From d842060bc421322064c01818c4b1422b1f179137 Mon Sep 17 00:00:00 2001
From: black <hello.bug@foxmail.com>
Date: Tue, 27 Jun 2023 19:06:05 +0800
Subject: [PATCH] add comment

---
 schema/field.go | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/schema/field.go b/schema/field.go
index 8df568ab..04be47cf 100644
--- a/schema/field.go
+++ b/schema/field.go
@@ -69,7 +69,6 @@ type Field struct {
 	DefaultValueInterface  interface{}
 	NotNull                bool
 	Unique                 bool
-	UniqueIndex            string
 	Comment                string
 	Size                   int
 	Precision              int
@@ -88,6 +87,12 @@ type Field struct {
 	Set                    func(context.Context, reflect.Value, interface{}) error
 	Serializer             SerializerInterface
 	NewValuePool           FieldNewValuePool
+
+	// In some db (e.g. MySQL), Unique and UniqueIndex are indistinguishable.
+	// When a column has a (not Mul) UniqueIndex, Migrator always reports its gorm.ColumnType is Unique.
+	// It causes field unnecessarily migration.
+	// Therefore, we need to record the UniqueIndex on this column (exclude Mul UniqueIndex) for MigrateColumnUnique.
+	UniqueIndex string
 }
 
 func (field *Field) BindName() string {