mysql Ver 14.14使用readline 5.1为redhat-linux-gnu（x86_64）分发5.1.58
我正在接手一个旧项目。我被要求加快速度。我有启用慢查询日志。我正在检查slow-query-log中出现的查询。此查询需要10秒才能运行，并返回11,000行。
select
substring_index(ob1.literal,'/',1) AS sku4,
substring_index(
substring_index(ob1.literal,'/',2),'/',-(1)) AS sku5,
substring_index(
substring_index(ob1.literal,'/',3),'/',-(1)) AS sku6,
substring_index(ob2.literal,'/',1) AS sku7,
substring_index(
substring_index(ob2.literal,'/',2),'/',-(1)) AS sku8,
substring_index(
substring_index(ob2.literal,'/',3),'/',-(1)) AS sku9,concat_ws(',',ob.level_one,
substring_index(ob1.literal,'/',1),
substring_index(ob2.literal,'/',1)) AS sku1_filter,concat_ws(',',ob.level_two,
substring_index(
substring_index(ob1.literal,'/',2),'/',-(1)),
substring_index(
substring_index(ob2.literal,'/',2),'/',-(1))) AS sku2_filter,concat_ws(',',ob.level_three,
substring_index(
substring_index(ob1.literal,'/',3),'/',-(1)),
substring_index(
substring_index(ob2.literal,'/',3),'/',-(1))) AS sku3_filter,
t.title_id AS title_id,
t.us_list_price AS us_list_price,
t.uk_list_price AS uk_list_price,
t.can_list_price AS can_list_price,
t.aus_list_price AS aus_list_price,
t.min_age AS min_age,
t.max_age AS max_age,
t.book_club AS book_club,
t.best_seller AS best_seller,
t.award_winner AS award_winner,
t.asin AS asin,
t.format AS format,
ob.literal AS literal_1,
ob1.literal AS literal_2,
ob2.literal AS literal_3,
t.series AS series,
t.volume AS volume,
group_concat(distinct concat(u.first_name, ' ', u.last_name) separator ', ') AS marketer,
a.group_letter AS group_letter,
group_concat(distinct concat(u2.first_name, ' ', u2.last_name) separator ', ') AS editor,
oi.imprint_name AS imprint_name,
ob.level_one AS level_one,
ob.level_two AS level_two,
ob.level_three AS level_three,
ot1.territory_name AS rights,
(case when (isnull(t.active) or (t.active = ''))
then '' when (t.active = 'Y')
then 'Active' when (t.active = 'N')
then 'In Development' when (t.active = 'X')
then 'Terminated' when (t.active = 'T')
then 'Transmittal' end) AS status,
(case when (isnull(t.format) or (t.format = ''))
then '' when (t.format = 4)
then 'Ebook' when (t.format = 8)
then 'Print Book' when (t.format = 9)
then 'Audio Book' end) AS format_name,
t.title AS title,t.primary_isbn13 AS primary_isbn13,
group_concat(distinct a.display_name order by a.display_name ASC separator ', ') AS contributors,
group_concat(distinct c1.display_name order by c1.display_name ASC separator ', ') AS publishers,
t.publish_date AS pub_date,
group_concat(distinct g.name order by g.name ASC separator ', ') AS category,
group_concat(distinct g0.id order by g0.id ASC separator ', ') AS secondary_category_ids,
group_concat(distinct g0.name order by g0.name ASC separator ', ') AS secondary_categories
from ((((((((((((((((((((wawa_title t
left join wawa_title_to_imprint tti on((t.title_id = tti.title_id)))
left join wawa_imprint oi on((tti.imprint_id = oi.imprint_id)))
