我在理解在嵌套集模型上使用什么索引时遇到了一些麻烦.查询是:
SELECT `node`.`id`,(COUNT(parent.id) - 1) AS `depth`,`name` FROM `categories` AS `parent`
INNER JOIN `categories` AS `node` ON (`node`.`lft` BETWEEN parent.lft AND parent.rgt)
INNER JOIN `filebank_categories` ON (`node`.`id` = `filebank_categories`.`category_id` AND `filebank_categories`.`filebank_id` = 136)
INNER JOIN `categories_names` ON (`categories_names`.`category_id` = `node`.`id` AND `categories_names`.`language_id` = 1)
WHERE `node`.`system_id` = parent.system_id
GROUP BY node.id
ORDER BY `node`.`lft` ASC
这个查询需要大约350毫秒,大约有5000行categories.EXPLAIN给出了这个:
1 SIMPLE filebank_categories ref fk_filebank_categories_categories1,filebank_id filebank_id 5 const 474 Using where; Using temporary; Using filesort 1 SIMPLE node eq_ref PRIMARY,lft,category,cat,lft,rgt,system,id,lft,system PRIMARY 4 …