I have the following lines to get a core_config_data value in a mysql upgrade script
$installer = $this;
$installer->startSetup();
$adapter = $installer->getConnection();
$my_store = Mage::getModel("core/store")->load("my_store", "code");
$templatePath = 'foo/bar';
$config_value = Mage::getStoreConfig($templatePath, $my_store);
if I debug $config_value I get null. However if I add this to a controller action I get the expected value. So it seems that I can't retrieve a config value from within a mysql upgrade script?