Update topics repo count when deleting repository (#10051)

* Update topics repo count when deleting repository

* Add migration to fix incorrect data

* Optimize to use single update to recalculate values

models/migrations/migrations.go

@@ -306,6 +306,8 @@ var migrations = []Migration{
 	NewMigration("Add columns to user and repository", addUserRepoMissingColumns),
 	// v125 -> v126
 	NewMigration("Add some columns on review for migration", addReviewMigrateInfo),
+	// v126 -> v127
+	NewMigration("Fix topic repository count", fixTopicRepositoryCount),
 }
 
 // Migrate database to current version

models/migrations/v126.go

@@ -0,0 +1,25 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package migrations
+
+import (
+	"xorm.io/builder"
+	"xorm.io/xorm"
+)
+
+func fixTopicRepositoryCount(x *xorm.Engine) error {
+	_, err := x.Exec(builder.Delete(builder.NotIn("`repo_id`", builder.Select("`id`").From("`repository`"))).From("`repo_topic`"))
+	if err != nil {
+		return err
+	}
+
+	_, err = x.Exec(builder.Update(
+		builder.Eq{
+			"`repo_count`": builder.Select("count(*)").From("`repo_topic`").Where(builder.Eq{
+				"`repo_topic`.`topic_id`": builder.Expr("`topic`.`id`"),
+			}),
+		}).From("`topic`").Where(builder.Eq{"'1'": "1"}))
+	return err
+}