Named window frames (#881)

* after over clause, named window can be parsed with window ... as after having clause

* Lint errors are fixed

* Support for multiple windows

* fix lint errors

* simplifications

* rename function

* Rewrite named window search in functional style

* Test added and some minor changes

* Minor changes on tests and namings, and semantic check is removed

---------

Co-authored-by: Mustafa Akur <mustafa.akur@synnada.ai>
Co-authored-by: Mehmet Ozan Kabak <ozankabak@gmail.com>

src/ast/mod.rs

@@ -17,7 +17,7 @@ use alloc::{
     string::{String, ToString},
     vec::Vec,
 };
-use core::fmt;
+use core::fmt::{self, Display};
 
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
@@ -35,10 +35,10 @@ pub use self::ddl::{
 pub use self::operator::{BinaryOperator, UnaryOperator};
 pub use self::query::{
     Cte, Distinct, ExceptSelectItem, ExcludeSelectItem, Fetch, IdentWithAlias, Join,
-    JoinConstraint, JoinOperator, LateralView, LockClause, LockType, NonBlock, Offset, OffsetRows,
-    OrderByExpr, Query, RenameSelectItem, ReplaceSelectElement, ReplaceSelectItem, Select,
-    SelectInto, SelectItem, SetExpr, SetOperator, SetQuantifier, Table, TableAlias, TableFactor,
-    TableWithJoins, Top, Values, WildcardAdditionalOptions, With,
+    JoinConstraint, JoinOperator, LateralView, LockClause, LockType, NamedWindowDefinition,
+    NonBlock, Offset, OffsetRows, OrderByExpr, Query, RenameSelectItem, ReplaceSelectElement,
+    ReplaceSelectItem, Select, SelectInto, SelectItem, SetExpr, SetOperator, SetQuantifier, Table,
+    TableAlias, TableFactor, TableWithJoins, Top, Values, WildcardAdditionalOptions, With,
 };
 pub use self::value::{
     escape_quoted_string, DateTimeField, DollarQuotedString, TrimWhereField, Value,
@@ -930,6 +930,23 @@ impl fmt::Display for Expr {
     }
 }
 
+#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+pub enum WindowType {
+    WindowSpec(WindowSpec),
+    NamedWindow(Ident),
+}
+
+impl Display for WindowType {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            WindowType::WindowSpec(spec) => write!(f, "({})", spec),
+            WindowType::NamedWindow(name) => write!(f, "{}", name),
+        }
+    }
+}
+
 /// A window specification (i.e. `OVER (PARTITION BY .. ORDER BY .. etc.)`)
 #[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
@@ -3360,7 +3377,7 @@ impl fmt::Display for CloseCursor {
 pub struct Function {
     pub name: ObjectName,
     pub args: Vec<FunctionArg>,
-    pub over: Option<WindowSpec>,
+    pub over: Option<WindowType>,
     // aggregate functions may specify eg `COUNT(DISTINCT x)`
     pub distinct: bool,
     // Some functions must be called without trailing parentheses, for example Postgres
@@ -3409,7 +3426,7 @@ impl fmt::Display for Function {
             )?;
 
             if let Some(o) = &self.over {
-                write!(f, " OVER ({o})")?;
+                write!(f, " OVER {o}")?;
             }
         }
 

src/ast/query.rs

@@ -216,6 +216,8 @@ pub struct Select {
     pub sort_by: Vec<Expr>,
     /// HAVING
     pub having: Option<Expr>,
+    /// WINDOW AS
+    pub named_window: Vec<NamedWindowDefinition>,
     /// QUALIFY (Snowflake)
     pub qualify: Option<Expr>,
 }
@@ -269,6 +271,9 @@ impl fmt::Display for Select {
         if let Some(ref having) = self.having {
             write!(f, " HAVING {having}")?;
         }
+        if !self.named_window.is_empty() {
+            write!(f, " WINDOW {}", display_comma_separated(&self.named_window))?;
+        }
         if let Some(ref qualify) = self.qualify {
             write!(f, " QUALIFY {qualify}")?;
         }
@@ -311,6 +316,17 @@ impl fmt::Display for LateralView {
     }
 }
 
