如何将 Laravel SQl 查询时间保持在 5 秒以下
How to Keep Laravel SQl Query Time Under 5 seconds
我的 php 应用程序使用 laravel 4.1.31。对于数据库查询，它通过ajax使用knockout js库。当数据库变大时，ajax加载成为一个问题，因为加载时间太长，有时会中途停止。我不熟悉这些库，所以我无法进行任何应用程序级别的优化。
我希望我仍然可以对数据库查询进行优化，并将每个查询控制在 5 秒以内。
以下是我可以分享的一些信息：
内存：2GB 1core Debian 9。
单个 Innodb 数据库。
慢查询日志：
# Time: 190611 7:49:08
# User@Host: user[user] @ localhost []
# Thread_id: 690728 Schema: user QC_hit: No
# Query_time: 9.343611 Lock_time: 0.000030 Rows_sent: 100 Rows_examined: 440481
# Rows_affected: 0
use user;
SET timestamp=1560239348;
select * from `titles` where `titles`.`type` = 'movie'
order by `tmdb_rating` desc limit 100 offset 86500;
显示创建 TABLE 个标题；
CREATE TABLE `titles` (
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`title` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`type` enum('movie','series') COLLATE utf8_unicode_ci DEFAULT NULL,
`imdb_rating` varchar(10) COLLATE utf8_unicode_ci DEFAULT NULL,
`tmdb_rating` varchar(10) COLLATE utf8_unicode_ci DEFAULT NULL,
`mc_user_score` varchar(10) COLLATE utf8_unicode_ci DEFAULT NULL,
`mc_critic_score` smallint(5) unsigned DEFAULT NULL,
`mc_num_of_votes` int(10) unsigned DEFAULT NULL,
`imdb_votes_num` bigint(20) unsigned DEFAULT NULL,
`release_date` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`year` smallint(5) unsigned DEFAULT NULL,
`plot` text COLLATE utf8_unicode_ci,
`genre` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`tagline` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`poster` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`background` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`awards` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`runtime` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`trailer` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`budget` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`revenue` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`views` bigint(20) NOT NULL DEFAULT '1',
`tmdb_popularity` float(50,2) unsigned DEFAULT NULL,
`imdb_id` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`tmdb_id` bigint(20) unsigned DEFAULT NULL,
`season_number` tinyint(3) unsigned DEFAULT NULL,
`fully_scraped` tinyint(3) unsigned NOT NULL DEFAULT '0',
`allow_update` tinyint(3) unsigned NOT NULL DEFAULT '1',
`featured` tinyint(3) unsigned NOT NULL DEFAULT '0',
`now_playing` tinyint(3) unsigned NOT NULL DEFAULT '0',
`created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`updated_at` timestamp NULL DEFAULT NULL,
`temp_id` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`language` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`country` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`original_title` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`affiliate_link` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`custom_field` text COLLATE utf8_unicode_ci,
PRIMARY KEY (`id`),
UNIQUE KEY `titles_imdb_id_unique` (`imdb_id`),
