// RenameColumn rename value's field name from oldName to newName
func (m Migrator) RenameColumn(value interface{}, oldName, newName string) error {
	return m.RunWithValue(value, func(stmt *gorm.Statement) error {
		if stmt.Schema != nil {
			if field := stmt.Schema.LookUpField(oldName); field != nil {
				oldName = field.DBName
			}

			if field := stmt.Schema.LookUpField(newName); field != nil {
				newName = field.DBName
			}
		}

		t.Fatalf("Got error when tried to create index: %+v", err)
	}

	if err := DB.Migrator().RenameIndex(&IndexStruct{}, "idx_index_structs_name", "idx_users_name_1"); err != nil {
		t.Fatalf("no error should happen when rename index, but got %v", err)
	}

	if !DB.Migrator().HasIndex(&IndexStruct{}, "idx_users_name_1") {
		t.Fatalf("Should find index for user's name after rename")
	}

Jinzhu <******@****.***> 1582421928 +0800

	Name  string
	Field *Field
}

func (uni *UniqueConstraint) GetName() string { return uni.Name }

func (uni *UniqueConstraint) Build() (sql string, vars []interface{}) {
	return "CONSTRAINT ? UNIQUE (?)", []interface{}{clause.Column{Name: uni.Name}, clause.Column{Name: uni.Field.DBName}}
}

// ParseUniqueConstraints parse schema unique constraints
func (schema *Schema) ParseUniqueConstraints() map[string]UniqueConstraint {

							relFields = append(relFields, rel.Field)
							for _, name := range names[1 : subNameCount-1] {
								rel = rel.FieldSchema.Relationships.Relations[name]
								relFields = append(relFields, rel.Field)
							}
							// lastest name is raw dbname
							dbName := names[subNameCount-1]
							if field := rel.FieldSchema.LookUpField(dbName); field != nil && field.Readable {
								fields[idx] = field

		onConflict     = onConflictOption(db.Statement, rel.FieldSchema, defaultUpdatingColumns)
		refName        = rel.Name + "."
		values         = rValues.Interface()
	)

	for name, ok := range selectColumns {
		columnName := ""
		if strings.HasPrefix(name, refName) {
			columnName = strings.TrimPrefix(name, refName)
		}

		if columnName != "" {
			if ok {
				selects = append(selects, columnName)

				} else if f := db.Statement.Schema.LookUpField(name); f != nil {
					clauseSelect.Columns[idx] = clause.Column{Name: f.DBName}
				} else {
					clauseSelect.Columns[idx] = clause.Column{Name: name, Raw: true}
				}
			}
		} else if db.Statement.Schema != nil && len(db.Statement.Omits) > 0 {
			selectColumns, _ := db.Statement.SelectAndOmitColumns(false, false)

			}

			for _, field := range stmt.Schema.FieldsWithDefaultDBValue {
				if v, ok := selectColumns[field.DBName]; (ok && v) || (!ok && !restricted) && field.DefaultValueInterface == nil {
					if rvOfvalue, isZero := field.ValueOf(stmt.Context, stmt.ReflectValue); !isZero {
						values.Columns = append(values.Columns, clause.Column{Name: field.DBName})
						values.Values[0] = append(values.Values[0], rvOfvalue)
					}
				}
			}
		default:

		if len(tx.Statement.Selects) == 1 {
			dbName := tx.Statement.Selects[0]
			fields := strings.FieldsFunc(dbName, utils.IsValidDBNameChar)
			if len(fields) == 1 || (len(fields) == 3 && (strings.ToUpper(fields[1]) == "AS" || fields[1] == ".")) {
				if tx.Statement.Parse(tx.Statement.Model) == nil {
					if f := tx.Statement.Schema.LookUpField(dbName); f != nil {
						dbName = f.DBName
					}
				}

						foreignFields = append(foreignFields, ref.PrimaryKey)
						relForeignKeys = append(relForeignKeys, ref.ForeignKey.DBName)
					} else if ref.PrimaryValue != "" {
						queryConds = append(queryConds, clause.Eq{
							Column: clause.Column{Table: rel.JoinTable.Table, Name: ref.ForeignKey.DBName},
							Value:  ref.PrimaryValue,
						})
					}
				}