Delete Labels & IssueLabels on Repo Delete too (#15039)

* Doctor: find IssueLabels without existing label

* on Repo Delete: delete labels & issue_labels too

* performance nits

* Add Migration: Delete orphaned IssueLabels

* Migration v174: use Sync2

* USE sess !!!

* better func name

* code format & comment

* RAW SQL

* Update models/migrations/v176.go

* next try?

6 files changed, 98 insertions, 8 deletions

diff --git a/models/consistency.go b/models/consistency.go
index bed94d9395..9d76d26bbb 100644
--- a/models/consistency.go
+++ b/models/consistency.go
@@ -224,6 +224,23 @@ func DeleteOrphanedLabels() error {
 	return nil
 }
 
+// CountOrphanedIssueLabels return count of IssueLabels witch have no label behind anymore
+func CountOrphanedIssueLabels() (int64, error) {
+	return x.Table("issue_label").
+		Join("LEFT", "label", "issue_label.label_id = label.id").
+		Where(builder.IsNull{"label.id"}).Count()
+}
+
+// DeleteOrphanedIssueLabels delete IssueLabels witch have no label behind anymore
+func DeleteOrphanedIssueLabels() error {
+	_, err := x.In("id", builder.Select("issue_label.id").From("issue_label").
+		Join("LEFT", "label", "issue_label.label_id = label.id").
+		Where(builder.IsNull{"label.id"})).
+		Delete(IssueLabel{})
+
+	return err
+}
+
 // CountOrphanedIssues count issues without a repo
 func CountOrphanedIssues() (int64, error) {
 	return x.Table("issue").
diff --git a/models/issue_label.go b/models/issue_label.go
index e377ebf4e7..4f082b8a6e 100644
--- a/models/issue_label.go
+++ b/models/issue_label.go
@@ -780,3 +780,15 @@ func DeleteIssueLabel(issue *Issue, label *Label, doer *User) (err error) {
 
 	return sess.Commit()
 }
+
+func deleteLabelsByRepoID(sess Engine, repoID int64) error {
+	deleteCond := builder.Select("id").From("label").Where(builder.Eq{"label.repo_id": repoID})
+
+	if _, err := sess.In("label_id", deleteCond).
+		Delete(&IssueLabel{}); err != nil {
+		return err
+	}
+
+	_, err := sess.Delete(&Label{RepoID: repoID})
+	return err
+}
diff --git a/models/migrations/migrations.go b/models/migrations/migrations.go
index 3427b5dec1..2c85ebdfd7 100644
--- a/models/migrations/migrations.go
+++ b/models/migrations/migrations.go
@@ -295,11 +295,13 @@ var migrations = []Migration{
 	// v173 -> v174
 	NewMigration("Add time_id column to Comment", addTimeIDCommentColumn),
 	// v174 -> v175
-	NewMigration("create repo transfer table", addRepoTransfer),
+	NewMigration("Create repo transfer table", addRepoTransfer),
 	// v175 -> v176
 	NewMigration("Fix Postgres ID Sequences broken by recreate-table", fixPostgresIDSequences),
 	// v176 -> v177
 	NewMigration("Remove invalid labels from comments", removeInvalidLabels),
+	// v177 -> v178
+	NewMigration("Delete orphaned IssueLabels", deleteOrphanedIssueLabels),
 }
 
 // GetCurrentDBVersion returns the current db version
diff --git a/models/migrations/v174.go b/models/migrations/v174.go
index ce337df2b3..5915d3626b 100644
--- a/models/migrations/v174.go
+++ b/models/migrations/v174.go
@@ -5,6 +5,8 @@
 package migrations
 
 import (
+	"fmt"
+
 	"xorm.io/xorm"
 )
 
@@ -19,5 +21,15 @@ func addRepoTransfer(x *xorm.Engine) error {
 		UpdatedUnix int64 `xorm:"INDEX NOT NULL updated"`
 	}
 
