Code review comments

src/ast/ddl.rs

@@ -893,7 +893,7 @@ pub enum AlterColumnOperation {
         data_type: DataType,
         /// PostgreSQL specific
         using: Option<Expr>,
-        /// Whether the statement included the optional `SET DATA` keywords
+        /// Set to true if the statement includes the `SET DATA TYPE` keywords
         had_set: bool,
     },
 

src/dialect/mod.rs

@@ -1061,18 +1061,11 @@ pub trait Dialect: Debug + Any {
         false
     }
 
-    /// Returns true if the dialect supports `ALTER TABLE tbl ALTER COLUMN col TYPE <type>`
-    /// without specifying `SET DATA` before `TYPE`.
-    ///
-    /// - [Redshift](https://docs.aws.amazon.com/redshift/latest/dg/r_ALTER_TABLE.html#r_ALTER_TABLE-synopsis)
-    /// - [PostgreSQL](https://www.postgresql.org/docs/current/sql-altertable.html)
-    fn supports_alter_column_type_without_set(&self) -> bool {
-        false
-    }
-
-    /// Returns true if the dialect supports `ALTER TABLE tbl ALTER COLUMN col SET DATA TYPE <type> USING <exp>`
-    ///
-    /// - [PostgreSQL](https://www.postgresql.org/docs/current/sql-altertable.html)
+    /// Returns true if the dialect supports the `USING` clause in an `ALTER COLUMN` statement.
+    /// Example:
+    ///  ```sql
+    ///  ALTER TABLE tbl ALTER COLUMN col SET DATA TYPE <type> USING <exp>`
+    /// ```
     fn supports_alter_column_type_using(&self) -> bool {
         false
     }

src/dialect/postgresql.rs

@@ -259,10 +259,6 @@ impl Dialect for PostgreSqlDialect {
         true
     }
 
-    fn supports_alter_column_type_without_set(&self) -> bool {
-        true
-    }
-
     fn supports_alter_column_type_using(&self) -> bool {
         true
     }

src/dialect/redshift.rs

@@ -129,8 +129,4 @@ impl Dialect for RedshiftSqlDialect {
     fn supports_string_literal_backslash_escape(&self) -> bool {
         true
     }
-
-    fn supports_alter_column_type_without_set(&self) -> bool {
-        true
-    }
 }

src/parser/mod.rs

@@ -8736,9 +8736,7 @@ impl<'a> Parser<'a> {
                 AlterColumnOperation::DropDefault {}
             } else if self.parse_keywords(&[Keyword::SET, Keyword::DATA, Keyword::TYPE]) {
                 self.parse_set_data_type(true)?
-            } else if self.dialect.supports_alter_column_type_without_set()
-                && self.parse_keyword(Keyword::TYPE)
-            {
+            } else if self.parse_keyword(Keyword::TYPE) {
                 self.parse_set_data_type(false)?
             } else if self.parse_keywords(&[Keyword::ADD, Keyword::GENERATED]) {
                 let generated_as = if self.parse_keyword(Keyword::ALWAYS) {

tests/sqlparser_common.rs

@@ -5063,17 +5063,7 @@ fn parse_alter_table_alter_column_type() {
         }
         _ => unreachable!(),
     }
-
-    let dialects = all_dialects_where(|d| d.supports_alter_column_type_without_set());
-    dialects.verified_stmt(&format!("{alter_stmt} ALTER COLUMN is_active TYPE TEXT"));
-
-    let dialects = all_dialects_except(|d| d.supports_alter_column_type_without_set());
-    let res =
-        dialects.parse_sql_statements(&format!("{alter_stmt} ALTER COLUMN is_active TYPE TEXT"));
-    assert_eq!(
-        ParserError::ParserError("Expected: SET/DROP NOT NULL, SET DEFAULT, or SET DATA TYPE after ALTER COLUMN, found: TYPE".to_string()),
-        res.unwrap_err()
-    );
+    verified_stmt(&format!("{alter_stmt} ALTER COLUMN is_active TYPE TEXT"));
 
     let dialects = all_dialects_where(|d| d.supports_alter_column_type_using());
     dialects.verified_stmt(&format!(