Cake\Database\Schema\PostgresSchema::_keySql PHP Method

    protected function _keySql($prefix, $data)
    {
        $columns = array_map([$this->_driver, 'quoteIdentifier'], $data['columns']);
        if ($data['type'] === Table::CONSTRAINT_FOREIGN) {
            return $prefix . sprintf(' FOREIGN KEY (%s) REFERENCES %s (%s) ON UPDATE %s ON DELETE %s DEFERRABLE INITIALLY IMMEDIATE', implode(', ', $columns), $this->_driver->quoteIdentifier($data['references'][0]), $this->_convertConstraintColumns($data['references'][1]), $this->_foreignOnClause($data['update']), $this->_foreignOnClause($data['delete']));
        }
        return $prefix . ' (' . implode(', ', $columns) . ')';
    }