left join wawa_title_to_supplier t2a on((t2a.title_id = t.title_id)))
left join wawa_territories ot1 on((t.territory_id = ot1.territory_id)))
left join wawa_supplier a on((a.supplier_id = t2a.supplier_id)))
left join wawa_sku ob on((ob.code = t.sku1)))
left join wawa_sku ob1 on((ob1.code = t.sku2)))
left join wawa_sku ob2 on((ob2.code = t.sku3)))
left join bll_formats tf on((t.format = tf.id)))
left join bll_suppliers_to_wawa_editors aoe on((a.supplier_id = aoe.supplier_id)))
left join bll_suppliers_to_wawa_marketing_contacts amc on((a.supplier_id = amc.supplier_id)))
left join bll_contacts c0 on((c0.id = amc.id)))
left join users u on((amc.user_id = u.id)))
left join users u2 on((aoe.user_id = u2.id)))
join wawa_title_to_publisher t2p on((t2p.title_id = t.title_id)))
join wawa_publisher p on((p.publisher_id = t2p.publisher_id)))
join bll_contacts c1 on((c1.id = p.org_contact_id)))
left join wawa_title_to_genre t2g on((t2g.title_id = t.title_id)))
left join wawa_genres g on((g.id = t2g.genre_id_2)))
left join wawa_genres g0 on((g0.id = t2g.genre_id_3))) where ((t.title_id = t.title_id) and (t.active <> 'X'))
group by t.title_id
EXPLAIN的输出是：
+----+-------------+-------+--------+-----------------------------------------------------------------------------------------------+-------------------------------------+---------+------------------------------------------+------+----------------------------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------+--------+-----------------------------------------------------------------------------------------------+-------------------------------------+---------+------------------------------------------+------+----------------------------------------------+
| 1 | SIMPLE | p | index | PRIMARY,org_contact_fk | org_contact_fk | 5 | NULL | 66 | Using index; Using temporary; Using filesort |
| 1 | SIMPLE | c1 | eq_ref | PRIMARY | PRIMARY | 4 | wawa_ripple_development.p.org_contact_id | 1 | |
| 1 | SIMPLE | t2p | ref | idx_title_id,idx_publisher_id | idx_publisher_id | 4 | wawa_ripple_development.p.publisher_id | 66 | Using where |
| 1 | SIMPLE | t | eq_ref | PRIMARY,active_index,idx_title_active_isprimary | PRIMARY | 4 | wawa_ripple_development.t2p.title_id | 1 | Using where |
| 1 | SIMPLE | t2g | ref | idx_title_id | idx_title_id | 4 | wawa_ripple_development.t2p.title_id | 1 | |
| 1 | SIMPLE | g | eq_ref | PRIMARY | PRIMARY | 4 | wawa_ripple_development.t2g.genre_id_2 | 1 | |
| 1 | SIMPLE | g0 | eq_ref | PRIMARY | PRIMARY | 4 | wawa_ripple_development.t2g.genre_id_3 | 1 | |
| 1 | SIMPLE | tti | ref | PRIMARY | PRIMARY | 4 | wawa_ripple_development.t.title_id | 1 | Using index |
| 1 | SIMPLE | oi | eq_ref | PRIMARY | PRIMARY | 4 | wawa_ripple_development.tti.imprint_id | 1 | |
| 1 | SIMPLE | t2a | ref | title_id | title_id | 4 | wawa_ripple_development.t.title_id | 1 | Using index |
