dialect/sql/schema: handle index prefix key limit in older versions of mariadb

Fixed #1378

dialect/sql/schema/mysql.go

@@ -244,7 +244,7 @@ func (d *MySQL) cType(c *Column) (t string) {
 	case field.TypeString:
 		size := c.Size
 		if size == 0 {
-			size = c.defaultSize(d.version)
+			size = d.defaultSize(c)
 		}
 		if size <= math.MaxUint16 {
 			t = fmt.Sprintf("varchar(%d)", size)
@@ -659,3 +659,24 @@ func (d *MySQL) fkNames(ctx context.Context, tx dialect.Tx, table, column string
 	}
 	return names, nil
 }
+
+// defaultSize returns the default size for MySQL/MariaDB varchar type
+// based on column size, charset and table indexes, in order to avoid
+// index prefix key limit (767) for older versions of MySQL/MariaDB.
+func (d *MySQL) defaultSize(c *Column) int64 {
+	size := DefaultStringLen
+	version, checked := d.version, "5.7.0"
+	if v, ok := d.mariadb(); ok {
+		version, checked = v, "10.2.2"
+	}
+	switch {
+	// Version is >= 5.7 for MySQL, or >= 10.2.2 for MariaDB.
+	case compareVersions(version, checked) != -1:
+	// Column is non-unique, or not part of any index (reaching
+	// the error 1071).
+	case !c.Unique && len(c.indexes) == 0:
+	default:
+		size = 191
+	}
+	return size
+}

dialect/sql/schema/mysql_test.go

@@ -1143,6 +1143,40 @@ func TestMySQL_Create(t *testing.T) {
 				mock.ExpectCommit()
 			},
 		},
+		{
+			name: "mariadb/10.1.37/create table",
+			tables: []*Table{
+				{
+					Name: "users",
+					PrimaryKey: []*Column{
+						{Name: "id", Type: field.TypeInt, Increment: true},
+					},
+					Columns: []*Column{
+						{Name: "id", Type: field.TypeInt, Increment: true},
+						{Name: "age", Type: field.TypeInt},
+						{Name: "name", Type: field.TypeString, Unique: true},
+					},
+				},
+			},
+			options: []MigrateOption{WithGlobalUniqueID(true)},
+			before: func(mock mysqlMock) {
+				mock.start("10.1.48-MariaDB-1~bionic")
+				mock.tableExists("ent_types", false)
+				// create ent_types table.
+				mock.ExpectExec(escape("CREATE TABLE IF NOT EXISTS `ent_types`(`id` bigint unsigned AUTO_INCREMENT NOT NULL, `type` varchar(191) UNIQUE NOT NULL, PRIMARY KEY(`id`)) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin")).
+					WillReturnResult(sqlmock.NewResult(0, 1))
+				mock.tableExists("users", false)
+				mock.ExpectExec(escape("CREATE TABLE IF NOT EXISTS `users`(`id` bigint AUTO_INCREMENT NOT NULL, `age` bigint NOT NULL, `name` varchar(191) UNIQUE NOT NULL, PRIMARY KEY(`id`)) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin")).
+					WillReturnResult(sqlmock.NewResult(0, 1))
+				// set users id range.
+				mock.ExpectExec(escape("INSERT INTO `ent_types` (`type`) VALUES (?)")).
+					WithArgs("users").
+					WillReturnResult(sqlmock.NewResult(0, 1))
+				mock.ExpectExec(escape("ALTER TABLE `users` AUTO_INCREMENT = 0")).
+					WillReturnResult(sqlmock.NewResult(0, 1))
+				mock.ExpectCommit()
+			},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {

dialect/sql/schema/schema.go

@@ -318,22 +318,6 @@ func (c *Column) nullable(b *sql.ColumnBuilder) {
 	b.Attr(attr)
 }
 
-// defaultSize returns the default size for MySQL varchar type based
-// on column size, charset and table indexes, in order to avoid index
-// prefix key limit (767).
-func (c *Column) defaultSize(version string) int64 {
-	size := DefaultStringLen
-	switch {
-	// version is >= 5.7.
-	case compareVersions(version, "5.7.0") != -1:
-	// non-unique, or not part of any index (reaching the error 1071).
-	case !c.Unique && len(c.indexes) == 0:
-	default:
-		size = 191
-	}
-	return size
-}
-
 // scanTypeOr returns the scanning type or the given value.
 func (c *Column) scanTypeOr(t string) string {
 	if c.typ != "" {