MySQL: 慢 select 没有 where 和 joins

Question

我有以下 table:

| ticket | CREATE TABLE `ticket` (
  `ticket_id` bigint(20) NOT NULL AUTO_INCREMENT,
  `client_id` binary(16) NOT NULL,
  `owner_id` binary(16) DEFAULT NULL,
  `requester_id` binary(16) NOT NULL,
  `ticket_type` varchar(15) COLLATE utf8mb4_unicode_ci NOT NULL,
  `status` varchar(18) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `priority` varchar(5) COLLATE utf8mb4_unicode_ci NOT NULL,
  `subject` varchar(255) COLLATE utf8mb4_unicode_ci NOT NULL,
  `created` datetime(3) NOT NULL,
  `updated` datetime(3) NOT NULL,
  `eta` datetime(3) NOT NULL,
  `version` bigint(20) NOT NULL DEFAULT '0',
  `office_id` binary(16) DEFAULT NULL,
  `department_id` binary(16) DEFAULT NULL,
  `requester` varchar(255) COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT '',
  `requester_type` varchar(255) COLLATE utf8mb4_unicode_ci NOT NULL DEFAULT 'IPDEPLOY',
  `assignment_group_id` binary(16) DEFAULT NULL,
  PRIMARY KEY (`ticket_id`),
  KEY `idx_ticket_office_id` (`office_id`),
  KEY `idx_ticket_department_id` (`department_id`),
  KEY `idx_ticket_client_id` (`client_id`)
) ENGINE=InnoDB AUTO_INCREMENT=3116172 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci ROW_FORMAT=DYNAMIC ENCRYPTION='Y';

mysql> select count(*) from ticket;
+----------+
| count(*) |
+----------+
|  1190895 |
+----------+
mysql> SHOW TABLE STATUS WHERE name LIKE 'ticket' \G
*************************** 1. row ***************************
           Name: ticket
         Engine: InnoDB
        Version: 10
     Row_format: Dynamic
           Rows: 1101291
 Avg_row_length: 375
    Data_length: 413089792
Max_data_length: 0
   Index_length: 153468928
      Data_free: 6291456
 Auto_increment: 3121563
    Create_time: 2022-05-18 09:51:06
    Update_time: 2022-05-19 12:06:18
     Check_time: NULL
      Collation: utf8mb4_unicode_ci
       Checksum: NULL
 Create_options: row_format=DYNAMIC ENCRYPTION="Y"
        Comment:
1 row in set (0.00 sec)

简单的查询间歇性地花费大量时间（大约 30% 的此类查询花费超过 500 毫秒（有些长达 3 秒））：

mysql> select * from ticket limit 20, 20;
...
20 rows in set (0.77 sec)

分析时，所有时间都花在启动阶段：

mysql> SELECT * FROM INFORMATION_SCHEMA.PROFILING WHERE QUERY_ID=37 order by duration DESC limit 2 \G
*************************** 1. row ***************************
           QUERY_ID: 37
                SEQ: 2
              STATE: starting
           DURATION: 0.760068
           CPU_USER: NULL
         CPU_SYSTEM: NULL
  CONTEXT_VOLUNTARY: NULL
CONTEXT_INVOLUNTARY: NULL
       BLOCK_OPS_IN: NULL
      BLOCK_OPS_OUT: NULL
      MESSAGES_SENT: NULL
  MESSAGES_RECEIVED: NULL
  PAGE_FAULTS_MAJOR: NULL
  PAGE_FAULTS_MINOR: NULL
              SWAPS: NULL
    SOURCE_FUNCTION: NULL
        SOURCE_FILE: NULL
        SOURCE_LINE: NULL
*************************** 2. row ***************************
           QUERY_ID: 37
                SEQ: 11
              STATE: Sending data
           DURATION: 0.000234
           CPU_USER: NULL
         CPU_SYSTEM: NULL
  CONTEXT_VOLUNTARY: NULL
CONTEXT_INVOLUNTARY: NULL
       BLOCK_OPS_IN: NULL
      BLOCK_OPS_OUT: NULL
      MESSAGES_SENT: NULL
  MESSAGES_RECEIVED: NULL
  PAGE_FAULTS_MAJOR: NULL
  PAGE_FAULTS_MINOR: NULL
              SWAPS: NULL
    SOURCE_FUNCTION: exec
        SOURCE_FILE: sql_executor.cc
        SOURCE_LINE: 195

MySQL手册对起始状态没有说太多：“语句执行开始时的第一阶段。”。我怎样才能知道 MySQL 在这种状态下实际上在做什么？这种行为的原因可能是什么？

MySQL CentOS Linux 5.7.27-30-57-log 运行 Linux Azure 容器内的 7.7.1908 版。根本没有加载数据库。

innodb_buffer_pool_size设置为12G

IOwait 和普罗米修斯指标：

Answer 1

最后我们通过将 wsrep_sync_wait 设置为 0 来解决这个问题。

MySQL: 慢 select 没有 where 和 joins

MySQL: slow select without where and joins

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