Add RETURNS TABLE() support for CREATE FUNCTION in Postgresql (#1687)

Co-authored-by: Ifeanyi Ubah <ify1992@yahoo.com>

src/ast/data_type.rs

@@ -45,6 +45,10 @@ pub enum EnumMember {
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
 #[cfg_attr(feature = "visitor", derive(Visit, VisitMut))]
 pub enum DataType {
+    /// Table type in [postgresql]. e.g. CREATE FUNCTION RETURNS TABLE(...)
+    ///
+    /// [postgresql]: https://www.postgresql.org/docs/15/sql-createfunction.html
+    Table(Vec<ColumnDef>),
     /// Fixed-length character type e.g. CHARACTER(10)
     Character(Option<CharacterLength>),
     /// Fixed-length char type e.g. CHAR(10)
@@ -630,6 +634,7 @@ impl fmt::Display for DataType {
             DataType::Unspecified => Ok(()),
             DataType::Trigger => write!(f, "TRIGGER"),
             DataType::AnyType => write!(f, "ANY TYPE"),
+            DataType::Table(fields) => write!(f, "TABLE({})", display_comma_separated(fields)),
         }
     }
 }

src/parser/mod.rs

@@ -8867,6 +8867,10 @@ impl<'a> Parser<'a> {
                     let _ = self.parse_keyword(Keyword::TYPE);
                     Ok(DataType::AnyType)
                 }
+                Keyword::TABLE => {
+                    let columns = self.parse_returns_table_columns()?;
+                    Ok(DataType::Table(columns))
+                }
                 _ => {
                     self.prev_token();
                     let type_name = self.parse_object_name(false)?;
@@ -8894,6 +8898,24 @@ impl<'a> Parser<'a> {
         Ok((data, trailing_bracket))
     }
 
+    fn parse_returns_table_column(&mut self) -> Result<ColumnDef, ParserError> {
+        let name = self.parse_identifier()?;
+        let data_type = self.parse_data_type()?;
+        Ok(ColumnDef {
+            name,
+            data_type,
+            collation: None,
+            options: Vec::new(), // No constraints expected here
+        })
+    }
+
+    fn parse_returns_table_columns(&mut self) -> Result<Vec<ColumnDef>, ParserError> {
+        self.expect_token(&Token::LParen)?;
+        let columns = self.parse_comma_separated(Parser::parse_returns_table_column)?;
+        self.expect_token(&Token::RParen)?;
+        Ok(columns)
+    }
+
     pub fn parse_string_values(&mut self) -> Result<Vec<String>, ParserError> {
         self.expect_token(&Token::LParen)?;
         let mut values = Vec::new();

tests/sqlparser_postgres.rs

@@ -3803,6 +3803,7 @@ fn parse_create_function_detailed() {
     pg_and_generic().verified_stmt("CREATE OR REPLACE FUNCTION add(a INTEGER, IN b INTEGER = 1) RETURNS INTEGER LANGUAGE SQL STABLE CALLED ON NULL INPUT PARALLEL UNSAFE RETURN a + b");
     pg_and_generic().verified_stmt(r#"CREATE OR REPLACE FUNCTION increment(i INTEGER) RETURNS INTEGER LANGUAGE plpgsql AS $$ BEGIN RETURN i + 1; END; $$"#);
     pg_and_generic().verified_stmt(r#"CREATE OR REPLACE FUNCTION no_arg() RETURNS VOID LANGUAGE plpgsql AS $$ BEGIN DELETE FROM my_table; END; $$"#);
+    pg_and_generic().verified_stmt(r#"CREATE OR REPLACE FUNCTION return_table(i INTEGER) RETURNS TABLE(id UUID, is_active BOOLEAN) LANGUAGE plpgsql AS $$ BEGIN RETURN QUERY SELECT NULL::UUID, NULL::BOOLEAN; END; $$"#);
 }
 #[test]
 fn parse_incorrect_create_function_parallel() {