UNIQUE KEY `titles_tmdb_id_type_unique` (`tmdb_id`,`type`),
KEY `titles_mc_num_of_votes_index` (`mc_num_of_votes`),
KEY `titles_created_at_index` (`created_at`),
KEY `titles_release_date_index` (`release_date`),
KEY `titles_title_index` (`title`),
KEY `titles_mc_user_score_index` (`mc_user_score`),
KEY `titles_tmdb_popularity_index` (`tmdb_popularity`),
KEY `titles_temp_id_index` (`temp_id`),
KEY `titles_tmdb_rating_index` (`tmdb_rating`)
) ENGINE=InnoDB AUTO_INCREMENT=18712721 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci
EXPLAIN select * 来自 titles 其中 titles.type = 'movie'
order by tmdb_rating desc limit 100 offset 86500;
+------+-------------+--------+------+---------------+------+---------+------+--------+-----------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+------+-------------+--------+------+---------------+------+---------+------+--------+-----------------------------+
| 1 | SIMPLE | titles | ALL | NULL | NULL | NULL | NULL | 311859 | Using where; Using filesort |
+------+-------------+--------+------+---------------+------+---------+------+--------+-----------------------------+
1 row in set (0.01 sec)
my.cnf 设置：
default-storage-engine = InnoDB
symbolic-links=0
skip-external-locking
max_allowed_packet = 16M
table_open_cache = 5000
query_cache_size = 0
query_cache_type = 0
thread_cache_size = 4
tmp_table_size = 256M
max_heap_table_size = 256M
performance_schema = ON
key_buffer_size = 140k
sort_buffer_size = 256K
read_buffer_size = 128K
read_rnd_buffer_size = 256k
myisam_sort_buffer_size = 140k
join_buffer_size = 2M
innodb_file_per_table
innodb_buffer_pool_size = 512M
innodb_log_file_size = 200M
innodb_buffer_pool_instances = 1
innodb_write_io_threads = 4
innodb_read_io_threads = 4
innodb_thread_concurrency = 4
innodb_flush_method = O_DIRECT
innodb_log_buffer_size = 32M
innodb_io_capacity = 1000
innodb_io_capacity_max = 3000
sync_binlog = 1
max_connections=100
max_user_connections=100
wait_timeout=10
interactive_timeout=30
long_query_time=5
slow-query-log =1
slow-query-log-file = /var/log/mysql/mysql-slow.log
内存使用情况：
Private + Shared = RAM used Program
224.0 KiB + 26.5 KiB = 250.5 KiB agetty (2)
248.0 KiB + 41.0 KiB = 289.0 KiB sftp-server
180.0 KiB + 124.0 KiB = 304.0 KiB anvil
404.0 KiB + 31.5 KiB = 435.5 KiB vsftpd
392.0 KiB + 104.5 KiB = 496.5 KiB dovecot
564.0 KiB + 39.5 KiB = 603.5 KiB memcached
484.0 KiB + 122.0 KiB = 606.0 KiB log
828.0 KiB + 44.0 KiB = 872.0 KiB systemd-udevd
968.0 KiB + 42.0 KiB = 1.0 MiB ntpd
732.0 KiB + 307.0 KiB = 1.0 MiB systemd-logind
684.0 KiB + 355.0 KiB = 1.0 MiB sh (8)
340.0 KiB + 754.0 KiB = 1.1 MiB vesta-nginx (2)
1.0 MiB + 58.5 KiB = 1.1 MiB dbus-daemon
880.0 KiB + 250.5 KiB = 1.1 MiB auth
760.0 KiB + 496.0 KiB = 1.2 MiB flock (6)
1.2 MiB + 244.0 KiB = 1.4 MiB config
1.7 MiB + 205.5 KiB = 1.9 MiB systemd-journald
1.9 MiB + 47.0 KiB = 1.9 MiB rsyslogd
2.1 MiB + 103.0 KiB = 2.2 MiB exim4
2.5 MiB + 76.0 KiB = 2.6 MiB bash
2.5 MiB + 1.3 MiB = 3.8 MiB cron (9)
