Move issue pin to an standalone table for querying performance (#33452)

Noticed a SQL in gitea.com has a bigger load. It seems both `is_pull`
and `pin_order` are not indexed columns in the database.

```SQL
SELECT `id`, `repo_id`, `index`, `poster_id`, `original_author`, `original_author_id`, `name`, `content`, `content_version`, `milestone_id`, `priority`, `is_closed`, `is_pull`, `num_comments`, `ref`, `pin_order`, `deadline_unix`, `created_unix`, `updated_unix`, `closed_unix`, `is_locked`, `time_estimate` FROM `issue` WHERE (repo_id =?) AND (is_pull = 0) AND (pin_order > 0) ORDER BY pin_order
```

I came across a comment
#24406 (comment)
from @delvh , which presents a more reasonable approach. Based on this,
this PR will migrate all issue and pull request pin data from the
`issue` table to the `issue_pin` table. This change benefits larger
Gitea instances by improving scalability and performance.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

Author: lunny

models/fixtures/issue_pin.yml

@@ -0,0 +1,6 @@
+-
+  id: 1
+  repo_id: 2
+  issue_id: 4
+  is_pull: false
+  pin_order: 1

models/issues/issue.go

@@ -97,7 +97,7 @@ type Issue struct {
 	// TODO: RemoveIssueRef: see "repo/issue/branch_selector_field.tmpl"
 	Ref string
 
-	PinOrder int `xorm:"DEFAULT 0"`
+	PinOrder int `xorm:"-"` // 0 means not loaded, -1 means loaded but not pinned
 
 	DeadlineUnix timeutil.TimeStamp `xorm:"INDEX"`
 
@@ -291,6 +291,23 @@ func (issue *Issue) LoadMilestone(ctx context.Context) (err error) {
 	return nil
 }
 
+func (issue *Issue) LoadPinOrder(ctx context.Context) error {
+	if issue.PinOrder != 0 {
+		return nil
+	}
+	issuePin, err := GetIssuePin(ctx, issue)
+	if err != nil && !db.IsErrNotExist(err) {
+		return err
+	}
+
+	if issuePin != nil {
+		issue.PinOrder = issuePin.PinOrder
+	} else {
+		issue.PinOrder = -1
+	}
+	return nil
+}
+
 // LoadAttributes loads the attribute of this issue.
 func (issue *Issue) LoadAttributes(ctx context.Context) (err error) {
 	if err = issue.LoadRepo(ctx); err != nil {
@@ -330,6 +347,10 @@ func (issue *Issue) LoadAttributes(ctx context.Context) (err error) {
 		return err
 	}
 
+	if err = issue.LoadPinOrder(ctx); err != nil {
+		return err
+	}
+
 	if err = issue.Comments.LoadAttributes(ctx); err != nil {
 		return err
 	}
@@ -342,6 +363,14 @@ func (issue *Issue) LoadAttributes(ctx context.Context) (err error) {
 	return issue.loadReactions(ctx)
 }
 
+// IsPinned returns if a Issue is pinned
+func (issue *Issue) IsPinned() bool {
+	if issue.PinOrder == 0 {
+		setting.PanicInDevOrTesting("issue's pinorder has not been loaded")
+	}
+	return issue.PinOrder > 0
+}
+
 func (issue *Issue) ResetAttributesLoaded() {
 	issue.isLabelsLoaded = false
 	issue.isMilestoneLoaded = false
@@ -720,190 +749,6 @@ func (issue *Issue) HasOriginalAuthor() bool {
 	return issue.OriginalAuthor != "" && issue.OriginalAuthorID != 0
 }
 
