Fix drift with missing sort order.

Sometimes the database gives us nothing, and sometimes `ASC` depending on its
mood when sort order is not defined. We should compare `None` to be the same as
`Some(Asc)` in these cases.

libs/sql-schema-describer/src/lib.rs

@@ -269,6 +269,12 @@ pub enum SQLSortOrder {
     Desc,
 }
 
+impl Default for SQLSortOrder {
+    fn default() -> Self {
+        Self::Asc
+    }
+}
+
 impl AsRef<str> for SQLSortOrder {
     fn as_ref(&self) -> &str {
         match self {

migration-engine/connectors/sql-migration-connector/src/sql_schema_differ/table.rs

@@ -168,7 +168,7 @@ fn indexes_match(first: &IndexWalker<'_>, second: &IndexWalker<'_>) -> bool {
         && left_cols.zip(right_cols).all(|(a, b)| {
             let names_match = a.as_column().name() == b.as_column().name();
             let lengths_match = a.length() == b.length();
-            let orders_match = a.sort_order() == b.sort_order();
+            let orders_match = a.sort_order().unwrap_or_default() == b.sort_order().unwrap_or_default();
 
             names_match && lengths_match && orders_match
         })

migration-engine/migration-engine-tests/tests/schema_push/mod.rs

@@ -1,3 +1,4 @@
+use indoc::indoc;
 use migration_engine_tests::test_api::*;
 use sql_schema_describer::ColumnTypeFamily;
 
@@ -393,3 +394,29 @@ fn implicit_relations_indices_are_not_renamed_unnecessarily(api: TestApi) {
         .send_sync()
         .assert_migration_directories_count(1);
 }
+
+#[test_connector(tags(Mysql), preview_features("extendedIndexes"))]
+fn mysql_should_diff_column_ordering_correctly_issue_10983(api: TestApi) {
+    // https://github.com/prisma/prisma/issues/10983
+
+    let dm = indoc! {r#"
+        model a {
+          id Int       @id @default(autoincrement())
+          b  DateTime? @db.DateTime(6)
+
+          @@index([b], map: "IDX_b")
+        }
+    "#};
+
+    let ddl = r#"
+        CREATE TABLE `a` (
+          `id` int(11) NOT NULL AUTO_INCREMENT,
+          `b` datetime(6) DEFAULT NULL,
+          PRIMARY KEY (`id`),
+          KEY `IDX_b` (`b`)
+        )
+    "#;
+
+    api.raw_cmd(ddl);
+    api.schema_push_w_datasource(dm).send().assert_green().assert_no_steps();
+}