2.2 MiB + 2.1 MiB = 4.3 MiB sshd (4)
2.2 MiB + 2.1 MiB = 4.4 MiB nginx (3)
500.0 KiB + 4.8 MiB = 5.2 MiB vesta-php (3)
4.3 MiB + 3.7 MiB = 7.9 MiB systemd (5)
15.2 MiB + 109.5 KiB = 15.3 MiB fail2ban-server
67.3 MiB + 15.4 MiB = 82.6 MiB php7.0 (8)
100.9 MiB + 67.2 MiB = 168.1 MiB apache2 (12)
758.7 MiB + 156.0 KiB = 758.9 MiB mysqld
TOP 命令：
top - 14:10:43 up 7 days, 23:12, 1 user, load average: 0.79, 0.91, 0.69
Tasks: 145 total, 4 running, 141 sleeping, 0 stopped, 0 zombie
%Cpu(s): 19.1 us, 6.0 sy, 0.0 ni, 71.9 id, 2.7 wa, 0.0 hi, 0.3 si, 0.0 st
KiB Mem : 2052588 total, 501496 free, 1085916 used, 465176 buff/cache
KiB Swap: 0 total, 0 free, 0 used. 735980 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
23688 mysql 20 0 1211616 770288 0 S 7.3 37.5 543:04.35 mysqld
29889 admin 20 0 539584 53996 38624 R 3.7 2.6 0:00.74 apache2
27140 www-data 20 0 537900 64576 50864 S 3.0 3.1 0:10.99 apache2
29901 admin 20 0 539484 53356 38100 S 2.3 2.6 0:00.71 apache2
29972 admin 20 0 538404 46336 32220 S 2.3 2.3 0:00.24 apache2
29297 admin 20 0 539572 64000 48648 S 2.0 3.1 0:02.00 apache2
30084 www-data 20 0 536388 43876 31700 S 1.3 2.1 0:00.24 apache2
30063 admin 20 0 392344 34440 21948 S 1.0 1.7 0:00.54 php
30042 admin 20 0 311432 30956 21628 S 0.7 1.5 0:00.10 php
30347 root 20 0 44888 3616 3016 R 0.7 0.2 0:00.04 top
7 root 20 0 0 0 0 R 0.3 0.0 8:52.43 rcu_sched
4834 root 20 0 0 0 0 S 0.3 0.0 0:01.46 kworker/u2:2
23741 memcache 20 0 335680 424 0 S 0.3 0.0 2:41.11 memcached
29002 www-data 20 0 537740 70296 56792 S 0.3 3.4 0:03.03 apache2
29279 www-data 20 0 537504 59164 45840 S 0.3 2.9 0:01.75 apache2
29709 root 20 0 0 0 0 S 0.3 0.0 0:00.07 kworker/0:0
1 root 20 0 204556 4732 3076 S 0.0 0.2 0:21.00 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.01 kthreadd
3 root 20 0 0 0 0 R 0.0 0.0 8:12.40 ksoftirqd/0
另一个慢查询示例：
# Query_time: 21.742335 Lock_time: 0.000042 Rows_sent: 0 Rows_examined: 354027
# Rows_affected: 0
SET timestamp=1560293586;
select * from `titles`
where `titles`.`type` = 'movie'
and ( select count(*)
from `actors`
inner join `actors_titles` on `actors`.`id` = `actors_titles`.`actor_id`
where `actors_titles`.`title_id` = `titles`.`id`
and `name` like 'teren'
) >= 1
order by `mc_num_of_votes` asc
limit 100 offset 0;
呃：limit 100 offset 86500
不要那样做分页。相反 "remember where you left off"。这样做的缺点是没有提供 "jump to page 864"，但谁来提供。谁Next-next-next... 865次？
关于这个常见问题的进一步讨论：http://mysql.rjweb.org/doc.php/pagination
并且更详细地讨论了 "left off" 解决方案。
另一个潜在问题：order by tmdb_rating desc -- 也许多个标题具有相同的 "rating"？如果是这样，您希望以什么顺序列出标题？简单的答案是指定一些明确的（但有些武断的）顺序：order by tmdb_rating desc, id desc.
记住你在化合物中离开的地方 order-by 更复杂，但有可能。
其他说明：
WHERE type=... ORDER BY rating可以受益于"composite"INDEX(type, rating)，顺序为
3 个唯一键听起来不对。
2 提取的 TEXT 列会影响性能。不要做 SELECT * 除非你真的需要所有的列。
tmp_table_size = 256M 和 max_heap_table_size = 256M 对于 2GB 的 RAM 来说是危险的。将它们缩小到只有 1% 的 RAM。
而不是( SELECT COUNT(*) FROM...) >=1，做EXISTS ( SELECT 1 FROM ...)
