Support named windows in OVER (window_definition) clause (#1166)

Co-authored-by: Andrew Lamb <andrew@nerdnetworks.org>

src/ast/mod.rs

@@ -1246,11 +1246,19 @@ impl Display for WindowType {
     }
 }
 
-/// A window specification (i.e. `OVER (PARTITION BY .. ORDER BY .. etc.)`)
+/// A window specification (i.e. `OVER ([window_name] PARTITION BY .. ORDER BY .. etc.)`)
 #[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
 pub struct WindowSpec {
+    /// Optional window name.
+    ///
+    /// You can find it at least in [MySQL][1], [BigQuery][2], [PostgreSQL][3]
+    ///
+    /// [1]: https://dev.mysql.com/doc/refman/8.0/en/window-functions-named-windows.html
+    /// [2]: https://cloud.google.com/bigquery/docs/reference/standard-sql/window-function-calls
+    /// [3]: https://www.postgresql.org/docs/current/sql-expressions.html#SYNTAX-WINDOW-FUNCTIONS
+    pub window_name: Option<Ident>,
     /// `OVER (PARTITION BY ...)`
     pub partition_by: Vec<Expr>,
     /// `OVER (ORDER BY ...)`
@@ -1262,7 +1270,12 @@ pub struct WindowSpec {
 impl fmt::Display for WindowSpec {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         let mut delim = "";
+        if let Some(window_name) = &self.window_name {
+            delim = " ";
+            write!(f, "{window_name}")?;
+        }
         if !self.partition_by.is_empty() {
+            f.write_str(delim)?;
             delim = " ";
             write!(
                 f,

src/parser/mod.rs

@@ -9528,6 +9528,13 @@ impl<'a> Parser<'a> {
     }
 
     pub fn parse_window_spec(&mut self) -> Result<WindowSpec, ParserError> {
+        let window_name = match self.peek_token().token {
+            Token::Word(word) if word.keyword == Keyword::NoKeyword => {
+                self.maybe_parse(|parser| parser.parse_identifier(false))
+            }
+            _ => None,
+        };
+
         let partition_by = if self.parse_keywords(&[Keyword::PARTITION, Keyword::BY]) {
             self.parse_comma_separated(Parser::parse_expr)?
         } else {
@@ -9538,6 +9545,7 @@ impl<'a> Parser<'a> {
         } else {
             vec![]
         };
+
         let window_frame = if !self.consume_token(&Token::RParen) {
             let window_frame = self.parse_window_frame()?;
             self.expect_token(&Token::RParen)?;
@@ -9546,6 +9554,7 @@ impl<'a> Parser<'a> {
             None
         };
         Ok(WindowSpec {
+            window_name,
             partition_by,
             order_by,
             window_frame,

tests/sqlparser_common.rs

@@ -2062,6 +2062,7 @@ fn parse_select_qualify() {
                 null_treatment: None,
                 filter: None,
                 over: Some(WindowType::WindowSpec(WindowSpec {
+                    window_name: None,
                     partition_by: vec![Expr::Identifier(Ident::new("p"))],
                     order_by: vec![OrderByExpr {
                         expr: Expr::Identifier(Ident::new("o")),
@@ -4122,7 +4123,10 @@ fn parse_window_functions() {
                GROUPS BETWEEN 1 PRECEDING AND 1 FOLLOWING) \
                FROM foo";
     let select = verified_only_select(sql);
-    assert_eq!(7, select.projection.len());
+
+    const EXPECTED_PROJ_QTY: usize = 7;
+    assert_eq!(EXPECTED_PROJ_QTY, select.projection.len());
+
     assert_eq!(
         &Expr::Function(Function {
             name: ObjectName(vec![Ident::new("row_number")]),
@@ -4130,6 +4134,7 @@ fn parse_window_functions() {
             null_treatment: None,
             filter: None,
             over: Some(WindowType::WindowSpec(WindowSpec {
+                window_name: None,
                 partition_by: vec![],
                 order_by: vec![OrderByExpr {
                     expr: Expr::Identifier(Ident::new("dt")),
@@ -4144,6 +4149,66 @@ fn parse_window_functions() {
         }),
         expr_from_projection(&select.projection[0])
     );
+
+    for i in 0..EXPECTED_PROJ_QTY {
+        assert!(matches!(
+            expr_from_projection(&select.projection[i]),
+            Expr::Function(Function {
+                over: Some(WindowType::WindowSpec(WindowSpec {
+                    window_name: None,
+                    ..
+                })),
+                ..
+            })
+        ));
+    }
+}
+
+#[test]
+fn parse_named_window_functions() {
+    let supported_dialects = TestedDialects {
+        dialects: vec![
+            Box::new(GenericDialect {}),
+            Box::new(PostgreSqlDialect {}),
+            Box::new(MySqlDialect {}),
+            Box::new(BigQueryDialect {}),
+        ],
+        options: None,
+    };
+
+    let sql = "SELECT row_number() OVER (w ORDER BY dt DESC), \
+               sum(foo) OVER (win PARTITION BY a, b ORDER BY c, d \
+               ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) \
+               FROM foo \
+               WINDOW w AS (PARTITION BY x), win AS (ORDER BY y)";
+    supported_dialects.verified_stmt(sql);
+
+    let select = verified_only_select(sql);
+
+    const EXPECTED_PROJ_QTY: usize = 2;
+    assert_eq!(EXPECTED_PROJ_QTY, select.projection.len());
+
+    const EXPECTED_WIN_NAMES: [&str; 2] = ["w", "win"];
+    for (i, win_name) in EXPECTED_WIN_NAMES.iter().enumerate() {
+        assert!(matches!(
+            expr_from_projection(&select.projection[i]),
+            Expr::Function(Function {
+                over: Some(WindowType::WindowSpec(WindowSpec {
+                    window_name: Some(Ident { value, .. }),
+                    ..
+                })),
+                ..
+            }) if value == win_name
+        ));
+    }
+
+    let sql = "SELECT \
+        FIRST_VALUE(x) OVER (w ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS first, \
+        FIRST_VALUE(x) OVER (ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS last, \
+        SUM(y) OVER (win PARTITION BY x) AS last \
+        FROM EMPLOYEE \
+        WINDOW w AS (PARTITION BY x), win AS (w ORDER BY y)";
+    supported_dialects.verified_stmt(sql);
 }
 
 #[test]
@@ -4244,6 +4309,7 @@ fn test_parse_named_window() {
                     quote_style: None,
                 },
                 WindowSpec {
+                    window_name: None,
                     partition_by: vec![],
                     order_by: vec![OrderByExpr {
                         expr: Expr::Identifier(Ident {
@@ -4262,6 +4328,7 @@ fn test_parse_named_window() {
                     quote_style: None,
                 },
                 WindowSpec {
+                    window_name: None,
                     partition_by: vec![Expr::Identifier(Ident {
                         value: "C11".to_string(),
                         quote_style: None,

tests/sqlparser_sqlite.rs

@@ -446,6 +446,7 @@ fn parse_window_function_with_filter() {
                 ))],
                 null_treatment: None,
                 over: Some(WindowType::WindowSpec(WindowSpec {
+                    window_name: None,
                     partition_by: vec![],
                     order_by: vec![],
                     window_frame: None,