Support DROP FUNCTION syntax (#752)

* drop function

* update  and  to Option

* fix review

* update

* fmt

src/ast/mod.rs

@@ -1268,6 +1268,14 @@ pub enum Statement {
         /// deleted along with the dropped table
         purge: bool,
     },
+    /// DROP Function
+    DropFunction {
+        if_exists: bool,
+        /// One or more function to drop
+        func_desc: Vec<DropFunctionDesc>,
+        /// `CASCADE` or `RESTRICT`
+        option: Option<ReferentialAction>,
+    },
     /// DECLARE - Declaring Cursor Variables
     ///
     /// Note: this is a PostgreSQL-specific statement,
@@ -1432,7 +1440,7 @@ pub enum Statement {
         or_replace: bool,
         temporary: bool,
         name: ObjectName,
-        args: Option<Vec<CreateFunctionArg>>,
+        args: Option<Vec<OperateFunctionArg>>,
         return_type: Option<DataType>,
         /// Optional parameters.
         params: CreateFunctionBody,
@@ -2284,6 +2292,22 @@ impl fmt::Display for Statement {
                 if *restrict { " RESTRICT" } else { "" },
                 if *purge { " PURGE" } else { "" }
             ),
+            Statement::DropFunction {
+                if_exists,
+                func_desc,
+                option,
+            } => {
+                write!(
+                    f,
+                    "DROP FUNCTION{} {}",
+                    if *if_exists { " IF EXISTS" } else { "" },
+                    display_comma_separated(func_desc),
+                )?;
+                if let Some(op) = option {
+                    write!(f, " {}", op)?;
+                }
+                Ok(())
+            }
             Statement::Discard { object_type } => {
                 write!(f, "DISCARD {object_type}", object_type = object_type)?;
                 Ok(())
@@ -3726,17 +3750,52 @@ impl fmt::Display for ContextModifier {
     }
 }
 
-/// Function argument in CREATE FUNCTION.
+/// Function describe in DROP FUNCTION.
 #[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
-pub struct CreateFunctionArg {
+pub enum DropFunctionOption {
+    Restrict,
+    Cascade,
+}
+
+impl fmt::Display for DropFunctionOption {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self {
+            DropFunctionOption::Restrict => write!(f, "RESTRICT "),
+            DropFunctionOption::Cascade => write!(f, "CASCADE  "),
+        }
+    }
+}
+
+/// Function describe in DROP FUNCTION.
+#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct DropFunctionDesc {
+    pub name: ObjectName,
+    pub args: Option<Vec<OperateFunctionArg>>,
+}
+
+impl fmt::Display for DropFunctionDesc {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        write!(f, "{}", self.name)?;
+        if let Some(args) = &self.args {
+            write!(f, "({})", display_comma_separated(args))?;
+        }
+        Ok(())
+    }
+}
+
+/// Function argument in CREATE OR DROP FUNCTION.
+#[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
+#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
+pub struct OperateFunctionArg {
     pub mode: Option<ArgMode>,
     pub name: Option<Ident>,
     pub data_type: DataType,
     pub default_expr: Option<Expr>,
 }
 
-impl CreateFunctionArg {
+impl OperateFunctionArg {
     /// Returns an unnamed argument.
     pub fn unnamed(data_type: DataType) -> Self {
         Self {
@@ -3758,7 +3817,7 @@ impl CreateFunctionArg {
     }
 }
 
-impl fmt::Display for CreateFunctionArg {
+impl fmt::Display for OperateFunctionArg {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         if let Some(mode) = &self.mode {
             write!(f, "{} ", mode)?;

src/parser.rs

@@ -2343,7 +2343,13 @@ impl<'a> Parser<'a> {
         } else if dialect_of!(self is PostgreSqlDialect) {
             let name = self.parse_object_name()?;
             self.expect_token(&Token::LParen)?;
-            let args = self.parse_comma_separated(Parser::parse_create_function_arg)?;
+            let args = if self.consume_token(&Token::RParen) {
+                self.prev_token();
+                None
+            } else {
+                Some(self.parse_comma_separated(Parser::parse_function_arg)?)
+            };
+
             self.expect_token(&Token::RParen)?;
 
