Fix commit status index problem (#17061)

* Fix commit status index problem

* remove unused functions

* Add fixture and test for migration

* Fix lint

* Fix fixture

* Fix lint

* Fix test

* Fix bug

* Fix bug

7 files changed, 211 insertions, 19 deletions

diff --git a/models/commit_status.go b/models/commit_status.go
index f3639e819e..7ec233e80d 100644
--- a/models/commit_status.go
+++ b/models/commit_status.go
@@ -40,6 +40,82 @@ type CommitStatus struct {
 
 func init() {
 	db.RegisterModel(new(CommitStatus))
+	db.RegisterModel(new(CommitStatusIndex))
+}
+
+// upsertCommitStatusIndex the function will not return until it acquires the lock or receives an error.
+func upsertCommitStatusIndex(e db.Engine, repoID int64, sha string) (err error) {
+	// An atomic UPSERT operation (INSERT/UPDATE) is the only operation
+	// that ensures that the key is actually locked.
+	switch {
+	case setting.Database.UseSQLite3 || setting.Database.UsePostgreSQL:
+		_, err = e.Exec("INSERT INTO `commit_status_index` (repo_id, sha, max_index) "+
+			"VALUES (?,?,1) ON CONFLICT (repo_id,sha) DO UPDATE SET max_index = `commit_status_index`.max_index+1",
+			repoID, sha)
+	case setting.Database.UseMySQL:
+		_, err = e.Exec("INSERT INTO `commit_status_index` (repo_id, sha, max_index) "+
+			"VALUES (?,?,1) ON DUPLICATE KEY UPDATE max_index = max_index+1",
+			repoID, sha)
+	case setting.Database.UseMSSQL:
+		// https://weblogs.sqlteam.com/dang/2009/01/31/upsert-race-condition-with-merge/
+		_, err = e.Exec("MERGE `commit_status_index` WITH (HOLDLOCK) as target "+
+			"USING (SELECT ? AS repo_id, ? AS sha) AS src "+
+			"ON src.repo_id = target.repo_id AND src.sha = target.sha "+
+			"WHEN MATCHED THEN UPDATE SET target.max_index = target.max_index+1 "+
+			"WHEN NOT MATCHED THEN INSERT (repo_id, sha, max_index) "+
+			"VALUES (src.repo_id, src.sha, 1);",
+			repoID, sha)
+	default:
+		return fmt.Errorf("database type not supported")
+	}
+	return
+}
+
+// GetNextCommitStatusIndex retried 3 times to generate a resource index
+func GetNextCommitStatusIndex(repoID int64, sha string) (int64, error) {
+	for i := 0; i < db.MaxDupIndexAttempts; i++ {
+		idx, err := getNextCommitStatusIndex(repoID, sha)
+		if err == db.ErrResouceOutdated {
+			continue
+		}
+		if err != nil {
+			return 0, err
+		}
+		return idx, nil
+	}
+	return 0, db.ErrGetResourceIndexFailed
+}
+
+// getNextCommitStatusIndex return the next index
+func getNextCommitStatusIndex(repoID int64, sha string) (int64, error) {
+	ctx, commiter, err := db.TxContext()
+	if err != nil {
+		return 0, err
+	}
+	defer commiter.Close()
+
+	var preIdx int64
+	_, err = ctx.Engine().SQL("SELECT max_index FROM `commit_status_index` WHERE repo_id = ? AND sha = ?", repoID, sha).Get(&preIdx)
+	if err != nil {
+		return 0, err
+	}
+
+	if err := upsertCommitStatusIndex(ctx.Engine(), repoID, sha); err != nil {
+		return 0, err
+	}
+
+	var curIdx int64
+	has, err := ctx.Engine().SQL("SELECT max_index FROM `commit_status_index` WHERE repo_id = ? AND sha = ? AND max_index=?", repoID, sha, preIdx+1).Get(&curIdx)
+	if err != nil {
+		return 0, err
+	}
+	if !has {
+		return 0, db.ErrResouceOutdated
+	}
+	if err := commiter.Commit(); err != nil {
+		return 0, err
+	}
+	return curIdx, nil
 }
 
 func (status *CommitStatus) loadAttributes(e db.Engine) (err error) {
@@ -142,6 +218,14 @@ func sortCommitStatusesSession(sess *xorm.Session, sortType string) {
 	}
 }
 
