Type.php

<?php
class ZendDbSchema_Validate_Db_Schema_Table_Mysql_Index_Type
    extends Zend_Validate_Abstract
{
    const NAME_EMPTY = 'indexTypeEmpty';
    const RENAME     = 'indexTypeRename';
    const INVALID    = 'indexTypeInvalid';

    protected $_messageTemplates = array(
        self::NAME_EMPTY => "Index type can not be empty",
        self::INVALID    => "Index type %value% is not a valid type",
        self::RENAME     => "Cannot change type of existing index"
    );

    protected $_indexesTypes = array(
        'FULLTEXT',
        'UNIQUE'
    );

    public function isValid($value)
    {
        $schema = null;
        if ($value instanceof ZendDbSchema_Db_Schema_Table_Index) {
            $schema = $value;
            $value = $schema->__get('type');
        }
        if (empty($value)) {
            $this->_error(self::NAME_EMPTY);
            return false;
        }
        if ($schema && $schema->isDirty('type')) {
            if ($schema->isExist()) {
                $this->_error(self::RENAME, $value);
                return false;
            }
            if (!in_array(strtoupper($value), $this->_indexesTypes)) {
                $this->_error(self::INVALID, $value);
                return false;
            }
        }
        return true;
    }
}