Zend_Db_Table_Abstract::_setupPrimaryKey PHP Method

    protected function _setupPrimaryKey()
    {
        if (!$this->_primary) {
            $this->_setupMetadata();
            $this->_primary = array();
            foreach ($this->_metadata as $col) {
                if ($col['PRIMARY']) {
                    $this->_primary[$col['PRIMARY_POSITION']] = $col['COLUMN_NAME'];
                    if ($col['IDENTITY']) {
                        $this->_identity = $col['PRIMARY_POSITION'];
                    }
                }
            }
            // if no primary key was specified and none was found in the metadata
            // then throw an exception.
            if (empty($this->_primary)) {
                require_once 'Zend/Db/Table/Exception.php';
                throw new Zend_Db_Table_Exception('A table must have a primary key, but none was found');
            }
        } else {
            if (!is_array($this->_primary)) {
                $this->_primary = array(1 => $this->_primary);
            } else {
                if (isset($this->_primary[0])) {
                    array_unshift($this->_primary, null);
                    unset($this->_primary[0]);
                }
            }
        }
        $cols = $this->_getCols();
        if (!array_intersect((array) $this->_primary, $cols) == (array) $this->_primary) {
            require_once 'Zend/Db/Table/Exception.php';
            throw new Zend_Db_Table_Exception("Primary key column(s) (" . implode(',', (array) $this->_primary) . ") are not columns in this table (" . implode(',', $cols) . ")");
        }
        $primary = (array) $this->_primary;
        $pkIdentity = $primary[(int) $this->_identity];
        /**
         * Special case for PostgreSQL: a SERIAL key implicitly uses a sequence
         * object whose name is "<table>_<column>_seq".
         */
        if ($this->_sequence === true && $this->_db instanceof Zend_Db_Adapter_Pdo_Pgsql) {
            $this->_sequence = $this->_db->quoteIdentifier("{$this->_name}_{$pkIdentity}_seq");
            if ($this->_schema) {
                $this->_sequence = $this->_db->quoteIdentifier($this->_schema) . '.' . $this->_sequence;
            }
        }
    }

 protected function _setupPrimaryKey()
 {
     if (empty($this->_primary)) {
         $this->_primary = 'id';
     }
     parent::_setupPrimaryKey();
 }