-	return x.Sync(new(RepoTransfer))
+	sess := x.NewSession()
+	defer sess.Close()
+	if err := sess.Begin(); err != nil {
+		return err
+	}
+
+	if err := sess.Sync2(new(RepoTransfer)); err != nil {
+		return fmt.Errorf("Sync2: %v", err)
+	}
+
+	return sess.Commit()
 }
diff --git a/models/migrations/v177.go b/models/migrations/v177.go
new file mode 100644
index 0000000000..2329a8dc48
--- /dev/null
+++ b/models/migrations/v177.go
@@ -0,0 +1,42 @@
+// Copyright 2021 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 (
+	"fmt"
+
+	"xorm.io/xorm"
+)
+
+func deleteOrphanedIssueLabels(x *xorm.Engine) error {
+	type IssueLabel struct {
+		ID      int64 `xorm:"pk autoincr"`
+		IssueID int64 `xorm:"UNIQUE(s)"`
+		LabelID int64 `xorm:"UNIQUE(s)"`
+	}
+
+	sess := x.NewSession()
+	defer sess.Close()
+	if err := sess.Begin(); err != nil {
+		return err
+	}
+
+	if err := sess.Sync2(new(IssueLabel)); err != nil {
+		return fmt.Errorf("Sync2: %v", err)
+	}
+
+	if _, err := sess.Exec(`DELETE FROM issue_label WHERE issue_label.id IN (
+		SELECT ill.id FROM (
+			SELECT il.id
+			FROM issue_label AS il
+				LEFT JOIN label ON il.label_id = label.id
+			WHERE
+				label.id IS NULL
+		) AS ill)`); err != nil {
+		return err
+	}
+
+	return sess.Commit()
+}
diff --git a/models/repo.go b/models/repo.go
index 15d6351251..329e63cc42 100644
--- a/models/repo.go
+++ b/models/repo.go
@@ -1447,11 +1447,11 @@ func DeleteRepository(doer *User, uid, repoID int64) error {
 		releaseAttachments = append(releaseAttachments, attachments[i].RelativePath())
 	}
 
-	if _, err = sess.Exec("UPDATE `user` SET num_stars=num_stars-1 WHERE id IN (SELECT `uid` FROM `star` WHERE repo_id = ?)", repo.ID); err != nil {
+	if _, err := sess.Exec("UPDATE `user` SET num_stars=num_stars-1 WHERE id IN (SELECT `uid` FROM `star` WHERE repo_id = ?)", repo.ID); err != nil {
 		return err
 	}
 
-	if err = deleteBeans(sess,
+	if err := deleteBeans(sess,
 		&Access{RepoID: repo.ID},
 		&Action{RepoID: repo.ID},
 		&Watch{RepoID: repoID},
@@ -1475,28 +1475,33 @@ func DeleteRepository(doer *User, uid, repoID int64) error {
 		return fmt.Errorf("deleteBeans: %v", err)
 	}
 
+	// Delete Labels and related objects
+	if err := deleteLabelsByRepoID(sess, repoID); err != nil {
+		return err
+	}
+
 	// Delete Issues and related objects
 	var attachmentPaths []string
 	if attachmentPaths, err = deleteIssuesByRepoID(sess, repoID); err != nil {
 		return err
 	}
 
-	if _, err = sess.Where("repo_id = ?", repoID).Delete(new(RepoUnit)); err != nil {
+	if _, err := sess.Where("repo_id = ?", repoID).Delete(new(RepoUnit)); err != nil {
 		return err
 	}
 
 	if repo.IsFork {
-		if _, err = sess.Exec("UPDATE `repository` SET num_forks=num_forks-1 WHERE id=?", repo.ForkID); err != nil {
+		if _, err := sess.Exec("UPDATE `repository` SET num_forks=num_forks-1 WHERE id=?", repo.ForkID); err != nil {
 			return fmt.Errorf("decrease fork count: %v", err)
 		}
 	}
 
-	if _, err = sess.Exec("UPDATE `user` SET num_repos=num_repos-1 WHERE id=?", uid); err != nil {
+	if _, err := sess.Exec("UPDATE `user` SET num_repos=num_repos-1 WHERE id=?", uid); err != nil {
 		return err
 	}
 
 	if len(repo.Topics) > 0 {
-		if err = removeTopicsFromRepo(sess, repo.ID); err != nil {
+		if err := removeTopicsFromRepo(sess, repo.ID); err != nil {
 			return err
 		}
 	}