// Common type names include "VARCHAR", "TEXT", "NVARCHAR", "DECIMAL", "BOOL",
// "INT", and "BIGINT".
func (ct ColumnType) DatabaseTypeName() string {
	if ct.DataTypeValue.Valid {
		return ct.DataTypeValue.String
	}
	return ct.SQLColumnType.DatabaseTypeName()
}

// ColumnType returns the database type of the column. like `varchar(16)`
func (ct ColumnType) ColumnType() (columnType string, ok bool) {

	CheckOption string // optional. e.g. `WITH [ CASCADED | LOCAL ] CHECK OPTION`
	Query       *DB    // required subquery.
}

// ColumnType column type interface
type ColumnType interface {
	Name() string
	DatabaseTypeName() string                 // varchar
	ColumnType() (columnType string, ok bool) // varchar(64)
	PrimaryKey() (isPrimaryKey bool, ok bool)
	AutoIncrement() (isAutoIncrement bool, ok bool)
	Length() (length int64, ok bool)

	AssertEqual(t, nil, err)
	AssertEqual(t, "varchar", ct.DatabaseTypeName())

	ct, err = findColumnType(&ArrayTypeModel{}, "text_array")
	AssertEqual(t, nil, err)
	AssertEqual(t, "text[]", ct.DatabaseTypeName())

	ct, err = findColumnType(&ArrayTypeModel{}, "nested_text_array")
	AssertEqual(t, nil, err)
	AssertEqual(t, "text[]", ct.DatabaseTypeName())

	if field.IgnoreMigration {
		return nil
	}

	// found, smart migrate
	fullDataType := strings.TrimSpace(strings.ToLower(m.DB.Migrator().FullDataTypeOf(field).SQL))
	realDataType := strings.ToLower(columnType.DatabaseTypeName())

	var (
		alterColumn bool
		isSameType  = fullDataType == realDataType
	)

	if !field.PrimaryKey {
		// check type
		if !strings.HasPrefix(fullDataType, realDataType) {

pkg database/sql/driver, type TxOptions struct, ReadOnly bool
pkg database/sql, func Named(string, interface{}) NamedArg
pkg database/sql, method (*ColumnType) DatabaseTypeName() string
pkg database/sql, method (*ColumnType) DecimalSize() (int64, int64, bool)
pkg database/sql, method (*ColumnType) Length() (int64, bool)
pkg database/sql, method (*ColumnType) Name() string