Use conditions but not repo ids as query condition (#16839)

* Use conditions but not repo ids as query condition

* Improve the performance of pulls/issue

* Remove duplicated code

* fix lint

* Fix bug

* Fix stats

* More fixes

* Fix build

* Fix lint

* Fix test

* Fix build

* Adjust the logic

* Merge

* Fix conflicts

* improve the performance

* Add comments for the query conditions functions

* Some improvements

models/repo/repo_list.go

@@ -0,0 +1,46 @@
+// 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 repo
+
+import (
+	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/modules/setting"
+)
+
+// GetUserMirrorRepositories returns a list of mirror repositories of given user.
+func GetUserMirrorRepositories(userID int64) ([]*Repository, error) {
+	repos := make([]*Repository, 0, 10)
+	return repos, db.GetEngine(db.DefaultContext).
+		Where("owner_id = ?", userID).
+		And("is_mirror = ?", true).
+		Find(&repos)
+}
+
+// IterateRepository iterate repositories
+func IterateRepository(f func(repo *Repository) error) error {
+	var start int
+	batchSize := setting.Database.IterateBufferSize
+	for {
+		repos := make([]*Repository, 0, batchSize)
+		if err := db.GetEngine(db.DefaultContext).Limit(batchSize, start).Find(&repos); err != nil {
+			return err
+		}
+		if len(repos) == 0 {
+			return nil
+		}
+		start += len(repos)
+
+		for _, repo := range repos {
+			if err := f(repo); err != nil {
+				return err
+			}
+		}
+	}
+}
+
+// FindReposMapByIDs find repos as map
+func FindReposMapByIDs(repoIDs []int64, res map[int64]*Repository) error {
+	return db.GetEngine(db.DefaultContext).In("id", repoIDs).Find(&res)
+}