             let return_type = if self.parse_keyword(Keyword::RETURNS) {
@@ -2358,7 +2364,7 @@ impl<'a> Parser<'a> {
                 or_replace,
                 temporary,
                 name,
-                args: Some(args),
+                args,
                 return_type,
                 params,
             })
@@ -2368,7 +2374,7 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn parse_create_function_arg(&mut self) -> Result<CreateFunctionArg, ParserError> {
+    fn parse_function_arg(&mut self) -> Result<OperateFunctionArg, ParserError> {
         let mode = if self.parse_keyword(Keyword::IN) {
             Some(ArgMode::In)
         } else if self.parse_keyword(Keyword::OUT) {
@@ -2394,7 +2400,7 @@ impl<'a> Parser<'a> {
         } else {
             None
         };
-        Ok(CreateFunctionArg {
+        Ok(OperateFunctionArg {
             mode,
             name,
             data_type,
@@ -2767,9 +2773,11 @@ impl<'a> Parser<'a> {
             ObjectType::Schema
         } else if self.parse_keyword(Keyword::SEQUENCE) {
             ObjectType::Sequence
+        } else if self.parse_keyword(Keyword::FUNCTION) {
+            return self.parse_drop_function();
         } else {
             return self.expected(
-                "TABLE, VIEW, INDEX, ROLE, SCHEMA, or SEQUENCE after DROP",
+                "TABLE, VIEW, INDEX, ROLE, SCHEMA, FUNCTION or SEQUENCE after DROP",
                 self.peek_token(),
             );
         };
@@ -2796,6 +2804,41 @@ impl<'a> Parser<'a> {
         })
     }
 
+    /// DROP FUNCTION [ IF EXISTS ] name [ ( [ [ argmode ] [ argname ] argtype [, ...] ] ) ] [, ...]
+    /// [ CASCADE | RESTRICT ]
+    fn parse_drop_function(&mut self) -> Result<Statement, ParserError> {
+        let if_exists = self.parse_keywords(&[Keyword::IF, Keyword::EXISTS]);
+        let func_desc = self.parse_comma_separated(Parser::parse_drop_function_desc)?;
+        let option = match self.parse_one_of_keywords(&[Keyword::CASCADE, Keyword::RESTRICT]) {
+            Some(Keyword::CASCADE) => Some(ReferentialAction::Cascade),
+            Some(Keyword::RESTRICT) => Some(ReferentialAction::Restrict),
+            _ => None,
+        };
+        Ok(Statement::DropFunction {
+            if_exists,
+            func_desc,
+            option,
+        })
+    }
+
+    fn parse_drop_function_desc(&mut self) -> Result<DropFunctionDesc, ParserError> {
+        let name = self.parse_object_name()?;
+
+        let args = if self.consume_token(&Token::LParen) {
+            if self.consume_token(&Token::RParen) {
+                None
+            } else {
+                let args = self.parse_comma_separated(Parser::parse_function_arg)?;
+                self.expect_token(&Token::RParen)?;
+                Some(args)
+            }
+        } else {
+            None
+        };
+
+        Ok(DropFunctionDesc { name, args })
+    }
+
     /// DECLARE name [ BINARY ] [ ASENSITIVE | INSENSITIVE ] [ [ NO ] SCROLL ]
     //     CURSOR [ { WITH | WITHOUT } HOLD ] FOR query
     pub fn parse_declare(&mut self) -> Result<Statement, ParserError> {

