feat: support using DeleteId field for soft deletes

README.md

@@ -90,4 +90,25 @@ SELECT * FROM users WHERE is_del = 0;
 
 // Delete
 UPDATE users SET is_del = 1, deleted_at = /* current unix milli second second*/ WHERE ID = 1;
-```
+```
+
+## Mixed Mode with Delete ID Field
+#### Maintaining Unique Key Integrity
+This allows you to record the original ID of a deleted record in another field. By doing so, you can maintain the integrity of unique keys by allowing new records with the same unique key to be inserted without conflict.
+#### Example
+Assume we have a User model where the Email field needs to be unique. By storing the original ID in the DeletedId field and creating a composite unique key with Email and DeletedId, you can insert a new record without violating the unique constraint even after soft deleting an existing record.
+```go
+type User struct {
+ID            uint
+Name          string
+Email         string
+DeletedId     uint // Stores the original ID of the deleted record
+IsDel         soft_delete.DeletedAt    `gorm:"softDelete:flag,DeletedIDField:DeletedId,DeletedIDFromField:ID"` // use `1` `0`
+}
+
+// Query
+SELECT * FROM users WHERE is_del = 0;
+
+// Delete
+UPDATE users SET is_del = 1, deleted_id = /* value from ID */ WHERE ID = 1;
+```

soft_delete.go

@@ -73,6 +73,12 @@ func (DeletedAt) DeleteClauses(f *schema.Field) []clause.Interface {
 	if v := settings["DELETEDATFIELD"]; v != "" { // DeletedAtField
 		softDeleteClause.DeleteAtField = f.Schema.LookUpField(v)
 	}
+	if v := settings["DELETEDIDFIELD"]; v != "" { // DeleteIdField
+		softDeleteClause.DeleteIdField = f.Schema.LookUpField(v)
+	}
+	if v := settings["DELETEDIDFROMFIELD"]; v != "" { // DeleteIdFromField
+		softDeleteClause.DeleteIdFromField = f.Schema.LookUpField(v)
+	}
 	return []clause.Interface{softDeleteClause}
 }
 
@@ -101,10 +107,12 @@ func (sd SoftDeleteUpdateClause) ModifyStatement(stmt *gorm.Statement) {
 }
 
 type SoftDeleteDeleteClause struct {
-	Field         *schema.Field
-	Flag          bool
-	TimeType      schema.TimeType
-	DeleteAtField *schema.Field
+	Field             *schema.Field
+	Flag              bool
+	TimeType          schema.TimeType
+	DeleteAtField     *schema.Field
+	DeleteIdField     *schema.Field
+	DeleteIdFromField *schema.Field
 }
 
 func (sd SoftDeleteDeleteClause) Name() string {
@@ -135,6 +143,14 @@ func (sd SoftDeleteDeleteClause) ModifyStatement(stmt *gorm.Statement) {
 			stmt.SetColumn(deleteAtField.DBName, value, true)
 		}
 
+		deleteIdField := sd.DeleteIdField
+		deleteIdFromField := sd.DeleteIdFromField
+
+		if deleteIdField != nil && deleteIdFromField != nil {
+			set = append(set, clause.Assignment{Column: clause.Column{Name: deleteIdField.DBName}, Value: gorm.Expr(deleteIdFromField.DBName)})
+			stmt.SetColumn(deleteIdField.DBName, gorm.Expr(deleteIdFromField.DBName), true)
+		}
+
 		if sd.Flag {
 			set = append(clause.Set{{Column: clause.Column{Name: sd.Field.DBName}, Value: FlagDeleted}}, set...)
 			stmt.SetColumn(sd.Field.DBName, FlagDeleted, true)