我在VPS上运行Prestashop 1.6驱动的电子商店，具有4GB RAM，2CPU，60GB SSD特性。目前我的商店里有大约20000种产品，我遇到网站加载问题，因为mysql查询运行时间很长。当我运行 htop 来分析进程时，我发现mysql消耗了100％的CPU。这是 mysqltuner ：
的输出-------- Performance Metrics -------------------------------------------------
[--] Up for: 1h 29m 9s (241K q [45.109 qps], 319 conn, TX: 318M, RX: 126M)
[--] Reads / Writes: 78% / 22%
[--] Total buffers: 192.0M global + 2.7M per thread (151 max threads)
[OK] Maximum possible memory usage: 597.8M (15% of installed RAM)
[OK] Slow queries: 0% (8/241K)
[OK] Highest usage of available connections: 2% (4/151)
[OK] Key buffer size / total MyISAM indexes: 16.0M/44.9M
[OK] Key buffer hit rate: 99.6% (36M cached / 133K reads)
[OK] Query cache efficiency: 49.6% (101K cached / 205K selects)
[!!] Query cache prunes per day: 1386761
[OK] Sorts requiring temporary tables: 0% (1 temp sorts / 7K sorts)
[!!] Joins performed without indexes: 78
[OK] Temporary tables created on disk: 8% (846 on disk / 9K total)
[OK] Thread cache hit rate: 98% (4 created / 319 connections)
[!!] Table cache hit rate: 10% (340 open / 3K opened)
[OK] Open file limit used: 62% (643/1K)
[OK] Table locks acquired immediately: 100% (239K immediate / 239K locks)
-------- Recommendations -----------------------------------------------------
General recommendations:
Add skip-innodb to MySQL configuration to disable InnoDB
MySQL started within last 24 hours - recommendations may be inaccurate
Enable the slow query log to troubleshoot bad queries
Adjust your join queries to always utilize indexes
Increase table_cache gradually to avoid file descriptor limits
Variables to adjust:
query_cache_size (> 16M)
join_buffer_size (> 128.0K, or always use indexes with joins)
table_cache (> 400)
请建议任何优化方法。
修改
慢查询输出日志为here。
答案 0 :(得分：0)
以下是您日志中的第二个查询，查看其他查询。为了帮助解决这个问题，我进行了轻微的重构，以摆脱子查询并转变为INNER JOIN。此外，为了帮助其他人不了解您的表格，请始终将您的字段引用限定为table.column或alias.column，以便知道您的level_depth，nleft，nright来自哪里。它可能有助于索引。
对于索引，我会在每个表中使用以下内容。
ps_category, index ON( active, id_category, id_lang, nleft, nright, level_depth )
ps_category_lang, index ON( id_category, id_shop, id_lang )
ps_category_shop, index ON( id_category, id_shop )
ps_category_group, index ON( id_category, id_group )
ps_lang, index ON( id_lang, active )
略微重写的查询
SELECT
c.id_parent,
c.id_category,
cl.name,
cl.description,
cl.link_rewrite
FROM
ps_category c
INNER JOIN ps_category_lang cl
ON c.id_category = cl.id_category
AND cl.id_shop = 1
AND cl.id_lang = 2
INNER JOIN ps_category_shop cs
ON c.id_category = cs.id_category
AND cs.id_shop = 1
INNER JOIN ps_category_group psg
ON c.id_category = psg.id_category
AND psg.id_group = 1
WHERE
( c.active = 1
OR c.id_category = 2)
AND c.id_category != 1
AND level_depth <= 7
AND nleft >= 350 AND nright <= 351
ORDER BY
level_depth ASC,
cs.position ASC;
第三个查询。请注意，在这种情况下，特定的一些关键元素被移动到顶部，因此我也将它们放在键索引中，然后在where子句中使用其他元素（主要是可读性调整，但有助于查看＆＃34;特定＆ ＃34;索引优势的元素）
SELECT
c.id_category,
cl.name,
cl.link_rewrite
FROM
ps_category c
LEFT JOIN ps_category_lang cl
