +781,7 @@ pub trait Dialect: Debug + Any {
         keywords::RESERVED_FOR_IDENTIFIER.contains(&kw)
     }
 
-    // Returns reserved keywords when looking to parse a [TableFactor].
+    /// Returns reserved keywords when looking to parse a [TableFactor].
     /// See [Self::supports_from_trailing_commas]
     fn get_reserved_keywords_for_table_factor(&self) -> &[Keyword] {
         keywords::RESERVED_FOR_TABLE_FACTOR
@@ -821,11 +821,24 @@ pub trait Dialect: Debug + Any {
         false
     }
 
+    /// Returns reserved keywords when looking to parse column
+    /// identifiers.
+    /// i.e. (unquoted) words that may not be used as column identifiers
+    /// for the dialect.
+    /// For example given: `SELECT <col> AS <alias> FROM T`. The returned
+    /// keywords are not allowed in `<col>` and `<alias>`
+    fn get_reserved_keywords_for_column_identifier(&self) -> &'static [Keyword] {
+        keywords::RESERVED_FOR_COLUMN_ALIAS
+    }
+
     /// Returns true if the specified keyword should be parsed as a select item alias.
     /// When explicit is true, the keyword is preceded by an `AS` word. Parser is provided
     /// to enable looking ahead if needed.
     fn is_select_item_alias(&self, explicit: bool, kw: &Keyword, _parser: &mut Parser) -> bool {
-        explicit || !keywords::RESERVED_FOR_COLUMN_ALIAS.contains(kw)
+        explicit
+            || !self
+                .get_reserved_keywords_for_column_identifier()
+                .contains(kw)
     }
 
     /// Returns true if the specified keyword should be parsed as a table factor alias.

src/parser/mod.rs

@@ -3989,7 +3989,8 @@ impl<'a> Parser<'a> {
         trailing_commas: bool,
         reserved_keywords: Option<&[Keyword]>,
     ) -> bool {
-        let reserved_keywords = reserved_keywords.unwrap_or(keywords::RESERVED_FOR_COLUMN_ALIAS);
+        let reserved_keywords = reserved_keywords
+            .unwrap_or_else(|| self.dialect.get_reserved_keywords_for_column_identifier());
         if !self.consume_token(&Token::Comma) {
             true
         } else if trailing_commas {
@@ -11153,7 +11154,9 @@ impl<'a> Parser<'a> {
             };
 
             let with_offset_alias = if with_offset {
-                match self.parse_optional_alias(keywords::RESERVED_FOR_COLUMN_ALIAS) {
+                match self.parse_optional_alias(
+                    self.dialect.get_reserved_keywords_for_column_identifier(),
+                ) {
                     Ok(Some(alias)) => Some(alias),
                     Ok(None) => None,
                     Err(e) => return Err(e),

tests/sqlparser_bigquery.rs

@@ -213,6 +213,15 @@ fn parse_raw_literal() {
     );
 }
 
+#[test]
+fn parse_big_query_non_reserved_column_alias() {
+    let sql = r#"SELECT OFFSET, EXPLAIN, ANALYZE, SORT, TOP, VIEW FROM T"#;
+    bigquery().verified_stmt(sql);
+
+    let sql = r#"SELECT 1 AS OFFSET, 2 AS EXPLAIN, 3 AS ANALYZE FROM T"#;
+    bigquery().verified_stmt(sql);
+}
+
 #[test]
 fn parse_delete_statement() {
     let sql = "DELETE \"table\" WHERE 1";

