Add Index to pull_auto_merge.doer_id (go-gitea#27811)

Reported at https://codeberg.org/forgejo/forgejo/issues/1677

This column is used by
[deleteUser](https://github.com/go-gitea/gitea/blob/f089be91da44ee3e85fbe326a204c7c8a5df3d31/services/user/delete.go#L90).

Note: This PR contains a Migration, so we can't backport it to 1.21.

models/migrations/migrations.go

@@ -548,6 +548,8 @@ var migrations = []Migration{
 	NewMigration("Rename user themes", v1_22.RenameUserThemes),
 	// v281 -> v282
 	NewMigration("Add auth_token table", v1_22.CreateAuthTokenTable),
+	// v282 -> v283
+	NewMigration("Add Index to pull_auto_merge.doer_id", v1_22.AddIndexToPullAutoMergeDoerID),
 }
 
 // GetCurrentDBVersion returns the current db version

models/migrations/v1_22/v282.go

@@ -0,0 +1,16 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_22 //nolint
+
+import (
+	"xorm.io/xorm"
+)
+
+func AddIndexToPullAutoMergeDoerID(x *xorm.Engine) error {
+	type PullAutoMerge struct {
+		DoerID int64 `xorm:"INDEX NOT NULL"`
+	}
+
+	return x.Sync(&PullAutoMerge{})
+}

models/pull/automerge.go

@@ -17,7 +17,7 @@ import (
 type AutoMerge struct {
 	ID          int64                 `xorm:"pk autoincr"`
 	PullID      int64                 `xorm:"UNIQUE"`
-	DoerID      int64                 `xorm:"NOT NULL"`
+	DoerID      int64                 `xorm:"INDEX NOT NULL"`
 	Doer        *user_model.User      `xorm:"-"`
 	MergeStyle  repo_model.MergeStyle `xorm:"varchar(30)"`
 	Message     string                `xorm:"LONGTEXT"`