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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 {