Import time improvment

Instead of making as many queries as you ps_feature entries (for each
product), it is possible to make it in one query.

And we test if the user has the MySQL rights to create temporary tables.

classes/Feature.php

@@ -313,19 +313,30 @@ class FeatureCore extends ObjectModel
 	public static function cleanPositions()
 	{
 		$return = true;
-
 		$sql = '
-		SELECT `id_feature`
+			CREATE TEMPORARY TABLE `'._DB_PREFIX_.'feature_tmp` (
-		FROM `'._DB_PREFIX_.'feature`
+			`rank` INT NOT NULL AUTO_INCREMENT,
-		ORDER BY `position`';
+			`id_feature` int not null,
-		$result = Db::getInstance()->executeS($sql);
+				`position` int not null,
+				primary key(rank)
+			);
+			INSERT INTO '._DB_PREFIX_.'feature_tmp(id_feature,position) SELECT id_feature,position FROM '._DB_PREFIX_.'feature ORDER BY position ASC;
+			UPDATE `'._DB_PREFIX_.'feature` f LEFT JOIN '._DB_PREFIX_.'feature_tmp t USING(id_feature) SET f.position = rank-1';
+		$return = Db::getInstance()->executeS($sql);
+		if (!$return) {
+			$sql = '
+			SELECT `id_feature`
+			FROM `'._DB_PREFIX_.'feature`
+			ORDER BY `position`';
+			$result = Db::getInstance()->executeS($sql);
 
-		$i = 0;
+			$i = 0;
-		foreach ($result as $value)
+			foreach ($result as $value)
-			$return = Db::getInstance()->execute('
+				$return = Db::getInstance()->execute('
-			UPDATE `'._DB_PREFIX_.'feature`
+				UPDATE `'._DB_PREFIX_.'feature`
-			SET `position` = '.(int)$i++.'
+				SET `position` = '.(int)$i++.'
-			WHERE `id_feature` = '.(int)$value['id_feature']);
+				WHERE `id_feature` = '.(int)$value['id_feature']);
+		}
 		return $return;
 	}