Magento 不支持模块的卸载/降级有什么原因吗

I have seen some postings in regards to such and have investigated the same scenarios for SQL deployment myself. I would have to agree that being Enterprise grade Magento should have this type of functionality built-in. The good news it IS, at least in SOME form or fashion, how complete it is I'm not really sure. Here's a sample of a rollback upon exception:

try {
    $write = Mage::getSingleton('core/resource')->getConnection('core_write');
    $write->beginTransaction();

// do stuff here

    $write->commit();
} catch (Exception $e) {
    mage::log(__METHOD__ . ':' . __LINE__ . ': Rollback happened.');
    $write->rollback();
}

现在，如果您查看 app/code/core/Mage/Core/Model/Resource/Setup.php，您会发现很多有趣的方法.特别是:_getModifySqlFiles、_rollbackResourceDb 和 _modifyResourceDb.

// Read resource files
$arrAvailableFiles = array();
$sqlDir = dir($sqlFilesDir);
while (false !== ($sqlFile = $sqlDir->read())) {
    $matches = array();
    if (preg_match('#^'.$resModel.'-'.$actionType.'-(.*).(sql|php)$#i', $sqlFile, $matches)) {
        $arrAvailableFiles[$matches[1]] = $sqlFile;
    }
}

$arrModifyFiles = $this->_getModifySqlFiles($actionType, $fromVersion, $toVersion, $arrAvailableFiles);

protected function _getModifySqlFiles($actionType, $fromVersion, $toVersion, $arrFiles)
{
    $arrRes = array();

    switch ($actionType) {
        case 'install':
        case 'data-install':
...
        case 'rollback':
            break;

        case 'uninstall':
            break;
    }
    return $arrRes;
}