我的 php 应用程序使用 laravel 4.1.31。对于数据库查询，它通过ajax使用knockout js库。当数据库变大时，ajax加载成为一个问题，因为加载时间太长，有时会中途停止。我不熟悉这些库，所以我无法进行任何应用程序级别的优化。
我希望我仍然可以对数据库查询进行优化，并将每个查询控制在 5 秒以内。
以下是我可以分享的一些信息：
内存：2GB 1core Debian 9。 单个 Innodb 数据库。
慢查询日志：
# Time: 190611 7:49:08
# User@Host: user[user] @ localhost []
# Thread_id: 690728 Schema: user QC_hit: No
# Query_time: 9.343611 Lock_time: 0.000030 Rows_sent: 100 Rows_examined: 440481
# Rows_affected: 0
use user;
SET timestamp=1560239348;
select * from `titles` where `titles`.`type` = 'movie'
order by `tmdb_rating` desc limit 100 offset 86500;
显示创建 TABLE 个标题；
CREATE TABLE `titles` (
`id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
`title` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`type` enum('movie','series') COLLATE utf8_unicode_ci DEFAULT NULL,
`imdb_rating` varchar(10) COLLATE utf8_unicode_ci DEFAULT NULL,
`tmdb_rating` varchar(10) COLLATE utf8_unicode_ci DEFAULT NULL,
`mc_user_score` varchar(10) COLLATE utf8_unicode_ci DEFAULT NULL,
`mc_critic_score` smallint(5) unsigned DEFAULT NULL,
`mc_num_of_votes` int(10) unsigned DEFAULT NULL,
`imdb_votes_num` bigint(20) unsigned DEFAULT NULL,
`release_date` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`year` smallint(5) unsigned DEFAULT NULL,
`plot` text COLLATE utf8_unicode_ci,
`genre` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`tagline` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`poster` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`background` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`awards` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`runtime` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`trailer` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`budget` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`revenue` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`views` bigint(20) NOT NULL DEFAULT '1',
`tmdb_popularity` float(50,2) unsigned DEFAULT NULL,
`imdb_id` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`tmdb_id` bigint(20) unsigned DEFAULT NULL,
`season_number` tinyint(3) unsigned DEFAULT NULL,
`fully_scraped` tinyint(3) unsigned NOT NULL DEFAULT '0',
`allow_update` tinyint(3) unsigned NOT NULL DEFAULT '1',
`featured` tinyint(3) unsigned NOT NULL DEFAULT '0',
`now_playing` tinyint(3) unsigned NOT NULL DEFAULT '0',
`created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`updated_at` timestamp NULL DEFAULT NULL,
`temp_id` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`language` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`country` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`original_title` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`affiliate_link` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL,
`custom_field` text COLLATE utf8_unicode_ci,
PRIMARY KEY (`id`),
UNIQUE KEY `titles_imdb_id_unique` (`imdb_id`),
UNIQUE KEY `titles_tmdb_id_type_unique` (`tmdb_id`,`type`),
