Hi, we upgraded MariaDB 5.5 to 10.0 on one server last night and are now dealing with severe performance issues. Here is one case where it's notable: Query - SELECT b.*, p.category_id FROM brands b JOIN products p USING(brand_id) GROUP BY category_id, brand_id ORDER BY title ASC; Table structures: CREATE TABLE `brands` ( `brand_id` int(11) NOT NULL AUTO_INCREMENT, `title` varchar(50) NOT NULL, `slug` varchar(50) NOT NULL, `description` text NOT NULL, `discount_suv_1` float NOT NULL, `discount_suv_2` float NOT NULL, `discount_van_1` float NOT NULL, `discount_van_2` float NOT NULL, `discount_orp_1` float NOT NULL, `discount_orp_2` float NOT NULL, PRIMARY KEY (`brand_id`) ) ENGINE=InnoDB AUTO_INCREMENT=150 DEFAULT CHARSET=utf8 CREATE TABLE `products` ( `product_id` int(11) NOT NULL AUTO_INCREMENT, `category_id` int(11) DEFAULT NULL, `featured_image_id` int(11) DEFAULT NULL, `brand_id` int(11) DEFAULT NULL, `title` text NOT NULL, `slug` text NOT NULL, `price` float NOT NULL, `custom_price` float NOT NULL, `description` text NOT NULL, `hidden` tinyint(1) NOT NULL, `homepage` tinyint(1) NOT NULL, `sale` tinyint(1) NOT NULL, `width` float NOT NULL, `height` int(11) NOT NULL, `diameter` int(11) NOT NULL, `resistance` varchar(50) NOT NULL, `breaking_distance` varchar(50) NOT NULL, `noise` varchar(50) NOT NULL, `ean` varchar(50) NOT NULL, `availability` char(1) NOT NULL, `li` varchar(15) NOT NULL, `si` varchar(15) NOT NULL, `classes` varchar(5) NOT NULL, `all_year` tinyint(1) NOT NULL, `type` char(3) NOT NULL, `holes_count` float NOT NULL, `pitch` float NOT NULL, `et` float NOT NULL, `code` varchar(50) NOT NULL, `custom` tinyint(1) NOT NULL, `car_type` varchar(100) NOT NULL, `models` text NOT NULL, `imported` tinyint(1) NOT NULL, `is_runflat` tinyint(1) NOT NULL, `stock_count` int(11) NOT NULL, `parser` char(1) NOT NULL, PRIMARY KEY (`product_id`), KEY `category_id` (`category_id`), KEY `featured_image_id` (`featured_image_id`), KEY `brand_id` (`brand_id`), KEY `slug` (`slug`(100)), KEY `hidden` (`hidden`), CONSTRAINT `products_ibfk_1` FOREIGN KEY (`category_id`) REFERENCES `categories` (`category_id`) ON DELETE SET NULL, CONSTRAINT `products_ibfk_4` FOREIGN KEY (`featured_image_id`) REFERENCES `product_images` (`product_image_id`) ON DELETE SET NULL, CONSTRAINT `products_ibfk_5` FOREIGN KEY (`brand_id`) REFERENCES `brands` (`brand_id`) ON DELETE SET NULL ) ENGINE=InnoDB AUTO_INCREMENT=63638 DEFAULT CHARSET=utf8 Table brands: 149 rows Table products: 62074 rows Query time on 5.5: about 0.2s Query time on 10.0: between 2 and 9s (if not cached) Explain on 5.5: http://watchdog.sk/5.5.png Explain on 10.0: http://watchdog.sk/10.png Any hints what's going on? What about the difference in the explain command? Thank you. azur