protected function appendCustomizeGlobalExtra( $globalExtraCss, $schema = null )
    {
        $where = array( 'rootParagraphId' => null );
        $table = 'customize_extra';

        if ( $schema )
        {
            $table = array( $schema, $table );
        }

        $current = $this->selectFromTable(
            $table,
            'extra',
            $where
        );

        if ( null === $current )
        {
            $update = $this->updateTable(
                $table,
                array(
                    'extra' => $globalExtraCss,
                ),
                $where
            );

            if ( ! $update )
            {
                return (bool) $this->insertIntoTable(
                    $table,
                    array(
                        'rootParagraphId'   => null,
                        'extra'             => $globalExtraCss,
                    ),
                    true
                );
            }

            return (bool) $update;
        }

        return (bool) $this->updateTable(
            $table,
            array(
                'extra' => $current . "\n\n" . $globalExtraCss,
            ),
            $where
        );
    }