select语句可以触发mysql中表的死锁吗？

Question

• 下面的 SQL 在 MySQL 存储过程中。
• cron 作业每天在午夜运行一次以使用结果填充报告表的过程。
• 此过程大约需要 2 分钟才能运行。
• 请注意，table1 拥有数百万条记录。
• 我让它在午夜运行，因为白天有 INSERT/UPDATE 交易，但不幸的是晚上也有一些交易。
• 当此过程运行时，如果有其他事务正在运行，则会在 table1 上发生死锁错误。

我的问题是

1. 为什么SELECT 语句导致table1 死锁？
2. 在这种情况下如何避免死锁？

DROP report;

CREATE TABLE IF NOT EXISTS report AS (
    
    SELECT
        DISTINCT
        
        companies.id company_id,

        (
            SELECT 
                SUM(`message_count`) single_phone
            FROM
                `table1`
            WHERE
                `table1`.`company_id` = companies.id
                AND
                `status` != 'error'
        ) AS single_phone,

        (
            SELECT 
                SUM(`message_count`)
            FROM
                `table1`
            WHERE
                `table1`.`company_id` = companies.id
                AND
                `status` != 'not error'
        ) AS log,

        (
            SELECT 
                SUM(`message_count`)
            FROM
                `table1`
            WHERE
                `table1`.`company_id` = companies.id
                AND
                `status` != 'error'
        ) AS log_monthly,

        (
            SELECT 
                SUM(`number_of_sms`) AS aggregate
            FROM
                `messages`
            WHERE
                `messages`.`company_id` = companies.id
        ) AS p_monthly
    FROM
        companies
        INNER JOIN company_users ON companies.id = company_users.company_id
    WHERE
        company_users.confirmed = 1
        AND
        company_users.deleted_at IS NULL
);

Answer 1

非常感谢您的帮助，但我找到了问题所在。是的，这个过程会导致表上的死锁，但问题的实际原因是我已将 ->everyMinute() 放在我的 laravel 内核中以进行计划运行。并且还有一个由另一个开发人员配置的 cron 作业，每分钟运行一次。这些将每分钟运行一次，这是死锁问题的真正原因。我已将我的内核计划更改为 ->dailyAt('02:00');现在问题解决了。

Answer 2

您的字段级查询应在 from 子句中执行一次，以便为每个公司 ID 完成一次预聚合并左连接，以防给定公司在给定类别中可能没有合格记录。此外，您获取 Single_Phone 的查询与您的“log_monthly”相同，但没有条件显示 打破或过滤活动日期以过滤出单个月与所有内容的总和。因此，我添加了一个 where 子句进行过滤，但仅在存在此类日期时才 GUESSING。

此查询可能会大大提高您的性能。通过将每个公司 ID 的基于 COLUMN 的查询通过左连接移动到其自己的子查询中，这些查询将被 summed() 并按公司 ONCE 分组，然后是最终结果的 JOIN。使用 COALESCE()，所以如果不存在这样的计数，则返回的值将是 0 而不是 null

DROP report;

CREATE TABLE IF NOT EXISTS report AS (
      SELECT
            c.id company_id,
            coalesce( PhoneSum.Msgs, 0 ) as Single_Phone,
            coalesce( PhoneLog.Msgs, 0 ) as Log,
            coalesce( MonthLog.Msgs, 0 ) as Log_Monthly,
            coalesce( SMSSummary.Aggregate, 0 ) as p_monthly
        from
            -- this will declare an in-line variable if you do need to filter by a month as a couple of your
            -- column result names infer, but have no other indicator of filtering by a given month.
            ( select @yesterday := date_sub( date(curdate()), interval -1 day ),
                    @beginOfThatMonth := date_sub( @yesterday, interval dayOfMonth( @yesterday ) -1 day ) sqlvars,
            companies c
                INNER JOIN company_users cu
                    ON m.company.id = cu.company_id
                    AND cu.confirmed = 1
                    AND cu.deleted_at IS NULL
    
                LEFT JOIN
                ( SELECT 
                        t.company_id,
                        SUM( t.message_count ) Msgs
                    FROM
                        table1 t
                            INNER JOIN company_users cu
                                ON t.company.id = cu.company_id
                                AND cu.confirmed = 1
                                AND cu.deleted_at IS NULL
                    where
                        t.status != 'error'
                    GROUP BY
                        t.company_id ) AS PhoneSum,
                    on c.id = PhoneSum.company_id
    
                LEFT JOIN
                ( SELECT 
                        t.company_id,
                        SUM( t.message_count ) Msgs
                    FROM
                        table1 t
                            INNER JOIN company_users cu
                                ON t.company.id = cu.company_id
                                AND cu.confirmed = 1
                                AND cu.deleted_at IS NULL
                    where
                        t.status != 'not error'
                    GROUP BY
                        t.company_id ) AS PhoneLog,
                    on c.id = PhoneLog.company_id
    
                LEFT JOIN
                ( SELECT 
                        t.company_id,
                        SUM( t.message_count ) Msgs
                    FROM
                        table1 t
                            INNER JOIN company_users cu
                                ON t.company.id = cu.company_id
                                AND cu.confirmed = 1
                                AND cu.deleted_at IS NULL
                    where
                            t.status != 'error'
                        -- this would only get counts of activity for current month currently active
                        -- but since you are running at night, you need the day before current
                        AND t.SomeDateFieldOnTable1 >= @beginOfThatMonth
                    GROUP BY
                        t.company_id ) AS MonthLogMsgs,
                    on c.id = MonthLogMsgs.company_id
    
                LEFT JOIN
                ( SELECT 
                        m.company_id,
                        SUM( m.number_of_sms ) aggregate
                    FROM
                        messages m
                            INNER JOIN company_users cu
                                ON m.company.id = cu.company_id
                                AND cu.confirmed = 1
                                AND cu.deleted_at IS NULL
                    where
                        m.SomeDateFieldOnMessagesTable >= @beginOfThatMonth
                    GROUP BY
                        company_id ) AS SMSSummary,
                    on c.id = SMSSummary.company_id