Include OriginalAuthor in Reaction constraint (#13505)

When migrating repositories with reactions with deleted users, the original
author id may be -1. This means that it is possible to end up attempting
to create multiple reactions with the same [ Type, IssueID, CommentID, UserID,
OriginalAuthorID ] thus breaking the constraints.

On SQLite this appears to cause a deadlock but on other dbs this will
cause the migration to fail.

This PR extends the constraint to include the original author username
in the constraint.

Fix #13271

Signed-off-by: Andrew Thornton <art27@cantab.net>

models/issue_reaction.go

@@ -23,7 +23,7 @@ type Reaction struct {
 	CommentID        int64              `xorm:"INDEX UNIQUE(s)"`
 	UserID           int64              `xorm:"INDEX UNIQUE(s) NOT NULL"`
 	OriginalAuthorID int64              `xorm:"INDEX UNIQUE(s) NOT NULL DEFAULT(0)"`
-	OriginalAuthor   string
+	OriginalAuthor   string             `xorm:"INDEX UNIQUE(s)"`
 	User             *User              `xorm:"-"`
 	CreatedUnix      timeutil.TimeStamp `xorm:"INDEX created"`
 }

models/migrations/migrations.go

@@ -252,6 +252,8 @@ var migrations = []Migration{
 	NewMigration("ensure repo topics are up-to-date", fixRepoTopics),
 	// v158 -> v159
 	NewMigration("code comment replies should have the commitID of the review they are replying to", updateCodeCommentReplies),
+	// v159 -> v160
+	NewMigration("update reactions constraint", updateReactionConstraint),
 }
 
 // GetCurrentDBVersion returns the current db version

models/migrations/v159.go

@@ -0,0 +1,38 @@
+// Copyright 2020 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 (
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"xorm.io/xorm"
+)
+
+func updateReactionConstraint(x *xorm.Engine) error {
+	// Reaction represents a reactions on issues and comments.
+	type Reaction struct {
+		ID               int64              `xorm:"pk autoincr"`
+		Type             string             `xorm:"INDEX UNIQUE(s) NOT NULL"`
+		IssueID          int64              `xorm:"INDEX UNIQUE(s) NOT NULL"`
+		CommentID        int64              `xorm:"INDEX UNIQUE(s)"`
+		UserID           int64              `xorm:"INDEX UNIQUE(s) NOT NULL"`
+		OriginalAuthorID int64              `xorm:"INDEX UNIQUE(s) NOT NULL DEFAULT(0)"`
+		OriginalAuthor   string             `xorm:"INDEX UNIQUE(s)"`
+		CreatedUnix      timeutil.TimeStamp `xorm:"INDEX created"`
+	}
+
+	sess := x.NewSession()
+	defer sess.Close()
+
+	if err := sess.Begin(); err != nil {
+		return err
+	}
+
+	if err := recreateTable(sess, &Reaction{}); err != nil {
+		return err
+	}
+
+	return sess.Commit()
+}