-var ErrIssueMaxPinReached = util.NewInvalidArgumentErrorf("the max number of pinned issues has been readched")
-
-// IsPinned returns if a Issue is pinned
-func (issue *Issue) IsPinned() bool {
-	return issue.PinOrder != 0
-}
-
-// Pin pins a Issue
-func (issue *Issue) Pin(ctx context.Context, user *user_model.User) error {
-	// If the Issue is already pinned, we don't need to pin it twice
-	if issue.IsPinned() {
-		return nil
-	}
-
-	var maxPin int
-	_, err := db.GetEngine(ctx).SQL("SELECT MAX(pin_order) FROM issue WHERE repo_id = ? AND is_pull = ?", issue.RepoID, issue.IsPull).Get(&maxPin)
-	if err != nil {
-		return err
-	}
-
-	// Check if the maximum allowed Pins reached
-	if maxPin >= setting.Repository.Issue.MaxPinned {
-		return ErrIssueMaxPinReached
-	}
-
-	_, err = db.GetEngine(ctx).Table("issue").
-		Where("id = ?", issue.ID).
-		Update(map[string]any{
-			"pin_order": maxPin + 1,
-		})
-	if err != nil {
-		return err
-	}
-
-	// Add the pin event to the history
-	opts := &CreateCommentOptions{
-		Type:  CommentTypePin,
-		Doer:  user,
-		Repo:  issue.Repo,
-		Issue: issue,
-	}
-	if _, err = CreateComment(ctx, opts); err != nil {
-		return err
-	}
-
-	return nil
-}
-
-// UnpinIssue unpins a Issue
-func (issue *Issue) Unpin(ctx context.Context, user *user_model.User) error {
-	// If the Issue is not pinned, we don't need to unpin it
-	if !issue.IsPinned() {
-		return nil
-	}
-
-	// This sets the Pin for all Issues that come after the unpined Issue to the correct value
-	_, err := db.GetEngine(ctx).Exec("UPDATE issue SET pin_order = pin_order - 1 WHERE repo_id = ? AND is_pull = ? AND pin_order > ?", issue.RepoID, issue.IsPull, issue.PinOrder)
-	if err != nil {
-		return err
-	}
-
-	_, err = db.GetEngine(ctx).Table("issue").
-		Where("id = ?", issue.ID).
-		Update(map[string]any{
-			"pin_order": 0,
-		})
-	if err != nil {
-		return err
-	}
-
-	// Add the unpin event to the history
-	opts := &CreateCommentOptions{
-		Type:  CommentTypeUnpin,
-		Doer:  user,
-		Repo:  issue.Repo,
-		Issue: issue,
-	}
-	if _, err = CreateComment(ctx, opts); err != nil {
-		return err
-	}
-
-	return nil
-}
-
-// PinOrUnpin pins or unpins a Issue
-func (issue *Issue) PinOrUnpin(ctx context.Context, user *user_model.User) error {
-	if !issue.IsPinned() {
-		return issue.Pin(ctx, user)
-	}
-
-	return issue.Unpin(ctx, user)
-}
-
-// MovePin moves a Pinned Issue to a new Position
-func (issue *Issue) MovePin(ctx context.Context, newPosition int) error {
-	// If the Issue is not pinned, we can't move them
-	if !issue.IsPinned() {
-		return nil
-	}
-
-	if newPosition < 1 {
-		return fmt.Errorf("The Position can't be lower than 1")
-	}
-
-	dbctx, committer, err := db.TxContext(ctx)
-	if err != nil {
-		return err
-	}
-	defer committer.Close()
-
-	var maxPin int
-	_, err = db.GetEngine(dbctx).SQL("SELECT MAX(pin_order) FROM issue WHERE repo_id = ? AND is_pull = ?", issue.RepoID, issue.IsPull).Get(&maxPin)
-	if err != nil {
-		return err
-	}
-
-	// If the new Position bigger than the current Maximum, set it to the Maximum
-	if newPosition > maxPin+1 {
-		newPosition = maxPin + 1
-	}
-
-	// Lower the Position of all Pinned Issue that came after the current Position
-	_, err = db.GetEngine(dbctx).Exec("UPDATE issue SET pin_order = pin_order - 1 WHERE repo_id = ? AND is_pull = ? AND pin_order > ?", issue.RepoID, issue.IsPull, issue.PinOrder)
-	if err != nil {
-		return err
-	}
-
-	// Higher the Position of all Pinned Issues that comes after the new Position
-	_, err = db.GetEngine(dbctx).Exec("UPDATE issue SET pin_order = pin_order + 1 WHERE repo_id = ? AND is_pull = ? AND pin_order >= ?", issue.RepoID, issue.IsPull, newPosition)
-	if err != nil {
-		return err
-	}
-
-	_, err = db.GetEngine(dbctx).Table("issue").
-		Where("id = ?", issue.ID).
-		Update(map[string]any{
-			"pin_order": newPosition,
-		})
-	if err != nil {
-		return err
-	}
-
-	return committer.Commit()
-}
-
-// GetPinnedIssues returns the pinned Issues for the given Repo and type
-func GetPinnedIssues(ctx context.Context, repoID int64, isPull bool) (IssueList, error) {
-	issues := make(IssueList, 0)
-
-	err := db.GetEngine(ctx).
-		Table("issue").
-		Where("repo_id = ?", repoID).
-		And("is_pull = ?", isPull).
-		And("pin_order > 0").
-		OrderBy("pin_order").
-		Find(&issues)
-	if err != nil {
-		return nil, err
-	}
-
-	err = issues.LoadAttributes(ctx)
-	if err != nil {
-		return nil, err
-	}
-
-	return issues, nil
-}
-
-// IsNewPinAllowed returns if a new Issue or Pull request can be pinned
-func IsNewPinAllowed(ctx context.Context, repoID int64, isPull bool) (bool, error) {
-	var maxPin int
-	_, err := db.GetEngine(ctx).SQL("SELECT COUNT(pin_order) FROM issue WHERE repo_id = ? AND is_pull = ? AND pin_order > 0", repoID, isPull).Get(&maxPin)
-	if err != nil {
-		return false, err
-	}
-
-	return maxPin < setting.Repository.Issue.MaxPinned, nil
-}
-
-// IsErrIssueMaxPinReached returns if the error is, that the User can't pin more Issues
-func IsErrIssueMaxPinReached(err error) bool {
-	return err == ErrIssueMaxPinReached
-}
-
 // InsertIssues insert issues to database
 func InsertIssues(ctx context.Context, issues ...*Issue) error {
 	ctx, committer, err := db.TxContext(ctx)

models/issues/issue_list.go

@@ -506,6 +506,39 @@ func (issues IssueList) loadTotalTrackedTimes(ctx context.Context) (err error) {
 	return nil
 }
 
+func (issues IssueList) LoadPinOrder(ctx context.Context) error {
+	if len(issues) == 0 {
+		return nil
+	}
+
+	issueIDs := container.FilterSlice(issues, func(issue *Issue) (int64, bool) {
+		return issue.ID, issue.PinOrder == 0
+	})
+	if len(issueIDs) == 0 {
+		return nil
+	}
+	issuePins, err := GetIssuePinsByIssueIDs(ctx, issueIDs)
+	if err != nil {
+		return err
+	}
+
+	for _, issue := range issues {
+		if issue.PinOrder != 0 {
+			continue
+		}
+		for _, pin := range issuePins {
+			if pin.IssueID == issue.ID {
+				issue.PinOrder = pin.PinOrder
+				break
+			}
+		}
+		if issue.PinOrder == 0 {
+			issue.PinOrder = -1
+		}
+	}
+	return nil
+}
+
 // loadAttributes loads all attributes, expect for attachments and comments
 func (issues IssueList) LoadAttributes(ctx context.Context) error {
 	if _, err := issues.LoadRepositories(ctx); err != nil {