}
		}
	}

	// check comment
	if comment, ok := columnType.Comment(); ok && comment != field.Comment {
		// not primary key
		if !field.PrimaryKey {
			alterColumn = true
		}
	}

	if alterColumn {
		if err := m.DB.Migrator().AlterColumn(value, field.DBName); err != nil {
			return err
		}
	}

	GetTables() (tableList []string, err error)
	TableType(dst interface{}) (TableType, error)

	// Columns
	AddColumn(dst interface{}, field string) error
	DropColumn(dst interface{}, field string) error
	AlterColumn(dst interface{}, field string) error
	MigrateColumn(dst interface{}, field *schema.Field, columnType ColumnType) error
	// MigrateColumnUnique migrate column's UNIQUE constraint, it's part of MigrateColumn.

	}
}

type CompanyNew struct {
	ID   int
	Name int
}

func TestAlterColumnDataType(t *testing.T) {
	DB.AutoMigrate(Company{})

	if err := DB.Table("companies").Migrator().AlterColumn(CompanyNew{}, "name"); err != nil {
		t.Fatalf("failed to alter column from string to int, got error %v", err)
	}

	DB.AutoMigrate(Company{})

	AssertEqual(t, nil, err)
	AssertEqual(t, "integer[]", ct.DatabaseTypeName())
}

type mockMigrator struct {
	gorm.Migrator
}

func (mm mockMigrator) AlterColumn(dst interface{}, field string) error {
	err := mm.Migrator.AlterColumn(dst, field)
	if err != nil {
		return err
	}
	return fmt.Errorf("trigger alter column error, field: %s", field)
}