/**
* Migrate Entries from source to target tables (if possible)
*
* TODO: Delete existing Select/Multiselect Values if the new Backend Type is not one of Select/Multiselect
*
* @param Mage_Eav_Model_Entity_Attribute $attribute Attribute Model
* @param string $targetType Target Backend Type
* @return void
*/
protected function _migrateData($attribute, $targetType)
{
/** @var Varien_Db_Adapter_Interface $_dbConnection */
$_dbConnection = Mage::getSingleton('core/resource')->getConnection('core_write');
// e.g. Entity is 'catalog_product'
$entityTypeCode = $attribute->getEntity()->getData('entity_type_code');
// Set Backend Types for later reference
$sourceType = $attribute->getBackendType();
// Create complete Entity Table names, e.g. 'catalog_product_entity_text'
$sourceTable = implode([$entityTypeCode, 'entity', $sourceType], '_');
$targetTable = implode([$entityTypeCode, 'entity', $targetType], '_');
// Select all existing entries for given Attribute
$srcSql = 'SELECT' . ' * FROM ' . $sourceTable . ' WHERE attribute_id = ? AND entity_type_id = ?';
/** @var Zend_Db_Statement_Interface $sourceQuery */
$sourceQuery = $_dbConnection->query($srcSql, [$attribute->getId(), $attribute->getEntity()->getData('entity_type_id')]);
$this->_migrateNonSelect($targetType, $sourceQuery, $sourceType, $targetTable, $_dbConnection, $sourceTable);
}