KEY `titles_mc_num_of_votes_index` (`mc_num_of_votes`),
KEY `titles_created_at_index` (`created_at`),
KEY `titles_release_date_index` (`release_date`),
KEY `titles_title_index` (`title`),
KEY `titles_mc_user_score_index` (`mc_user_score`),
KEY `titles_tmdb_popularity_index` (`tmdb_popularity`),
KEY `titles_temp_id_index` (`temp_id`),
KEY `titles_tmdb_rating_index` (`tmdb_rating`)
) ENGINE=InnoDB AUTO_INCREMENT=18712721 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci
EXPLAIN select * 来自 titles 其中 titles.type = 'movie'
order by tmdb_rating desc limit 100 offset 86500;
+------+-------------+--------+------+---------------+------+---------+------+--------+-----------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+------+-------------+--------+------+---------------+------+---------+------+--------+-----------------------------+
| 1 | SIMPLE | titles | ALL | NULL | NULL | NULL | NULL | 311859 | Using where; Using filesort |
+------+-------------+--------+------+---------------+------+---------+------+--------+-----------------------------+
1 row in set (0.01 sec)
my.cnf 设置：
default-storage-engine = InnoDB
symbolic-links=0
skip-external-locking
max_allowed_packet = 16M
table_open_cache = 5000
query_cache_size = 0
query_cache_type = 0
thread_cache_size = 4
tmp_table_size = 256M
max_heap_table_size = 256M
performance_schema = ON
key_buffer_size = 140k
sort_buffer_size = 256K
read_buffer_size = 128K
read_rnd_buffer_size = 256k
myisam_sort_buffer_size = 140k
join_buffer_size = 2M
innodb_file_per_table
innodb_buffer_pool_size = 512M
innodb_log_file_size = 200M
innodb_buffer_pool_instances = 1
innodb_write_io_threads = 4
innodb_read_io_threads = 4
innodb_thread_concurrency = 4
innodb_flush_method = O_DIRECT
innodb_log_buffer_size = 32M
innodb_io_capacity = 1000
innodb_io_capacity_max = 3000
sync_binlog = 1
max_connections=100
max_user_connections=100
wait_timeout=10
interactive_timeout=30
long_query_time=5
slow-query-log =1
slow-query-log-file = /var/log/mysql/mysql-slow.log
内存使用情况：
Private + Shared = RAM used Program
224.0 KiB + 26.5 KiB = 250.5 KiB agetty (2)
248.0 KiB + 41.0 KiB = 289.0 KiB sftp-server
180.0 KiB + 124.0 KiB = 304.0 KiB anvil
404.0 KiB + 31.5 KiB = 435.5 KiB vsftpd
392.0 KiB + 104.5 KiB = 496.5 KiB dovecot
564.0 KiB + 39.5 KiB = 603.5 KiB memcached
484.0 KiB + 122.0 KiB = 606.0 KiB log
828.0 KiB + 44.0 KiB = 872.0 KiB systemd-udevd
968.0 KiB + 42.0 KiB = 1.0 MiB ntpd
732.0 KiB + 307.0 KiB = 1.0 MiB systemd-logind
684.0 KiB + 355.0 KiB = 1.0 MiB sh (8)
340.0 KiB + 754.0 KiB = 1.1 MiB vesta-nginx (2)
1.0 MiB + 58.5 KiB = 1.1 MiB dbus-daemon
880.0 KiB + 250.5 KiB = 1.1 MiB auth
760.0 KiB + 496.0 KiB = 1.2 MiB flock (6)
1.2 MiB + 244.0 KiB = 1.4 MiB config
1.7 MiB + 205.5 KiB = 1.9 MiB systemd-journald
1.9 MiB + 47.0 KiB = 1.9 MiB rsyslogd
2.1 MiB + 103.0 KiB = 2.2 MiB exim4
2.5 MiB + 76.0 KiB = 2.6 MiB bash
2.5 MiB + 1.3 MiB = 3.8 MiB cron (9)
