我们最近将Percona 5.5 SQL服务器升级到Percona 5.7。目前为止一切都很好。不幸的是，我们有一个巨大的查询，在5.7下执行速度极慢。在5.5下，即使使用sql_no_cache，它也只需要不到1秒钟的时间。在Percona 5.7下，执行这个查询需要长达1分钟的时间。奇怪的是，使用更多的组合索引会使查询变得更慢。删除所有组合索引将导致执行时间为30秒。强制使用sql_straight_join可以使查询在不到1秒钟的时间内运行。
因此，这里是查询语句：
因此，这里是查询语句：
SELECT t0_.tree_id AS tree_id0, t1_.treetype_name AS treetype_name1, c2_.contentelement_id AS contentelement_id2, t0_.tree_name AS tree_name3, (CASE WHEN t3_.treetype_name <> 'global' THEN t4_.tree_name ELSE t0_.tree_name END) AS sclr4, p5_.picture_id AS picture_id5, t6_.tree_misc_value_text AS tree_misc_value_text6, (CASE WHEN t3_.treetype_name <> 'global' THEN t7_.tree_misc_value_text ELSE t6_.tree_misc_value_text END) AS sclr7, w8_.widgetgeneral_slug AS widgetgeneral_slug8, (CASE WHEN t3_.treetype_name <> 'global' THEN w9_.widgetgeneral_slug ELSE w8_.widgetgeneral_slug END) AS sclr9, t10_.tree_misc_value_text AS tree_misc_value_text10, t11_.tree_misc_value_text AS tree_misc_value_text11
FROM tree_relation t12_
INNER JOIN tree t4_ ON t12_.tree_relation_parent = t4_.tree_id
INNER JOIN treetype t3_ ON t4_.tree_type_id = t3_.treetype_id AND (t3_.treetype_name IN ('global', 'country'))
INNER JOIN contentelement c13_ ON t4_.tree_id = c13_.contentelement_tree_id
INNER JOIN contentleaf c14_ ON c13_.contentelement_contentleaf_id = c14_.contentleaf_id AND (c14_.contentleaf_contentbranch_id = 1)
INNER JOIN widgetgeneral w9_
INNER JOIN widgetabstract w15_ ON w9_.widgetabstract_id = w15_.widgetabstract_id AND (w15_.widgetabstract_contentelement_id = c13_.contentelement_id AND w15_.widgetabstract_discriminator IN ('general') AND w15_.widgetabstract_state = 'preview')
INNER JOIN tree t0_ ON t12_.tree_relation_child = t0_.tree_id
INNER JOIN treetype t1_ ON t0_.tree_type_id = t1_.treetype_id AND (t1_.treetype_name IN ('city','region'))
INNER JOIN contentelement c2_ ON t0_.tree_id = c2_.contentelement_tree_id
INNER JOIN contentleaf c16_ ON c2_.contentelement_contentleaf_id = c16_.contentleaf_id AND (c16_.contentleaf_contentbranch_id = 1)
INNER JOIN widgetgeneral w8_
INNER JOIN widgetabstract w17_ ON w8_.widgetabstract_id = w17_.widgetabstract_id AND (w17_.widgetabstract_contentelement_id = c2_.contentelement_id AND w17_.widgetabstract_discriminator IN ('general') AND w17_.widgetabstract_state = 'preview')
INNER JOIN widgetgeneral w18_
INNER JOIN widgetabstract w19_ ON w18_.widgetabstract_id = w19_.widgetabstract_id AND (w19_.widgetabstract_contentleaf_id = c16_.contentleaf_id AND w19_.widgetabstract_discriminator IN ('general') AND w19_.widgetabstract_state = 'preview')
LEFT JOIN picture p5_ ON t0_.tree_picture_id = p5_.picture_id
LEFT JOIN tree_misc t6_ ON t0_.tree_id = t6_.tree_misc_tree_id AND (t6_.tree_misc_attributetype_key = 'flagId')
LEFT JOIN tree_misc t7_ ON t4_.tree_id = t7_.tree_misc_tree_id AND (t7_.tree_misc_attributetype_key = 'flagId')
LEFT JOIN tree_misc t10_ ON t0_.tree_id = t10_.tree_misc_tree_id AND (t10_.tree_misc_attributetype_key = 'latitude')
LEFT JOIN tree_misc t11_ ON t0_.tree_id = t11_.tree_misc_tree_id AND (t11_.tree_misc_attributetype_key = 'longitude')
WHERE w17_.widgetabstract_visibility = 'active' OR (w17_.widgetabstract_visibility = 'parent' AND w19_.widgetabstract_visibility = 'active')
对于版本 5.7 的说明：
我们尝试过升级以及完整的空白安装。开启和关闭了所有 SQL 模式和查询优化器选项。如果您需要更多信息或服务器变量，请告知。
操作系统：Debian GNU/Linux 8 (jessie) 服务器版本为：5.7.14-7-log Percona Server (GPL)，Release '7'，Revision '083e298'
也许您有我们缺失的提示。
编辑： 添加配置
[mysqld]
port = 3306
user = mysql
socket = /var/run/mysqld/mysqld.sock
pid-file = /var/run/mysqld/mysqld.pid
basedir = /usr
datadir = /var/lib/mysql
tmpdir = /tmp
lc-messages-dir = /usr/share/mysql
max_connect_errors = 1000000
log-error = /var/log/mysql/error.log
skip-external-locking
myisam-recover-options = BACKUP
character-set-server = utf8
collation-server = utf8_general_ci
interactive_timeout = 28800
wait_timeout = 28800
skip-name-resolve
group_concat_max_len = 268435456
innodb_file_per_table
innodb_buffer_pool_size = 48G
innodb_buffer_pool_instances = 1
innodb_flush_log_at_trx_commit = 1
innodb_data_file_path = ibdata1:2G:autoextend
innodb_log_file_size = 256M
innodb_log_buffer_size = 64M
innodb_file_format = barracuda
innodb_flush_method = O_DIRECT[mysqld_safe]
syslog
numa_interleave
# Per Thread
sort_buffer_size = 4M
read_buffer_size = 2M
# Cache/connection relevant
thread_cache_size = 850
table_open_cache = 4048
max_connections = 1300
# MyISAM settings (also valid for queries with temporary tables)
key_buffer_size = 128M
myisam_sort_buffer_size = 16M
# Misc
max_allowed_packet = 256M
max_heap_table_size = 16M
thread_stack = 192K
tmp_table_size = 16M
# Query cache
query_cache_limit = 5M
query_cache_size = 4024M
server-id = 102
log_bin = /var/log/mysql/mysql-bin.log
binlog_format = mixed
expire_logs_days = 10
max_binlog_size = 100M
# enforce syncing of every transation to binlog (crash safe, with bbu this should be fast)
sync_binlog = 1
sync_relay_log = 1
sync_master_info = 1
sync_relay_log_info = 1
relay-log = mysqld-relay-bin
skip-slave-start
log-slave-updates
slow_query_log = 1
slow_query_log_file = /var/log/mysql/mysql-slow.log
long_query_time = 1
log-queries-not-using-indexes
编辑2：
为5.5添加解释。
innodb_buffer_pool_size的值。仅仅添加索引并不能使查询变得更快。 - MjhEXPLAIN吗？这可能会更容易地看出哪些优化出了问题。 - Rick Jamesw15_。 - Rick James