+// CommitStatusIndex represents a table for commit status index
+type CommitStatusIndex struct {
+	ID       int64
+	RepoID   int64  `xorm:"unique(repo_sha)"`
+	SHA      string `xorm:"unique(repo_sha)"`
+	MaxIndex int64  `xorm:"index"`
+}
+
 // GetLatestCommitStatus returns all statuses with a unique context for a given commit.
 func GetLatestCommitStatus(repoID int64, sha string, listOptions ListOptions) ([]*CommitStatus, error) {
 	return getLatestCommitStatus(db.DefaultContext().Engine(), repoID, sha, listOptions)
@@ -206,6 +290,12 @@ func NewCommitStatus(opts NewCommitStatusOptions) error {
 		return fmt.Errorf("NewCommitStatus[%s, %s]: no user specified", repoPath, opts.SHA)
 	}
 
+	// Get the next Status Index
+	idx, err := GetNextCommitStatusIndex(opts.Repo.ID, opts.SHA)
+	if err != nil {
+		return fmt.Errorf("generate commit status index failed: %v", err)
+	}
+
 	ctx, committer, err := db.TxContext()
 	if err != nil {
 		return fmt.Errorf("NewCommitStatus[repo_id: %d, user_id: %d, sha: %s]: %v", opts.Repo.ID, opts.Creator.ID, opts.SHA, err)
@@ -218,22 +308,7 @@ func NewCommitStatus(opts NewCommitStatusOptions) error {
 	opts.CommitStatus.SHA = opts.SHA
 	opts.CommitStatus.CreatorID = opts.Creator.ID
 	opts.CommitStatus.RepoID = opts.Repo.ID
-
-	// Get the next Status Index
-	var nextIndex int64
-	lastCommitStatus := &CommitStatus{
-		SHA:    opts.SHA,
-		RepoID: opts.Repo.ID,
-	}
-	has, err := ctx.Engine().Desc("index").Limit(1).Get(lastCommitStatus)
-	if err != nil {
-		return fmt.Errorf("NewCommitStatus[%s, %s]: %v", repoPath, opts.SHA, err)
-	}
-	if has {
-		log.Debug("NewCommitStatus[%s, %s]: found", repoPath, opts.SHA)
-		nextIndex = lastCommitStatus.Index
-	}
-	opts.CommitStatus.Index = nextIndex + 1
+	opts.CommitStatus.Index = idx
 	log.Debug("NewCommitStatus[%s, %s]: %d", repoPath, opts.SHA, opts.CommitStatus.Index)
 
 	opts.CommitStatus.ContextHash = hashCommitStatusContext(opts.CommitStatus.Context)
diff --git a/models/db/index.go b/models/db/index.go
index 873289db54..0086a8f548 100644
--- a/models/db/index.go
+++ b/models/db/index.go
@@ -54,12 +54,13 @@ var (
 )
 
 const (
-	maxDupIndexAttempts = 3
+	// MaxDupIndexAttempts max retry times to create index
+	MaxDupIndexAttempts = 3
 )
 
 // GetNextResourceIndex retried 3 times to generate a resource index
 func GetNextResourceIndex(tableName string, groupID int64) (int64, error) {
-	for i := 0; i < maxDupIndexAttempts; i++ {
+	for i := 0; i < MaxDupIndexAttempts; i++ {
 		idx, err := getNextResourceIndex(tableName, groupID)
 		if err == ErrResouceOutdated {
 			continue
diff --git a/models/fixtures/commit_status_index.yml b/models/fixtures/commit_status_index.yml
new file mode 100644
index 0000000000..3f252e87ef
--- /dev/null
+++ b/models/fixtures/commit_status_index.yml
@@ -0,0 +1,5 @@
+-
+  id: 1
+  repo_id: 1
+  sha: "1234123412341234123412341234123412341234"
+  max_index: 5
\ No newline at end of file
diff --git a/models/migrations/migrations.go b/models/migrations/migrations.go
index fb6958f2da..3f90e5e74a 100644
--- a/models/migrations/migrations.go
+++ b/models/migrations/migrations.go
@@ -342,6 +342,8 @@ var migrations = []Migration{
 	NewMigration("Add repo id column for attachment table", addRepoIDForAttachment),
 	// v194 -> v195
 	NewMigration("Add Branch Protection Unprotected Files Column", addBranchProtectionUnprotectedFilesColumn),
+	// v196 -> v197
+	NewMigration("Add table commit_status_index", addTableCommitStatusIndex),
 }
 
