remove stale watches

models/migrations/migrations.go

@@ -186,6 +186,8 @@ var migrations = []Migration{
 	NewMigration("add u2f", addU2FReg),
 	// v66 -> v67
 	NewMigration("add login source id column for public_key table", addLoginSourceIDToPublicKeyTable),
+	// v67 -> v68
+	NewMigration("remove stale watches", removeStaleWatches),
 }
 
 // Migrate database to current version

models/migrations/v67.go

@@ -0,0 +1,93 @@
+// Copyright 2018 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 (
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/go-xorm/xorm"
+)
+
+func removeStaleWatches(x *xorm.Engine) error {
+	type Watch struct {
+		ID     int64
+		UserID int64
+		RepoID int64
+	}
+
+	type Repository struct {
+		ID        int64
+		IsPrivate bool
+		OwnerID   int64
+	}
+
+	type Access struct {
+		UserID int64
+		RepoID int64
+		Mode   int
+	}
+
+	const (
+		// AccessModeNone no access
+		AccessModeNone int = iota // 0
+		// AccessModeRead read access
+		AccessModeRead // 1
+	)
+
+	accessLevel := func(userID int64, repo *Repository) (int, error) {
+		mode := AccessModeNone
+		if !repo.IsPrivate {
+			mode = AccessModeRead
+		}
+
+		if userID == 0 {
+			return mode, nil
+		}
+
+		if userID == repo.OwnerID {
+			return 4, nil
+		}
+
+		a := &Access{UserID: userID, RepoID: repo.ID}
+		if has, err := x.Get(a); !has || err != nil {
+			return mode, err
+		}
+		return a.Mode, nil
+	}
+
+	repoCache := make(map[int64]*Repository)
+	return x.BufferSize(setting.IterateBufferSize).Iterate(new(Watch),
+		func(idx int, bean interface{}) error {
+			watch := bean.(*Watch)
+
+			repo := repoCache[watch.RepoID]
+			if repo == nil {
+				repo = &Repository{
+					ID: watch.RepoID,
+				}
+				if _, err := x.Get(repo); err != nil {
+					return err
+				}
+			}
+
+			// Remove watches from now unaccessible
+			mode, err := accessLevel(watch.UserID, repo)
+			if err != nil {
+				return err
+			}
+			has := AccessModeRead <= mode
+			if has {
+				return nil
+			}
+
+			sess := x.NewSession()
+			if _, err = sess.Delete(&Watch{0, watch.UserID, repo.ID}); err != nil {
+				return err
+			}
+			_, err = sess.Exec("UPDATE `repository` SET num_watches = num_watches - 1 WHERE id = ?", repo.ID)
+
+			return sess.Commit()
+		})
+}