tests/sqlparser_common.rs

@@ -253,8 +253,15 @@ fn parse_insert_default_values() {
 
 #[test]
 fn parse_insert_select_returning() {
-    verified_stmt("INSERT INTO t SELECT 1 RETURNING 2");
-    let stmt = verified_stmt("INSERT INTO t SELECT x RETURNING x AS y");
+    // Dialects that support `RETURNING` as a column identifier do
+    // not support this syntax.
+    let dialects = all_dialects_where(|d| {
+        d.get_reserved_keywords_for_column_identifier()
+            .contains(&Keyword::RETURNING)
+    });
+
+    dialects.verified_stmt("INSERT INTO t SELECT 1 RETURNING 2");
+    let stmt = dialects.verified_stmt("INSERT INTO t SELECT x RETURNING x AS y");
     match stmt {
         Statement::Insert(Insert {
             returning: Some(ret),
@@ -6897,9 +6904,6 @@ fn parse_union_except_intersect_minus() {
     verified_stmt("SELECT 1 EXCEPT SELECT 2");
     verified_stmt("SELECT 1 EXCEPT ALL SELECT 2");
     verified_stmt("SELECT 1 EXCEPT DISTINCT SELECT 1");
-    verified_stmt("SELECT 1 MINUS SELECT 2");
-    verified_stmt("SELECT 1 MINUS ALL SELECT 2");
-    verified_stmt("SELECT 1 MINUS DISTINCT SELECT 1");
     verified_stmt("SELECT 1 INTERSECT SELECT 2");
     verified_stmt("SELECT 1 INTERSECT ALL SELECT 2");
     verified_stmt("SELECT 1 INTERSECT DISTINCT SELECT 1");
@@ -6918,6 +6922,16 @@ fn parse_union_except_intersect_minus() {
     verified_stmt("SELECT 1 AS x, 2 AS y INTERSECT BY NAME SELECT 9 AS y, 8 AS x");
     verified_stmt("SELECT 1 AS x, 2 AS y INTERSECT ALL BY NAME SELECT 9 AS y, 8 AS x");
     verified_stmt("SELECT 1 AS x, 2 AS y INTERSECT DISTINCT BY NAME SELECT 9 AS y, 8 AS x");
+
+    // Dialects that support `MINUS` as column identifier
+    // do not support `MINUS` as a set operator.
+    let dialects = all_dialects_where(|d| {
+        d.get_reserved_keywords_for_column_identifier()
+            .contains(&Keyword::MINUS)
+    });
+    dialects.verified_stmt("SELECT 1 MINUS SELECT 2");
+    dialects.verified_stmt("SELECT 1 MINUS ALL SELECT 2");
+    dialects.verified_stmt("SELECT 1 MINUS DISTINCT SELECT 1");
 }
 
 #[test]
@@ -7594,19 +7608,28 @@ fn parse_invalid_subquery_without_parens() {
 
 #[test]
 fn parse_offset() {
+    // Dialects that support `OFFSET` as column identifiers
+    // don't support this syntax.
+    let dialects = all_dialects_where(|d| {
+        d.get_reserved_keywords_for_column_identifier()
+            .contains(&Keyword::OFFSET)
+    });
+
     let expect = Some(Offset {
         value: Expr::Value(number("2")),
         rows: OffsetRows::Rows,
     });
-    let ast = verified_query("SELECT foo FROM bar OFFSET 2 ROWS");
+    let ast = dialects.verified_query("SELECT foo FROM bar OFFSET 2 ROWS");
     assert_eq!(ast.offset, expect);
-    let ast = verified_query("SELECT foo FROM bar WHERE foo = 4 OFFSET 2 ROWS");
+    let ast = dialects.verified_query("SELECT foo FROM bar WHERE foo = 4 OFFSET 2 ROWS");
     assert_eq!(ast.offset, expect);
-    let ast = verified_query("SELECT foo FROM bar ORDER BY baz OFFSET 2 ROWS");
+    let ast = dialects.verified_query("SELECT foo FROM bar ORDER BY baz OFFSET 2 ROWS");
     assert_eq!(ast.offset, expect);
-    let ast = verified_query("SELECT foo FROM bar WHERE foo = 4 ORDER BY baz OFFSET 2 ROWS");
+    let ast =
+        dialects.verified_query("SELECT foo FROM bar WHERE foo = 4 ORDER BY baz OFFSET 2 ROWS");
     assert_eq!(ast.offset, expect);
-    let ast = verified_query("SELECT foo FROM (SELECT * FROM bar OFFSET 2 ROWS) OFFSET 2 ROWS");
+    let ast =
+        dialects.verified_query("SELECT foo FROM (SELECT * FROM bar OFFSET 2 ROWS) OFFSET 2 ROWS");
     assert_eq!(ast.offset, expect);
     match *ast.body {
         SetExpr::Select(s) => match only(s.from).relation {
@@ -7617,23 +7640,23 @@ fn parse_offset() {
         },
         _ => panic!("Test broke"),
     }
-    let ast = verified_query("SELECT 'foo' OFFSET 0 ROWS");
+    let ast = dialects.verified_query("SELECT 'foo' OFFSET 0 ROWS");
     assert_eq!(
         ast.offset,
         Some(Offset {
             value: Expr::Value(number("0")),
             rows: OffsetRows::Rows,
         })
     );
-    let ast = verified_query("SELECT 'foo' OFFSET 1 ROW");
+    let ast = dialects.verified_query("SELECT 'foo' OFFSET 1 ROW");
     assert_eq!(
         ast.offset,
         Some(Offset {
             value: Expr::Value(number("1")),
             rows: OffsetRows::Row,
         })
     );
-    let ast = verified_query("SELECT 'foo' OFFSET 1");
+    let ast = dialects.verified_query("SELECT 'foo' OFFSET 1");
     assert_eq!(
         ast.offset,
         Some(Offset {