function creer_champs_extras($champs, $nom_meta_base_version, $version_cible) {
	$current_version = 0.0;

	if ((!isset($GLOBALS['meta'][$nom_meta_base_version]))
	|| (($current_version = $GLOBALS['meta'][$nom_meta_base_version])!=$version_cible)){

		// cas d'une installation
		if ($current_version==0.0){
			include_spip('base/create');
			// on recupere juste les differentes tables a mettre a jour
			$tables = array();
			foreach ($champs as $c){ 
				if ($table = table_objet_sql($c->table)) {
					$tables[$table] = $table;
				}
			}		
			// on met a jour les tables trouvees
			foreach($tables as $table) {
				maj_tables($table);
			}
			ecrire_meta($nom_meta_base_version,$current_version=$version_cible,'non');
		}
	}	
}

function vider_champs_extras($champs, $nom_meta_base_version) {
	// on efface chaque champ trouve
	foreach ($champs as $c){ 
		if ($table = table_objet_sql($c->table) and $c->champ and $c->sql) {
			sql_alter("TABLE $table DROP $c->champ");
		}
	}
	effacer_meta($nom_meta_base_version);	
}