Add support for WITH FILL to OrderByExpr

ClickHouse supports the ORDER BY ... WITH FILL modifier:

https://clickhouse.com/docs/en/sql-reference/statements/select/order-by#order-by-expr-with-fill-modifier

WITH FILL itself supports a simple "from", "to", and "step" parameters,
and a more sophisticated INTERPOLATE option.

src/ast/mod.rs

@@ -43,14 +43,14 @@ pub use self::operator::{BinaryOperator, UnaryOperator};
 pub use self::query::{
     AfterMatchSkip, ConnectBy, Cte, CteAsMaterialized, Distinct, EmptyMatchesMode,
     ExceptSelectItem, ExcludeSelectItem, ExprWithAlias, Fetch, ForClause, ForJson, ForXml,
-    GroupByExpr, GroupByWithModifier, IdentWithAlias, IlikeSelectItem, Join, JoinConstraint,
+    GroupByExpr, GroupByWithModifier, IdentWithAlias, IlikeSelectItem, Interpolation, Join, JoinConstraint,
     JoinOperator, JsonTableColumn, JsonTableColumnErrorHandling, LateralView, LockClause, LockType,
     MatchRecognizePattern, MatchRecognizeSymbol, Measure, NamedWindowDefinition, NamedWindowExpr,
     NonBlock, Offset, OffsetRows, OrderByExpr, PivotValueSource, Query, RenameSelectItem,
     RepetitionQuantifier, ReplaceSelectElement, ReplaceSelectItem, RowsPerMatch, Select,
     SelectInto, SelectItem, SetExpr, SetOperator, SetQuantifier, SymbolDefinition, Table,
     TableAlias, TableFactor, TableVersion, TableWithJoins, Top, TopQuantity, ValueTableMode,
-    Values, WildcardAdditionalOptions, With,
+    Values, WildcardAdditionalOptions, With, WithFill,
 };
 pub use self::value::{
     escape_double_quote_string, escape_quoted_string, DateTimeField, DollarQuotedString,

src/ast/query.rs

@@ -1627,6 +1627,9 @@ pub struct OrderByExpr {
     pub asc: Option<bool>,
     /// Optional `NULLS FIRST` or `NULLS LAST`
     pub nulls_first: Option<bool>,
+    /// Optional: `WITH FILL`
+    /// Supported by [ClickHouse syntax]: <https://clickhouse.com/docs/en/sql-reference/statements/select/order-by#order-by-expr-with-fill-modifier>
+    pub with_fill: Option<WithFill>,
 }
 
 impl fmt::Display for OrderByExpr {
@@ -1642,6 +1645,58 @@ impl fmt::Display for OrderByExpr {
             Some(false) => write!(f, " NULLS LAST")?,
             None => (),
         }
+        if let Some(ref with_fill) = self.with_fill {
+            write!(f, " {}", with_fill)?
+        }
+        Ok(())
+    }
+}
+
+/// ClickHouse `WITH FILL` modifier for `ORDER BY` clause.
+#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+pub struct WithFill {
+    pub from: Option<Expr>,
+    pub to: Option<Expr>,
+    pub step: Option<Expr>,
+    pub interpolate: Vec<Interpolation>,
+}
+
+impl fmt::Display for WithFill {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "WITH FILL")?;
+        if let Some(ref from) = self.from {
+            write!(f, " FROM {}", from)?;
+        }
+        if let Some(ref to) = self.to {
+            write!(f, " TO {}", to)?;
+        }
+        if let Some(ref step) = self.step {
+            write!(f, " STEP {}", step)?;
+        }
+        if !self.interpolate.is_empty() {
+            write!(f, " INTERPOLATE ({})", display_comma_separated(&self.interpolate))?;
+        }
+        Ok(())
+    }
+}
+
+/// ClickHouse `INTERPOLATE` clause for use in `WITH FILL` modifier.
+#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+pub struct Interpolation {
+    pub column: Expr,
+    pub formula: Option<Expr>,
+}
+
+impl fmt::Display for Interpolation {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.column)?;
+        if let Some(ref formula) = self.formula {
+            write!(f, " AS {}", formula)?;
+        }
         Ok(())
     }
 }

src/keywords.rs

@@ -297,6 +297,7 @@ define_keywords!(
     FILE,
     FILES,
     FILE_FORMAT,
+    FILL,
     FILTER,
     FIRST,
     FIRST_VALUE,
@@ -382,6 +383,7 @@ define_keywords!(
     INT64,
     INT8,
     INTEGER,
+    INTERPOLATE,
     INTERSECT,
     INTERSECTION,
     INTERVAL,
@@ -678,6 +680,7 @@ define_keywords!(
     STDDEV_SAMP,
     STDIN,
     STDOUT,
+    STEP,
     STORAGE_INTEGRATION,
     STORED,
     STRICT,

src/parser/mod.rs

@@ -10408,13 +10408,70 @@ impl<'a> Parser<'a> {
             None
         };
 
+        let with_fill = if self.parse_keywords(&[Keyword::WITH, Keyword::FILL]) {
+            Some(self.parse_with_fill()?)
+        } else {
+            None
+        };
+
         Ok(OrderByExpr {
             expr,
             asc,
             nulls_first,
+            with_fill,
         })
     }
 
+    // Parse a WITH FILL clause (ClickHouse dialect)
+    // that follow the WITH FILL keywords in a ORDER BY clause
+    pub fn parse_with_fill(&mut self) -> Result<WithFill, ParserError> {
+        let from = if self.parse_keyword(Keyword::FROM) {
+            Some(self.parse_expr()?)
+        } else {
+            None
+        };
+
+        let to = if self.parse_keyword(Keyword::TO) {
+            Some(self.parse_expr()?)
+        } else {
+            None
+        };
+
+        let step = if self.parse_keyword(Keyword::STEP) {
+            Some(self.parse_expr()?)
+        } else {
+            None
+        };
+
+        let interpolate = if self.parse_keyword(Keyword::INTERPOLATE) && self.consume_token(&Token::LParen) {
+            let interpolations = self.parse_interpolations()?;
+            self.expect_token(&Token::RParen)?;
+            interpolations
+        } else {
+            vec![]
+        };
+
+        Ok(WithFill { from, to, step, interpolate })
+    }
+
+    // Parse a set of comma seperated INTERPOLATE expressions (ClickHouse dialect)
+    // that follow the INTERPOLATE keyword in a WITH FILL clause
+    pub fn parse_interpolations(&mut self) -> Result<Vec<Interpolation>, ParserError> {
+        self.parse_comma_separated(|p| p.parse_interpolation())
+    }
+
+
+    // Parse a INTERPOLATE expression (ClickHouse dialect)
+    pub fn parse_interpolation(&mut self) -> Result<Interpolation, ParserError> {
+        let column = self.parse_expr()?;
+        let formula = if self.parse_keyword(Keyword::AS) {
+            Some(self.parse_expr()?)
+        } else {
+            None
+        };
+        Ok(Interpolation { column, formula })
+    }
+
     /// Parse a TOP clause, MSSQL equivalent of LIMIT,
     /// that follows after `SELECT [DISTINCT]`.
     pub fn parse_top(&mut self) -> Result<Top, ParserError> {