这个话题引起了我的好奇心。虽然已经有答案了,但我想分享一下我发现的东西,尽管我没有进行深入追踪。
无论缓存是否启用/禁用,表模式都会被缓存。
在保存过程中,它将被缓存。
Mage_Core_Model_Abstract -> save()
Mage_Core_Model_Resource_Db_Abstract -> save(Mage_Core_Model_Abstract $object)
Mage_Core_Model_Resource_Db_Abstract
public function save(Mage_Core_Model_Abstract $object)
{
...
$this->_prepareDataForSave($object);
...
}
protected function _prepareDataForSave(Mage_Core_Model_Abstract $object)
{
return $this->_prepareDataForTable($object, $this->getMainTable());
}
Mage_Core_Model_Resource_Abstract
protected function _prepareDataForTable(Varien_Object $object, $table)
{
$data = array();
$fields = $this->_getWriteAdapter()->describeTable($table);
foreach (array_keys($fields) as $field) {
if ($object->hasData($field)) {
$fieldValue = $object->getData($field);
if ($fieldValue instanceof Zend_Db_Expr) {
$data[$field] = $fieldValue;
} else {
if (null !== $fieldValue) {
$fieldValue = $this->_prepareTableValueForSave($fieldValue, $fields[$field]['DATA_TYPE']);
$data[$field] = $this->_getWriteAdapter()->prepareColumnValue($fields[$field], $fieldValue);
} else if (!empty($fields[$field]['NULLABLE'])) {
$data[$field] = null;
}
}
}
}
return $data;
}
请看这行代码:$fields = $this->_getWriteAdapter()->describeTable($table);
该行代码涉及 IT 技术。
Varien_Db_Adapter_Pdo_Mysql
public function describeTable($tableName, $schemaName = null)
{
$cacheKey = $this->_getTableName($tableName, $schemaName);
$ddl = $this->loadDdlCache($cacheKey, self::DDL_DESCRIBE);
if ($ddl === false) {
$ddl = parent::describeTable($tableName, $schemaName);
$affected = array('tinyint', 'smallint', 'mediumint', 'int', 'bigint');
foreach ($ddl as $key => $columnData) {
if (($columnData['DEFAULT'] === '') && (array_search($columnData['DATA_TYPE'], $affected) !== FALSE)) {
$ddl[$key]['DEFAULT'] = null;
}
}
$this->saveDdlCache($cacheKey, self::DDL_DESCRIBE, $ddl);
}
return $ddl;
}
正如我们所看到的:
$ddl = $this->loadDdlCache($cacheKey, self::DDL_DESCRIBE);
将尝试从缓存中加载模式。
如果该值不存在:if ($ddl === false)
它将创建一个:$this->saveDdlCache($cacheKey, self::DDL_DESCRIBE, $ddl);
因此,如果我们曾经保存即将被更改(添加列等)的模型,则会发生本问题。
由于之前已经进行了$model->save()
,所以模式将被缓存。
稍后在添加新列并“保存”后,它将从缓存中加载模式(其中不包含新列),结果为:无法将新列的数据保存到数据库中。