| 1 | SIMPLE | ot1 | eq_ref | PRIMARY | PRIMARY | 4 | wawa_ripple_development.t.territory_id | 1 | |
| 1 | SIMPLE | a | eq_ref | PRIMARY,wawa_supplier_venue_id_supplier_id | PRIMARY | 4 | wawa_ripple_development.t2a.supplier_id | 1 | |
| 1 | SIMPLE | ob | eq_ref | PRIMARY | PRIMARY | 29 | wawa_ripple_development.t.sku1 | 1 | |
| 1 | SIMPLE | ob1 | eq_ref | PRIMARY | PRIMARY | 29 | wawa_ripple_development.t.sku2 | 1 | |
| 1 | SIMPLE | ob2 | eq_ref | PRIMARY | PRIMARY | 29 | wawa_ripple_development.t.sku3 | 1 | |
| 1 | SIMPLE | tf | eq_ref | PRIMARY | PRIMARY | 4 | wawa_ripple_development.t.format | 1 | Using index |
| 1 | SIMPLE | aoe | ref | idx_by_supplier_and_editor,index_bll_suppliers_to_wawa_editors_on_supplier_id | idx_by_supplier_and_editor | 4 | wawa_ripple_development.a.supplier_id | 1 | Using index |
| 1 | SIMPLE | amc | ref | idx_by_supplier_and_marketing_contact,index_bll_suppliers_to_wawa_marketing_contacts_on_supplier_id | idx_by_supplier_and_marketing_contact | 4 | wawa_ripple_development.a.supplier_id | 1 | Using index |
| 1 | SIMPLE | c0 | eq_ref | PRIMARY | PRIMARY | 4 | wawa_ripple_development.amc.id | 1 | Using index |
| 1 | SIMPLE | u | eq_ref | PRIMARY | PRIMARY | 4 | wawa_ripple_development.amc.user_id | 1 | |
| 1 | SIMPLE | u2 | eq_ref | PRIMARY | PRIMARY | 4 | wawa_ripple_development.aoe.user_id | 1 | |
+----+-------------+-------+--------+-----------------------------------------------------------------------------------------------+-------------------------------------+---------+------------------------------------------+------+----------------------------------------------+
我担心两件事：
1。）使用索引;使用临时;使用filesort
2。）使用
我担心这些是对的吗？
有什么建议我可以做些什么来加快速度？
一些变数：
mysql> show variables like '%buffer%';
+-------------------------+---------+
| Variable_name | Value |
+-------------------------+---------+
| bulk_insert_buffer_size | 8388608 |
| innodb_buffer_pool_size | 8388608 |
| innodb_log_buffer_size | 1048576 |
| join_buffer_size | 131072 |
| key_buffer_size | 8384512 |
| myisam_sort_buffer_size | 8388608 |
| net_buffer_length | 16384 |
| preload_buffer_size | 32768 |
| read_buffer_size | 131072 |
| read_rnd_buffer_size | 262144 |
| sort_buffer_size | 2097144 |
| sql_buffer_result | OFF |
+-------------------------+---------+
答案 0 :(得分：2)
EXPLAIN中的位置并不表示哪个表确实需要tmp或filesort。有关详细信息，请参阅EXPLAIN FORMAT=JSON SELECT ...。WHERE使用了一定的效率;这仅适用于较新版本。EXPLAIN开始，它似乎经常接近1：1。至于加快速度......
LEFT吗？如果没有摆脱它;优化器可能更喜欢其他一些表。EXPLAIN表示需要获取的行数不多。 （注意：解释的“行”数字是近似的。）所以，我在这里看不到多少帮助。JOINs制作“覆盖索引” - 但仅针对“ref”案例，而不是“eq_ref + PRIMARY”案例。看起来你已经完成了这项工作。SHOW VARIABLES LIKE '%buffer%'; - 我正在寻找memory utilization。JOIN + GROUP BY - 这通常意味着行爆炸，然后是内爆。将JOIN中的部分更改为SELECT 中的子查询可以改进：( SELECT ... FROM ... WHERE ... LIMIT 1 ) AS whatever。TEXT？这迫使“filesort”内存不足（因此，速度较慢）。给我更多细节，也许我们可以解决它。总之，EXPLAIN看起来很干净。 JOINs的数量巨大是另一回事。
两个可能错误的架构设计：
<强>附加物
对于16GB的RAM以及InnoDB和MyISAM的混合，建议key_buffer_size = 1500M和innodb_buffer_pool_size = 5G。在my.cnf（或my.ini）中设置这些内容并重新启动mysqld。