 // GetCurrentDBVersion returns the current db version
diff --git a/models/migrations/v195.go b/models/migrations/v195.go
new file mode 100644
index 0000000000..06694eb57d
--- /dev/null
+++ b/models/migrations/v195.go
@@ -0,0 +1,47 @@
+// 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 addTableCommitStatusIndex(x *xorm.Engine) error {
+	// CommitStatusIndex represents a table for commit status index
+	type CommitStatusIndex struct {
+		ID       int64
+		RepoID   int64  `xorm:"unique(repo_sha)"`
+		SHA      string `xorm:"unique(repo_sha)"`
+		MaxIndex int64  `xorm:"index"`
+	}
+
+	if err := x.Sync2(new(CommitStatusIndex)); err != nil {
+		return fmt.Errorf("Sync2: %v", err)
+	}
+
+	sess := x.NewSession()
+	defer sess.Close()
+
+	if err := sess.Begin(); err != nil {
+		return err
+	}
+
+	// Remove data we're goint to rebuild
+	if _, err := sess.Table("commit_status_index").Where("1=1").Delete(&CommitStatusIndex{}); err != nil {
+		return err
+	}
+
+	// Create current data for all repositories with issues and PRs
+	if _, err := sess.Exec("INSERT INTO commit_status_index (repo_id, sha, max_index) " +
+		"SELECT max_data.repo_id, max_data.sha, max_data.max_index " +
+		"FROM ( SELECT commit_status.repo_id AS repo_id, commit_status.sha AS sha, max(commit_status.`index`) AS max_index " +
+		"FROM commit_status GROUP BY commit_status.repo_id, commit_status.sha) AS max_data"); err != nil {
+		return err
+	}
+
+	return sess.Commit()
+}
diff --git a/models/migrations/v195_test.go b/models/migrations/v195_test.go
new file mode 100644
index 0000000000..baf9cb61c2
--- /dev/null
+++ b/models/migrations/v195_test.go
@@ -0,0 +1,62 @@
+// 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 (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_addTableCommitStatusIndex(t *testing.T) {
+	// Create the models used in the migration
+	type CommitStatus struct {
+		ID     int64  `xorm:"pk autoincr"`
+		Index  int64  `xorm:"INDEX UNIQUE(repo_sha_index)"`
+		RepoID int64  `xorm:"INDEX UNIQUE(repo_sha_index)"`
+		SHA    string `xorm:"VARCHAR(64) NOT NULL INDEX UNIQUE(repo_sha_index)"`
+	}
+
+	// Prepare and load the testing database
+	x, deferable := prepareTestEnv(t, 0, new(CommitStatus))
+	if x == nil || t.Failed() {
+		defer deferable()
+		return
+	}
+	defer deferable()
+
+	// Run the migration
+	if err := addTableCommitStatusIndex(x); err != nil {
+		assert.NoError(t, err)
+		return
+	}
+
+	type CommitStatusIndex struct {
+		ID       int64
+		RepoID   int64  `xorm:"unique(repo_sha)"`
+		SHA      string `xorm:"unique(repo_sha)"`
+		MaxIndex int64  `xorm:"index"`
+	}
+
+	var start = 0
+	const batchSize = 1000
+	for {
+		var indexes = make([]CommitStatusIndex, 0, batchSize)
+		err := x.Table("commit_status_index").Limit(batchSize, start).Find(&indexes)
+		assert.NoError(t, err)
+
+		for _, idx := range indexes {
+			var maxIndex int
+			has, err := x.SQL("SELECT max(`index`) FROM commit_status WHERE repo_id = ? AND sha = ?", idx.RepoID, idx.SHA).Get(&maxIndex)
+			assert.NoError(t, err)
+			assert.True(t, has)
+			assert.EqualValues(t, maxIndex, idx.MaxIndex)
+		}
+		if len(indexes) < batchSize {
+			break
+		}
+		start += len(indexes)
+	}
+}
diff --git a/models/pull.go b/models/pull.go
index 9251673576..5cb7b57286 100644
--- a/models/pull.go
+++ b/models/pull.go
@@ -450,7 +450,7 @@ func (pr *PullRequest) SetMerged() (bool, error) {
 func NewPullRequest(repo *Repository, issue *Issue, labelIDs []int64, uuids []string, pr *PullRequest) (err error) {
 	idx, err := db.GetNextResourceIndex("issue_index", repo.ID)
 	if err != nil {
-		return fmt.Errorf("generate issue index failed: %v", err)
+		return fmt.Errorf("generate pull request index failed: %v", err)
 	}
 
 	issue.Index = idx