diff --git a/models/issues/issue.go b/models/issues/issue.go
index 856e9da9807..7679c222633 100644
--- a/models/issues/issue.go
+++ b/models/issues/issue.go
@@ -55,7 +55,7 @@ var ErrIssueAlreadyChanged = util.NewInvalidArgumentErrorf("the issue is already
 // Issue represents an issue or pull request of repository.
 type Issue struct {
 	ID                int64                  `xorm:"pk autoincr"`
-	RepoID            int64                  `xorm:"INDEX UNIQUE(repo_index)"`
+	RepoID            int64                  `xorm:"INDEX(repo_closed_pull) UNIQUE(repo_index)"`
 	Repo              *repo_model.Repository `xorm:"-"`
 	Index             int64                  `xorm:"UNIQUE(repo_index)"` // Index in one repository.
 	PosterID          int64                  `xorm:"INDEX"`
@@ -77,9 +77,9 @@ type Issue struct {
 	AssigneeID        int64            `xorm:"-"`
 	Assignee          *user_model.User `xorm:"-"`
 	isAssigneeLoaded  bool             `xorm:"-"`
-	IsClosed          bool             `xorm:"INDEX"`
+	IsClosed          bool             `xorm:"INDEX(repo_closed_pull)"`
 	IsRead            bool             `xorm:"-"`
-	IsPull            bool             `xorm:"INDEX"` // Indicates whether is a pull request or not.
+	IsPull            bool             `xorm:"INDEX(repo_closed_pull)"` // Indicates whether is a pull request or not.
 	PullRequest       *PullRequest     `xorm:"-"`
 	NumComments       int
 
diff --git a/models/issues/pull_list.go b/models/issues/pull_list.go
index cdd5cb54eeb..c7804e68be5 100644
--- a/models/issues/pull_list.go
+++ b/models/issues/pull_list.go
@@ -335,8 +335,8 @@ func (prs PullRequestList) LoadReviews(ctx context.Context) (ReviewList, error)
 			"reviewer_team_id":   0,
 		}).
 		GroupBy("issue_id, reviewer_id")
-	// Get latest review of each reviewer, sorted in order they were made
-	if err := db.GetEngine(ctx).In("id", subQuery).OrderBy("review.updated_unix ASC").Find(&reviews); err != nil {
+	// Get latest review of each reviewer, sorted in order they were made. Joined because MySQL scans all reviews for "id IN (subquery)", xorm aliases the subquery "review".
+	if err := db.GetEngine(ctx).Table("review").Alias("latest").Join("INNER", subQuery, "latest.id = review.id").OrderBy("latest.updated_unix ASC").Find(&reviews); err != nil {
 		return nil, err
 	}
 
@@ -350,7 +350,7 @@ func (prs PullRequestList) LoadReviews(ctx context.Context) (ReviewList, error)
 		"reviewer_team_id": 0,
 	}).
 		GroupBy("issue_id, reviewer_team_id")
-	if err := db.GetEngine(ctx).In("id", subQueryTeam).OrderBy("review.updated_unix ASC").Find(&teamReviewRequests); err != nil {
+	if err := db.GetEngine(ctx).Table("review").Alias("latest").Join("INNER", subQueryTeam, "latest.id = review.id").OrderBy("latest.updated_unix ASC").Find(&teamReviewRequests); err != nil {
 		return nil, err
 	}
 
diff --git a/models/organization/team_repo.go b/models/organization/team_repo.go
index f41f8fbb0d6..11dc06501bd 100644
--- a/models/organization/team_repo.go
+++ b/models/organization/team_repo.go
@@ -13,12 +13,12 @@ import (
 	"xorm.io/builder"
 )
 
-// TeamRepo represents an team-repository relation.
+// TeamRepo represents an org-team-repository relation.
 type TeamRepo struct {
 	ID     int64 `xorm:"pk autoincr"`
 	OrgID  int64 `xorm:"INDEX"`
 	TeamID int64 `xorm:"UNIQUE(s)"`
-	RepoID int64 `xorm:"UNIQUE(s)"`
+	RepoID int64 `xorm:"UNIQUE(s) INDEX"`
 }
 
 // HasTeamRepo returns true if given repository belongs to team.
diff --git a/models/perm/access/access.go b/models/perm/access/access.go
index 6b6698fe28e..ec78846ae33 100644
--- a/models/perm/access/access.go
+++ b/models/perm/access/access.go
@@ -25,7 +25,7 @@ import (
 type Access struct {
 	ID     int64 `xorm:"pk autoincr"`
 	UserID int64 `xorm:"UNIQUE(s)"`
-	RepoID int64 `xorm:"UNIQUE(s)"`
+	RepoID int64 `xorm:"UNIQUE(s) INDEX"`
 	Mode   perm.AccessMode
 }
 
diff --git a/models/repo/repo.go b/models/repo/repo.go
index 55d7d2ed814..bafc9b5d025 100644
--- a/models/repo/repo.go
+++ b/models/repo/repo.go
@@ -494,10 +494,9 @@ func (repo *Repository) composeCommonMetas(ctx context.Context) map[string]strin
 		repo.MustOwner(ctx)
 		if repo.Owner.IsOrganization() {
 			teams := make([]string, 0, 5)
-			_ = db.GetEngine(ctx).Table("team_repo").
+			_ = db.GetEngine(ctx).Select("team.lower_name").Table("team_repo").
 				Join("INNER", "team", "team.id = team_repo.team_id").
 				Where("team_repo.repo_id = ?", repo.ID).
-				Select("team.lower_name").
 				OrderBy("team.lower_name").
 				Find(&teams)
 			metas["teams"] = "," + strings.Join(teams, ",") + ","
diff --git a/services/issue/issue.go b/services/issue/issue.go
index 50e373341a5..b537eaee4e2 100644
--- a/services/issue/issue.go
+++ b/services/issue/issue.go
@@ -290,7 +290,6 @@ func DeleteIssuesByRepoID(ctx context.Context, repoID int64) (attachmentPaths []
 		issues := make([]*issues_model.Issue, 0, db.DefaultMaxInSize)
 		if err := db.GetEngine(ctx).
 			Where("repo_id = ?", repoID).
-			OrderBy("id").
 			Limit(db.DefaultMaxInSize).
 			Find(&issues); err != nil {
 			return nil, err