Recreate Tables should Recreate indexes on MySQL (#16718) (#16740)

Backport #16718

The MySQL indexes are not being renamed at the same time as RENAME table despite the
CASCADE. Therefore it is probably better to just recreate the indexes instead.

Signed-off-by: Andrew Thornton <art27@cantab.net>

models/migrations/migrations.go

@@ -565,11 +565,26 @@ func recreateTable(sess *xorm.Session, bean interface{}) error {
 			return err
 		}
 
+		if err := sess.Table(tempTableName).DropIndexes(bean); err != nil {
+			log.Error("Unable to drop indexes on temporary table %s. Error: %v", tempTableName, err)
+			return err
+		}
+
 		// SQLite and MySQL will move all the constraints from the temporary table to the new table
 		if _, err := sess.Exec(fmt.Sprintf("ALTER TABLE `%s` RENAME TO `%s`", tempTableName, tableName)); err != nil {
 			log.Error("Unable to rename %s to %s. Error: %v", tempTableName, tableName, err)
 			return err
 		}
+
+		if err := sess.Table(tableName).CreateIndexes(bean); err != nil {
+			log.Error("Unable to recreate indexes on table %s. Error: %v", tableName, err)
+			return err
+		}
+
+		if err := sess.Table(tableName).CreateUniques(bean); err != nil {
+			log.Error("Unable to recreate uniques on table %s. Error: %v", tableName, err)
+			return err
+		}
 	case setting.Database.UsePostgreSQL:
 		var originalSequences []string
 		type sequenceData struct {