+#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+pub struct NamedWindowDefinition(pub Ident, pub WindowSpec);
+
+impl fmt::Display for NamedWindowDefinition {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{} AS ({})", self.0, self.1)
+    }
+}
+
 #[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]

src/keywords.rs

@@ -688,6 +688,7 @@ pub const RESERVED_FOR_TABLE_ALIAS: &[Keyword] = &[
     Keyword::OUTER,
     Keyword::SET,
     Keyword::QUALIFY,
+    Keyword::WINDOW,
 ];
 
 /// Can't be used as a column alias, so that `SELECT <expr> alias`

src/parser.rs

@@ -884,32 +884,12 @@ impl<'a> Parser<'a> {
         let distinct = self.parse_all_or_distinct()?.is_some();
         let (args, order_by) = self.parse_optional_args_with_orderby()?;
         let over = if self.parse_keyword(Keyword::OVER) {
-            // TBD: support window names (`OVER mywin`) in place of inline specification
-            self.expect_token(&Token::LParen)?;
-            let partition_by = if self.parse_keywords(&[Keyword::PARTITION, Keyword::BY]) {
-                // a list of possibly-qualified column names
-                self.parse_comma_separated(Parser::parse_expr)?
+            if self.consume_token(&Token::LParen) {
+                let window_spec = self.parse_window_spec()?;
+                Some(WindowType::WindowSpec(window_spec))
             } else {
-                vec![]
-            };
-            let order_by = if self.parse_keywords(&[Keyword::ORDER, Keyword::BY]) {
-                self.parse_comma_separated(Parser::parse_order_by_expr)?
-            } else {
-                vec![]
-            };
-            let window_frame = if !self.consume_token(&Token::RParen) {
-                let window_frame = self.parse_window_frame()?;
-                self.expect_token(&Token::RParen)?;
-                Some(window_frame)
-            } else {
-                None
-            };
-
-            Some(WindowSpec {
-                partition_by,
-                order_by,
-                window_frame,
-            })
+                Some(WindowType::NamedWindow(self.parse_identifier()?))
+            }
         } else {
             None
         };
@@ -5367,6 +5347,12 @@ impl<'a> Parser<'a> {
             None
         };
 
+        let named_windows = if self.parse_keyword(Keyword::WINDOW) {
+            self.parse_comma_separated(Parser::parse_named_window)?
+        } else {
+            vec![]
+        };
+
         let qualify = if self.parse_keyword(Keyword::QUALIFY) {
             Some(self.parse_expr()?)
         } else {
@@ -5386,6 +5372,7 @@ impl<'a> Parser<'a> {
             distribute_by,
             sort_by,
             having,
+            named_window: named_windows,
             qualify,
         })
     }
@@ -7033,6 +7020,39 @@ impl<'a> Parser<'a> {
     pub fn index(&self) -> usize {
         self.index
     }
+
+    pub fn parse_named_window(&mut self) -> Result<NamedWindowDefinition, ParserError> {
+        let ident = self.parse_identifier()?;
+        self.expect_keyword(Keyword::AS)?;
+        self.expect_token(&Token::LParen)?;
+        let window_spec = self.parse_window_spec()?;
+        Ok(NamedWindowDefinition(ident, window_spec))
+    }
+
+    pub fn parse_window_spec(&mut self) -> Result<WindowSpec, ParserError> {
+        let partition_by = if self.parse_keywords(&[Keyword::PARTITION, Keyword::BY]) {
+            self.parse_comma_separated(Parser::parse_expr)?
+        } else {
+            vec![]
+        };
+        let order_by = if self.parse_keywords(&[Keyword::ORDER, Keyword::BY]) {
+            self.parse_comma_separated(Parser::parse_order_by_expr)?
+        } else {
+            vec![]
+        };
+        let window_frame = if !self.consume_token(&Token::RParen) {
+            let window_frame = self.parse_window_frame()?;
+            self.expect_token(&Token::RParen)?;
+            Some(window_frame)
+        } else {
+            None
+        };
+        Ok(WindowSpec {
+            partition_by,
+            order_by,
+            window_frame,
+        })
+    }
 }
 
 impl Word {