ON c.id_category = cl.id_category
AND cl.id_shop = 1
INNER JOIN ps_category_shop category_shop
ON c.id_category = category_shop.id_category
AND category_shop.id_shop = 1
WHERE
c.active = 1
AND cl.id_lang = 2
AND c.nleft between 2 and 350
AND c.nright between 351 and 625
AND c.level_depth > 1
ORDER BY
c.level_depth ASC;
你需要确认你真正想要的下一个查询...你有一个左连接到语言表，但然后添加＆＃34; AND l.active = 1＆＃34;在where子句中实际上会把它变成INNER JOIN。如果你真的想要LEFT-JOIN，请将l.active移动到连接部分，例如我在此处调整
SELECT
l.id_lang,
c.link_rewrite
FROM
ps_category_lang AS c
LEFT JOIN ps_lang AS l
ON c.id_lang = l.id_lang
AND l.active = 1
WHERE
c.id_category = 324
希望这些索引以及查询的示例澄清/可读性可能有助于改进日志。如果仍有其他问题，请根据需要发布。
修改慢速日志报告中的第一个查询
在第一个查询中，您似乎正在寻找特定产品商店的内容。但是，您将使用产品类别开始查询，然后左键加入产品，然后加入产品商店。由于这些产品最终将通过where与特定类别相关联，因此无论如何都会创建INNER JOIN。我会稍微重组如下
我会在ps_product_shop ON上有一个索引（id_shop，active，visibility，id_product，id_category_default）
SELECT
p.*,
ps.*,
stock.out_of_stock,
IFNULL(stock.quantity, 0) as quantity,
MAX(pas.id_product_attribute) id_product_attribute,
pas.minimal_quantity AS product_attribute_minimal_quantity,
pl.description,
pl.description_short,
pl.available_now,
pl.available_later,
pl.link_rewrite,
pl.meta_description,
pl.meta_keywords,
pl.meta_title,
pl.name,
MAX(image_shop.id_image) id_image,
il.legend,
m.name AS manufacturer_name,
cl.name AS category_default,
DATEDIFF(ps.`date_add`, DATE_SUB(NOW(),INTERVAL 20 DAY)) > 0 AS new,
ps.price AS orderprice
FROM
( select @thisLanguage := 1 ) sqlvars,
ps_product_shop ps
INNER JOIN ps_product p
ON ps.id_product = p.id_product
INNER JOIN ps_category_product cp
ON id_product = cp.id_product
AND cp.id_category = 2
LEFT JOIN ps_product_attribute pa
ON p.id_product = pa.id_product
LEFT JOIN ps_product_attribute_shop pas
ON pa.id_product_attribute = pas.id_product_attribute
AND ps.id_shop = pas.id_shop
AND pas.default_on = 1
LEFT JOIN ps_stock_available stock
ON p.id_product = stock.id_product
AND ps.id_shop = stock.id_shop
AND stock.id_shop_group = 0
AND stock.id_product_attribute = IFNULL(pas.id_product_attribute, 0)
LEFT JOIN ps_product_lang pl
ON p.id_product = pl.id_product
AND ps.id_shop = pl.id_shop
AND pl.id_lang = @thisLanguage
LEFT JOIN ps_image i
ON p.id_product = i.id_product
LEFT JOIN ps_image_shop image_shop
ON i.id_image = image_shop.id_image
AND ps.id_shop = image_shop.id_shop
AND image_shop.cover = 1
LEFT JOIN ps_image_lang il
ON image_shop.id_image = il.id_image
AND il.id_lang = @thisLanguage
LEFT JOIN ps_manufacturer m
ON p.id_manufacturer = m.id_manufacturer
LEFT JOIN ps_category_lang cl
ON ps.id_category_default = cl.id_category
AND cl.id_shop = ps.id_shop
AND cl.id_lang = @thisLanguage
WHERE
ps.id_shop = 1
AND ps.active = 1
AND ps.visibility IN ("both", "catalog")
GROUP BY
ps.id_product
ORDER BY
cp.position ASC
LIMIT
0,8;
至于将多字段索引创建为单个索引，例如：
CREATE INDEX act_id_lang ON ps_category（active，id_category，id_lang，nleft，nright，level_depth）;
在任何表格上给出一个简单的索引名称...使用所有键，因为它们在查询中会有效。
答案 1 :(得分：0)
您应该在更长的使用时间后使用mysqltuner。 这应该删除以下消息： MySQL在过去24小时内启动 - 建议可能不准确