Support ALTER TABLE DROP PRIMARY KEY (#682)

* parse alter table drop primary key

* cargo nightly fmt

* add Dialect validation

src/ast/ddl.rs

@@ -44,6 +44,10 @@ pub enum AlterTableOperation {
         if_exists: bool,
         cascade: bool,
     },
+    /// `DROP PRIMARY KEY`
+    ///
+    /// Note: this is a MySQL-specific operation.
+    DropPrimaryKey,
     /// `RENAME TO PARTITION (partition=val)`
     RenamePartitions {
         old_partitions: Vec<Expr>,
@@ -124,6 +128,7 @@ impl fmt::Display for AlterTableOperation {
                     if *cascade { " CASCADE" } else { "" },
                 )
             }
+            AlterTableOperation::DropPrimaryKey => write!(f, "DROP PRIMARY KEY"),
             AlterTableOperation::DropColumn {
                 column_name,
                 if_exists,

src/parser.rs

@@ -3137,6 +3137,10 @@ impl<'a> Parser<'a> {
                     name,
                     cascade,
                 }
+            } else if self.parse_keywords(&[Keyword::PRIMARY, Keyword::KEY])
+                && dialect_of!(self is MySqlDialect | GenericDialect)
+            {
+                AlterTableOperation::DropPrimaryKey
             } else {
                 let _ = self.parse_keyword(Keyword::COLUMN);
                 let if_exists = self.parse_keywords(&[Keyword::IF, Keyword::EXISTS]);

tests/sqlparser_mysql.rs

@@ -875,6 +875,19 @@ fn parse_update_with_joins() {
     }
 }
 
+#[test]
+fn parse_alter_table_drop_primary_key() {
+    match mysql_and_generic().verified_stmt("ALTER TABLE tab DROP PRIMARY KEY") {
+        Statement::AlterTable {
+            name,
+            operation: AlterTableOperation::DropPrimaryKey,
+        } => {
+            assert_eq!("tab", name.to_string());
+        }
+        _ => unreachable!(),
+    }
+}
+
 #[test]
 fn parse_alter_table_change_column() {
     let expected_name = ObjectName(vec![Ident::new("orders")]);