diff --git a/models/issue_reaction.go b/models/issue_reaction.go
index ad85e5747c3db..ae22f4443e429 100644
--- a/models/issue_reaction.go
+++ b/models/issue_reaction.go
@@ -18,12 +18,12 @@ import (
 // Reaction represents a reactions on issues and comments.
 type Reaction struct {
 	ID               int64              `xorm:"pk autoincr"`
-	Type             string             `xorm:"INDEX UNIQUE(s) NOT NULL"`
+	Type             string             `xorm:"VARCHAR(32) 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)"`
+	OriginalAuthor   string             `xorm:"VARCHAR(64) INDEX UNIQUE(s)"`
 	User             *User              `xorm:"-"`
 	CreatedUnix      timeutil.TimeStamp `xorm:"INDEX created"`
 }
diff --git a/models/migrations/migrations.go b/models/migrations/migrations.go
index 3227f6f75451b..e0e7e6ef4c17a 100644
--- a/models/migrations/migrations.go
+++ b/models/migrations/migrations.go
@@ -281,6 +281,8 @@ var migrations = []Migration{
 	NewMigration("Where Password is Valid with Empty String delete it", recalculateUserEmptyPWD),
 	// v167 -> v168
 	NewMigration("Add user redirect", addUserRedirect),
+	// v168 -> v169
+	NewMigration("Restrict user and reaction table index column size", restrictUserAndReactionColumnSize),
 }
 
 // GetCurrentDBVersion returns the current db version
diff --git a/models/migrations/v159.go b/models/migrations/v159.go
index 68043b9412774..53dd4c5bfd9dc 100644
--- a/models/migrations/v159.go
+++ b/models/migrations/v159.go
@@ -14,12 +14,12 @@ 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"`
+		Type             string             `xorm:"VARCHAR(32) 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)"`
+		OriginalAuthor   string             `xorm:"VARCHAR(64) INDEX UNIQUE(s)"`
 		CreatedUnix      timeutil.TimeStamp `xorm:"INDEX created"`
 	}
 
diff --git a/models/migrations/v168.go b/models/migrations/v168.go
new file mode 100644
index 0000000000000..c8ea910e3135b
--- /dev/null
+++ b/models/migrations/v168.go
@@ -0,0 +1,27 @@
+// 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 (
+	"xorm.io/xorm"
+)
+
+func restrictUserAndReactionColumnSize(x *xorm.Engine) error {
+	type Reaction struct {
+		ID             int64  `xorm:"pk autoincr"`
+		Type           string `xorm:"VARCHAR(32) INDEX NOT NULL"`
+		OriginalAuthor string `xorm:"VARCHAR(64) INDEX"`
+	}
+	if err := x.Sync2(new(Reaction)); err != nil {
+		return err
+	}
+
+	type User struct {
+		ID        int64  `xorm:"pk autoincr"`
+		LowerName string `xorm:"VARCHAR(64) UNIQUE NOT NULL"`
+		Name      string `xorm:"VARCHAR(64) UNIQUE NOT NULL"`
+	}
+	return x.Sync2(new(User))
+}
diff --git a/models/user.go b/models/user.go
index 8147c9f62610b..06c652bc8b701 100644
--- a/models/user.go
+++ b/models/user.go
@@ -91,8 +91,8 @@ var (
 // User represents the object of individual and member of organization.
 type User struct {
 	ID        int64  `xorm:"pk autoincr"`
-	LowerName string `xorm:"UNIQUE NOT NULL"`
-	Name      string `xorm:"UNIQUE NOT NULL"`
+	LowerName string `xorm:"VARCHAR(64) UNIQUE NOT NULL"`
+	Name      string `xorm:"VARCHAR(64) UNIQUE NOT NULL"`
 	FullName  string
 	// Email is the primary email address (to be used for communication)
 	Email                        string `xorm:"NOT NULL"`