Snowflake: Add support for Lambda functions

Author: yoavcloud

src/ast/mod.rs

@@ -1423,7 +1423,7 @@ impl fmt::Display for AccessExpr {
 #[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
 pub struct LambdaFunction {
     /// The parameters to the lambda function.
-    pub params: OneOrManyWithParens<Ident>,
+    pub params: OneOrManyWithParens<LambdaFunctionParameter>,
     /// The body of the lambda function.
     pub body: Box<Expr>,
     /// The syntax style used to write the lambda function.
@@ -1448,6 +1448,26 @@ impl fmt::Display for LambdaFunction {
     }
 }
 
+/// A parameter to a lambda function, optionally with a data type.
+#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+#[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
+pub struct LambdaFunctionParameter {
+    /// The name of the parameter
+    pub name: Ident,
+    /// The optional data type of the parameter
+    pub data_type: Option<DataType>,
+}
+
+impl fmt::Display for LambdaFunctionParameter {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match &self.data_type {
+            Some(dt) => write!(f, "{} {}", self.name, dt),
+            None => write!(f, "{}", self.name),
+        }
+    }
+}
+
 /// The syntax style for a lambda function.
 #[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash, Copy)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]

src/dialect/snowflake.rs

@@ -662,6 +662,11 @@ impl Dialect for SnowflakeDialect {
     fn supports_select_wildcard_rename(&self) -> bool {
         true
     }
+
+    /// See <https://docs.snowflake.com/en/user-guide/querying-semistructured#label-higher-order-functions>
+    fn supports_lambda_functions(&self) -> bool {
+        true
+    }
 }
 
 // Peeks ahead to identify tokens that are expected after

src/parser/mod.rs

@@ -1609,7 +1609,25 @@ impl<'a> Parser<'a> {
             Token::Arrow if self.dialect.supports_lambda_functions() => {
                 self.expect_token(&Token::Arrow)?;
                 Ok(Expr::Lambda(LambdaFunction {
-                    params: OneOrManyWithParens::One(w.to_ident(w_span)),
+                    params: OneOrManyWithParens::One(LambdaFunctionParameter {
+                        name: w.to_ident(w_span),
+                        data_type: None,
+                    }),
+                    body: Box::new(self.parse_expr()?),
+                    syntax: LambdaSyntax::Arrow,
+                }))
+            }
+            Token::Word(_)
+                if self.peek_nth_token(1).token == Token::Arrow
+                    && self.dialect.supports_lambda_functions() =>
+            {
+                let first_param = LambdaFunctionParameter {
+                    name: w.to_ident(self.peek_nth_token_ref(1).span),
+                    data_type: self.maybe_parse(|parser| parser.parse_data_type())?,
+                };
+                self.expect_token(&Token::Arrow)?;
+                Ok(Expr::Lambda(LambdaFunction {
+                    params: OneOrManyWithParens::One(first_param),
                     body: Box::new(self.parse_expr()?),
                     syntax: LambdaSyntax::Arrow,
                 }))
@@ -2195,7 +2213,12 @@ impl<'a> Parser<'a> {
             return Ok(None);
         }
         self.maybe_parse(|p| {
-            let params = p.parse_comma_separated(|p| p.parse_identifier())?;
+            let params = p.parse_comma_separated(|p| {
+                Ok(LambdaFunctionParameter {
+                    name: p.parse_identifier()?,
+                    data_type: None,
+                })
+            })?;
             p.expect_token(&Token::RParen)?;
             p.expect_token(&Token::Arrow)?;
             let expr = p.parse_expr()?;
@@ -2220,12 +2243,22 @@ impl<'a> Parser<'a> {
         // Parse the parameters: either a single identifier or comma-separated identifiers
         let params = if self.consume_token(&Token::LParen) {
             // Parenthesized parameters: (x, y)
-            let params = self.parse_comma_separated(|p| p.parse_identifier())?;
+            let params = self.parse_comma_separated(|p| {
+                Ok(LambdaFunctionParameter {
+                    name: p.parse_identifier()?,
+                    data_type: None,
+                })
+            })?;
             self.expect_token(&Token::RParen)?;
             OneOrManyWithParens::Many(params)
         } else {
             // Unparenthesized parameters: x or x, y
-            let params = self.parse_comma_separated(|p| p.parse_identifier())?;
+            let params = self.parse_comma_separated(|p| {
+                Ok(LambdaFunctionParameter {
+                    name: p.parse_identifier()?,
+                    data_type: None,
+                })
+            })?;
             if params.len() == 1 {
                 OneOrManyWithParens::One(params.into_iter().next().unwrap())
             } else {

tests/sqlparser_common.rs

@@ -15925,7 +15925,16 @@ fn test_lambdas() {
                     ]
                 ),
                 Expr::Lambda(LambdaFunction {
-                    params: OneOrManyWithParens::Many(vec![Ident::new("p1"), Ident::new("p2")]),
+                    params: OneOrManyWithParens::Many(vec![
+                        LambdaFunctionParameter {
+                            name: Ident::new("p1"),
+                            data_type: None
+                        },
+                        LambdaFunctionParameter {
+                            name: Ident::new("p2"),
+                            data_type: None
+                        }
+                    ]),
                     body: Box::new(Expr::Case {
                         case_token: AttachedToken::empty(),
                         end_token: AttachedToken::empty(),

tests/sqlparser_databricks.rs

@@ -72,7 +72,10 @@ fn test_databricks_exists() {
                     ]
                 ),
                 Expr::Lambda(LambdaFunction {
-                    params: OneOrManyWithParens::One(Ident::new("x")),
+                    params: OneOrManyWithParens::One(LambdaFunctionParameter {
+                        name: Ident::new("x"),
+                        data_type: None
+                    }),
                     body: Box::new(Expr::IsNull(Box::new(Expr::Identifier(Ident::new("x"))))),
                     syntax: LambdaSyntax::Arrow,
                 })
@@ -109,7 +112,16 @@ fn test_databricks_lambdas() {
                     ]
                 ),
                 Expr::Lambda(LambdaFunction {
-                    params: OneOrManyWithParens::Many(vec![Ident::new("p1"), Ident::new("p2")]),
+                    params: OneOrManyWithParens::Many(vec![
+                        LambdaFunctionParameter {
+                            name: Ident::new("p1"),
+                            data_type: None
+                        },
+                        LambdaFunctionParameter {
+                            name: Ident::new("p2"),
+                            data_type: None
+                        }
+                    ]),
                     body: Box::new(Expr::Case {
                         case_token: AttachedToken::empty(),
                         end_token: AttachedToken::empty(),

tests/sqlparser_snowflake.rs

@@ -4878,3 +4878,9 @@ fn test_truncate_table_if_exists() {
     snowflake().verified_stmt("TRUNCATE TABLE my_table");
     snowflake().verified_stmt("TRUNCATE IF EXISTS my_table");
 }
+
+#[test]
+fn test_snowflake_lambda() {
+    snowflake().verified_expr("TRANSFORM([1, 2, 3], a -> a * 2)");
+    snowflake().verified_expr("TRANSFORM([1, 2, 3], a INT -> a * 2)");
+}