Add Expr::Tuple and parsing support, remove special case in DISTINCT clause

src/ast/mod.rs

@@ -284,6 +284,8 @@ pub enum Expr {
     Cube(Vec<Vec<Expr>>),
     /// The `ROLLUP` expr.
     Rollup(Vec<Vec<Expr>>),
+    /// ROW / TUPLE a single value, such as `SELECT (1, 2)`
+    Tuple(Vec<Expr>),
 }
 
 impl fmt::Display for Expr {
@@ -445,6 +447,9 @@ impl fmt::Display for Expr {
 
                 write!(f, ")")
             }
+            Expr::Tuple(exprs) => {
+                write!(f, "({})", display_comma_separated(exprs))
+            }
         }
     }
 }

src/parser.rs

@@ -494,7 +494,12 @@ impl<'a> Parser<'a> {
                         self.prev_token();
                         Expr::Subquery(Box::new(self.parse_query()?))
                     } else {
-                        Expr::Nested(Box::new(self.parse_expr()?))
+                        let exprs = self.parse_comma_separated(Parser::parse_expr)?;
+                        match exprs.len() {
+                            0 => unreachable!(), // parse_comma_separated ensures 1 or more
+                            1 => Expr::Nested(Box::new(exprs.into_iter().next().unwrap())),
+                            _ => Expr::Tuple(exprs),
+                        }
                     };
                 self.expect_token(&Token::RParen)?;
                 Ok(expr)
@@ -2680,19 +2685,8 @@ impl<'a> Parser<'a> {
             None
         };
 
-        // Not Sure if Top should be cheked here as well. Trino doesn't support TOP.
-        let is_l_paren = if distinct {
-            self.consume_token(&Token::LParen)
-        } else {
-            false
-        };
-
         let projection = self.parse_comma_separated(Parser::parse_select_item)?;
 
-        if is_l_paren && !self.consume_token(&Token::RParen) {
-            return self.expected(")", self.peek_token());
-        }
-
         // Note that for keywords to be properly handled here, they need to be
         // added to `RESERVED_FOR_COLUMN_ALIAS` / `RESERVED_FOR_TABLE_ALIAS`,
         // otherwise they may be parsed as an alias as part of the `projection`

tests/sqlparser_common.rs

@@ -332,7 +332,6 @@ fn parse_select_distinct_two_fields() {
     let sql = "SELECT DISTINCT name, id FROM customer";
     let select = verified_only_select(sql);
     assert!(select.distinct);
-    one_statement_parses_to("SELECT DISTINCT (name, id) FROM customer", sql);
     assert_eq!(
         &SelectItem::UnnamedExpr(Expr::Identifier(Ident::new("name"))),
         &select.projection[0]
@@ -343,6 +342,19 @@ fn parse_select_distinct_two_fields() {
     );
 }
 
+#[test]
+fn parse_select_distinct_tuple() {
+    let sql = "SELECT DISTINCT (name, id) FROM customer";
+    let select = verified_only_select(sql);
+    assert_eq!(
+        &vec![SelectItem::UnnamedExpr(Expr::Tuple(vec![
+            Expr::Identifier(Ident::new("name")),
+            Expr::Identifier(Ident::new("id")),
+        ]))],
+        &select.projection
+    );
+}
+
 #[test]
 fn parse_select_distinct_missing_paren() {
     let result = parse_sql_statements("SELECT DISTINCT (name, id FROM customer");
@@ -1033,6 +1045,44 @@ fn parse_between_with_expr() {
     )
 }
 
+#[test]
+fn parse_tuples() {
+    let sql = "SELECT (1, 2), (1), ('foo', 3, baz)";
+    let select = verified_only_select(sql);
+    assert_eq!(
+        vec![
+            SelectItem::UnnamedExpr(Expr::Tuple(vec![
+                Expr::Value(number("1")),
+                Expr::Value(number("2"))
+            ])),
+            SelectItem::UnnamedExpr(Expr::Nested(Box::new(Expr::Value(number("1"))))),
+            SelectItem::UnnamedExpr(Expr::Tuple(vec![
+                Expr::Value(Value::SingleQuotedString("foo".into())),
+                Expr::Value(number("3")),
+                Expr::Identifier(Ident::new("baz"))
+            ]))
+        ],
+        select.projection
+    );
+}
+
+#[test]
+fn parse_tuple_invalid() {
+    let sql = "select (1";
+    let res = parse_sql_statements(sql);
+    assert_eq!(
+        ParserError::ParserError("Expected ), found: EOF".to_string()),
+        res.unwrap_err()
+    );
+
+    let sql = "select (), 2";
+    let res = parse_sql_statements(sql);
+    assert_eq!(
+        ParserError::ParserError("Expected an expression:, found: )".to_string()),
+        res.unwrap_err()
+    );
+}
+
 #[test]
 fn parse_select_order_by() {
     fn chk(sql: &str) {
@@ -1121,6 +1171,12 @@ fn parse_select_group_by() {
         ],
         select.group_by
     );
+
+    // Tuples can also be in the set
+    one_statement_parses_to(
+        "SELECT id, fname, lname FROM customer GROUP BY (lname, fname)",
+        "SELECT id, fname, lname FROM customer GROUP BY (lname, fname)",
+    );
 }
 
 #[test]