2.2 MiB + 2.1 MiB = 4.3 MiB sshd (4)
2.2 MiB + 2.1 MiB = 4.4 MiB nginx (3)
500.0 KiB + 4.8 MiB = 5.2 MiB vesta-php (3)
4.3 MiB + 3.7 MiB = 7.9 MiB systemd (5)
15.2 MiB + 109.5 KiB = 15.3 MiB fail2ban-server
67.3 MiB + 15.4 MiB = 82.6 MiB php7.0 (8)
100.9 MiB + 67.2 MiB = 168.1 MiB apache2 (12)
758.7 MiB + 156.0 KiB = 758.9 MiB mysqld
TOP 命令：
top - 14:10:43 up 7 days, 23:12, 1 user, load average: 0.79, 0.91, 0.69
Tasks: 145 total, 4 running, 141 sleeping, 0 stopped, 0 zombie
%Cpu(s): 19.1 us, 6.0 sy, 0.0 ni, 71.9 id, 2.7 wa, 0.0 hi, 0.3 si, 0.0 st
KiB Mem : 2052588 total, 501496 free, 1085916 used, 465176 buff/cache
KiB Swap: 0 total, 0 free, 0 used. 735980 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
23688 mysql 20 0 1211616 770288 0 S 7.3 37.5 543:04.35 mysqld
29889 admin 20 0 539584 53996 38624 R 3.7 2.6 0:00.74 apache2
27140 www-data 20 0 537900 64576 50864 S 3.0 3.1 0:10.99 apache2
29901 admin 20 0 539484 53356 38100 S 2.3 2.6 0:00.71 apache2
29972 admin 20 0 538404 46336 32220 S 2.3 2.3 0:00.24 apache2
29297 admin 20 0 539572 64000 48648 S 2.0 3.1 0:02.00 apache2
30084 www-data 20 0 536388 43876 31700 S 1.3 2.1 0:00.24 apache2
30063 admin 20 0 392344 34440 21948 S 1.0 1.7 0:00.54 php
30042 admin 20 0 311432 30956 21628 S 0.7 1.5 0:00.10 php
30347 root 20 0 44888 3616 3016 R 0.7 0.2 0:00.04 top
7 root 20 0 0 0 0 R 0.3 0.0 8:52.43 rcu_sched
4834 root 20 0 0 0 0 S 0.3 0.0 0:01.46 kworker/u2:2
23741 memcache 20 0 335680 424 0 S 0.3 0.0 2:41.11 memcached
29002 www-data 20 0 537740 70296 56792 S 0.3 3.4 0:03.03 apache2
29279 www-data 20 0 537504 59164 45840 S 0.3 2.9 0:01.75 apache2
29709 root 20 0 0 0 0 S 0.3 0.0 0:00.07 kworker/0:0
1 root 20 0 204556 4732 3076 S 0.0 0.2 0:21.00 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.01 kthreadd
3 root 20 0 0 0 0 R 0.0 0.0 8:12.40 ksoftirqd/0
另一个慢查询示例：
# Query_time: 21.742335 Lock_time: 0.000042 Rows_sent: 0 Rows_examined: 354027
# Rows_affected: 0
SET timestamp=1560293586;
select * from `titles`
where `titles`.`type` = 'movie'
and ( select count(*)
from `actors`
inner join `actors_titles` on `actors`.`id` = `actors_titles`.`actor_id`
where `actors_titles`.`title_id` = `titles`.`id`
and `name` like 'teren'
) >= 1
order by `mc_num_of_votes` asc
limit 100 offset 0;
呃：limit 100 offset 86500
不要那样做分页。相反 "remember where you left off"。这样做的缺点是没有提供 "jump to page 864"，但谁来提供。谁Next-next-next... 865次？
关于这个常见问题的进一步讨论：http://mysql.rjweb.org/doc.php/pagination
并且更详细地讨论了 "left off" 解决方案。
另一个潜在问题：order by tmdb_rating desc -- 也许多个标题具有相同的 "rating"？如果是这样，您希望以什么顺序列出标题？简单的答案是指定一些明确的（但有些武断的）顺序：order by tmdb_rating desc, id desc.
记住你在化合物中离开的地方 order-by 更复杂，但有可能。
其他说明：
WHERE type=... ORDER BY rating可以受益于"composite"INDEX(type, rating)，顺序为3 个唯一键听起来不对。
2 提取的 TEXT 列会影响性能。不要做
SELECT *除非你真的需要所有的列。tmp_table_size = 256M和max_heap_table_size = 256M对于 2GB 的 RAM 来说是危险的。将它们缩小到只有 1% 的 RAM。而不是
( SELECT COUNT(*) FROM...) >=1，做EXISTS ( SELECT 1 FROM ...)