tests/sqlparser_postgres.rs

@@ -2348,8 +2348,8 @@ fn parse_create_function() {
             temporary: false,
             name: ObjectName(vec![Ident::new("add")]),
             args: Some(vec![
-                CreateFunctionArg::unnamed(DataType::Integer(None)),
+                OperateFunctionArg::unnamed(DataType::Integer(None)),
-                CreateFunctionArg::unnamed(DataType::Integer(None)),
+                OperateFunctionArg::unnamed(DataType::Integer(None)),
             ]),
             return_type: Some(DataType::Integer(None)),
             params: CreateFunctionBody {
@@ -2371,8 +2371,8 @@ fn parse_create_function() {
             temporary: false,
             name: ObjectName(vec![Ident::new("add")]),
             args: Some(vec![
-                CreateFunctionArg::with_name("a", DataType::Integer(None)),
+                OperateFunctionArg::with_name("a", DataType::Integer(None)),
-                CreateFunctionArg {
+                OperateFunctionArg {
                     mode: Some(ArgMode::In),
                     name: Some("b".into()),
                     data_type: DataType::Integer(None),
@@ -2400,7 +2400,7 @@ fn parse_create_function() {
             or_replace: true,
             temporary: false,
             name: ObjectName(vec![Ident::new("increment")]),
-            args: Some(vec![CreateFunctionArg::with_name(
+            args: Some(vec![OperateFunctionArg::with_name(
                 "i",
                 DataType::Integer(None)
             )]),
@@ -2417,3 +2417,93 @@ fn parse_create_function() {
         }
     );
 }
+
+#[test]
+fn parse_drop_function() {
+    let sql = "DROP FUNCTION IF EXISTS test_func";
+    assert_eq!(
+        pg().verified_stmt(sql),
+        Statement::DropFunction {
+            if_exists: true,
+            func_desc: vec![DropFunctionDesc {
+                name: ObjectName(vec![Ident {
+                    value: "test_func".to_string(),
+                    quote_style: None
+                }]),
+                args: None
+            }],
+            option: None
+        }
+    );
+
+    let sql = "DROP FUNCTION IF EXISTS test_func(a INTEGER, IN b INTEGER = 1)";
+    assert_eq!(
+        pg().verified_stmt(sql),
+        Statement::DropFunction {
+            if_exists: true,
+            func_desc: vec![DropFunctionDesc {
+                name: ObjectName(vec![Ident {
+                    value: "test_func".to_string(),
+                    quote_style: None
+                }]),
+                args: Some(vec![
+                    OperateFunctionArg::with_name("a", DataType::Integer(None)),
+                    OperateFunctionArg {
+                        mode: Some(ArgMode::In),
+                        name: Some("b".into()),
+                        data_type: DataType::Integer(None),
+                        default_expr: Some(Expr::Value(Value::Number("1".parse().unwrap(), false))),
+                    }
+                ]),
+            }],
+            option: None
+        }
+    );
+
+    let sql = "DROP FUNCTION IF EXISTS test_func1(a INTEGER, IN b INTEGER = 1), test_func2(a VARCHAR, IN b INTEGER = 1)";
+    assert_eq!(
+        pg().verified_stmt(sql),
+        Statement::DropFunction {
+            if_exists: true,
+            func_desc: vec![
+                DropFunctionDesc {
+                    name: ObjectName(vec![Ident {
+                        value: "test_func1".to_string(),
+                        quote_style: None
+                    }]),
+                    args: Some(vec![
+                        OperateFunctionArg::with_name("a", DataType::Integer(None)),
+                        OperateFunctionArg {
+                            mode: Some(ArgMode::In),
+                            name: Some("b".into()),
+                            data_type: DataType::Integer(None),
+                            default_expr: Some(Expr::Value(Value::Number(
+                                "1".parse().unwrap(),
+                                false
+                            ))),
+                        }
+                    ]),
+                },
+                DropFunctionDesc {
+                    name: ObjectName(vec![Ident {
+                        value: "test_func2".to_string(),
+                        quote_style: None
+                    }]),
+                    args: Some(vec![
+                        OperateFunctionArg::with_name("a", DataType::Varchar(None)),
+                        OperateFunctionArg {
+                            mode: Some(ArgMode::In),
+                            name: Some("b".into()),
+                            data_type: DataType::Integer(None),
+                            default_expr: Some(Expr::Value(Value::Number(
+                                "1".parse().unwrap(),
+                                false
+                            ))),
+                        }
+                    ]),
+                }
+            ],
+            option: None
+        }
+    );
+}