/**
* Fetch constraint information from the database
*
* Invoked by the constructor, the default implementation queries
* information_schema.table_constraints and information_schema.key_column_usage.
* To make this functional, subclasses must set
* \Nada\Database\AbstractDatabase::$_tableSchema.
*
* Only primary keys are recognized for now. All other constraints are
* ignored.
*
* @todo Recognize other constraint types
*/
protected function _fetchConstraints()
{
$constraints = $this->_database->query(<<<EOT
SELECT kcu.column_name
FROM information_schema.key_column_usage kcu
JOIN information_schema.table_constraints tc
USING (table_schema, table_name, constraint_schema, constraint_name)
WHERE tc.constraint_type = 'PRIMARY KEY'
AND tc.table_schema = ?
AND LOWER(tc.table_name) = ?
ORDER BY kcu.ordinal_position
EOT
, array($this->_database->getTableSchema(), $this->_name));
foreach ($constraints as $constraint) {
$this->_primaryKey[] = $this->_columns[strtolower($constraint['column_name'])];
}
}
