读取查询锁定在表上插入新记录时出现错误 - 超出锁定等待超时；尝试重新启动交易

问题描述 投票：0回答：1

我有一个存储过程，每隔一小时运行一次，以生成服务中发生的事务的摘要。存储过程从名为 transaction_log 的表中读取数据，并填充（插入或更新行）另一个名为 transaction_log_summary 的表。表之间在约束级别上没有连接，即没有外键引用等。但是由于某种原因，当存储过程在一天中第一次运行并且同时在 transaction_log 上执行了新的插入查询时一次，插入语句失败并超出锁定等待超时；尝试重新启动事务错误。这里使用的默认隔离级别是REPEATABLE READ (innoDB)。读操作如何锁定表以防止插入新行？

下面分享存储过程和相关代码。

用于更新汇总表中条目的函数

DELIMITER //
CREATE PROCEDURE func_update_summary(IN date_param DATE, IN last_summary_index BIGINT)
BEGIN
    -- Update the summary for the input date with logs having newer ids 
        UPDATE transaction_log_summary tls
        JOIN (
            SELECT 
                DATE(created_at) AS date,
                SUM(CASE WHEN channel = 'NATS' THEN 1 ELSE 0 END) AS channel_NATS,
                SUM(CASE WHEN channel = 'SQS' THEN 1 ELSE 0 END) AS channel_SQS,
                SUM(CASE WHEN channel = 'API' THEN 1 ELSE 0 END) AS channel_API,
                SUM(CASE WHEN status = 'SUCCESS' THEN 1 ELSE 0 END) AS status_SUCCESS,
                SUM(CASE WHEN status = 'FAILURE' THEN 1 ELSE 0 END) AS status_FAILURE,
                SUM(CASE WHEN status = 'SKIPPED' THEN 1 ELSE 0 END) AS status_SKIPPED,
                MAX(id) AS last_transaction_log_index
            FROM 
                transaction_log
            WHERE
                DATE(created_at) = date_param
                AND id > last_summary_index
            GROUP BY 
                DATE(created_at)
        ) AS temp ON tls.date = temp.date
        SET 
            tls.channel_NATS = tls.channel_NATS + temp.channel_NATS,
            tls.channel_SQS = tls.channel_SQS + temp.channel_SQS,
            tls.channel_API = tls.channel_API + temp.channel_API,
            tls.status_SUCCESS = tls.status_SUCCESS + temp.status_SUCCESS,
            tls.status_FAILURE = tls.status_FAILURE + temp.status_FAILURE,
            tls.status_SKIPPED = tls.status_SKIPPED + temp.status_SKIPPED,
            tls.last_transaction_log_index = temp.last_transaction_log_index
        WHERE
            tls.date = date_param;
END//

DELIMITER ;

使用上述函数执行日期检查并更新值的存储过程

DELIMITER //

CREATE PROCEDURE proc_update_transaction_log_summary()
BEGIN
    DECLARE present_date DATE;
    DECLARE last_summary_date DATE;
    DECLARE last_summary_index BIGINT;
    DECLARE last_log_index BIGINT;
    DECLARE has_records INT;

    DECLARE error_code INT;
    DECLARE error_msg VARCHAR(255);

    DECLARE lock_acquired INT DEFAULT 0;

    -- Try to acquire the named lock immediately
    SET lock_acquired = GET_LOCK('update_summary_lock', 0); -- 0 means try to acquire immediately
    
    IF lock_acquired = 1 THEN
        BEGIN
            DECLARE EXIT HANDLER FOR SQLEXCEPTION
            BEGIN
                GET DIAGNOSTICS CONDITION 1 error_code = MYSQL_ERRNO, error_msg = MESSAGE_TEXT;
                ROLLBACK;
                SELECT CONCAT('Error ', error_code, ': ', error_msg);
                DO RELEASE_LOCK('update_summary_lock');
            END;

            START TRANSACTION;
            
            SET present_date = CURDATE();
            
            -- Get the last index and date from transaction_log_summary table
            SELECT last_transaction_log_index, date INTO last_summary_index, last_summary_date
            FROM transaction_log_summary
            ORDER BY date DESC
            LIMIT 1;

            -- If last summary date is less than current date, update the summary
            IF last_summary_date < present_date THEN
                BEGIN
                    -- Get the last index from the transaction log for the last_summary_date
                    SELECT MAX(id) INTO last_log_index FROM transaction_log 
                    WHERE DATE(created_at) = last_summary_date;

                    IF last_log_index > last_summary_index THEN
                        CALL func_update_summary(last_summary_date, last_summary_index);
                    END IF;
                    
                    -- Check if there are records for the present date
                    SELECT EXISTS ( SELECT 1 FROM transaction_log WHERE DATE(created_at) =
                    CURRENT_DATE LIMIT 1) INTO has_records;

                    IF has_records THEN
                        
                        -- Insert new record in the summary table for the current date
                        INSERT INTO transaction_log_summary (date, channel_NATS, channel_SQS, channel_API, status_SUCCESS, status_FAILURE, status_SKIPPED, last_transaction_log_index)
                        SELECT present_date,
                            SUM(CASE WHEN channel = 'NATS' THEN 1 ELSE 0 END) AS channel_NATS,
                            SUM(CASE WHEN channel = 'SQS' THEN 1 ELSE 0 END) AS channel_SQS,
                            SUM(CASE WHEN channel = 'API' THEN 1 ELSE 0 END) AS channel_API,
                            SUM(CASE WHEN status = 'SUCCESS' THEN 1 ELSE 0 END) AS status_SUCCESS,
                            SUM(CASE WHEN status = 'FAILURE' THEN 1 ELSE 0 END) AS status_FAILURE,
                            SUM(CASE WHEN status = 'SKIPPED' THEN 1 ELSE 0 END) AS status_SKIPPED,
                            MAX(id) AS last_transaction_log_index
                        FROM transaction_log
                        WHERE DATE(created_at) = present_date;

                    ELSE
                        -- Insert new record in the summary table for the present date with last index from previous day
                        INSERT INTO transaction_log_summary (date,  last_transaction_log_index)
                        SELECT present_date, MAX(id) AS last_transaction_log_index
                        FROM transaction_log;

                    END IF;
                END;
            ELSE
                BEGIN
                    -- Get the last index from the transaction log for the last_summary_date
                    SELECT MAX(id) INTO last_log_index FROM transaction_log 
                    WHERE DATE(created_at) = present_date;
                    
                    -- Check if there are new entries in the log table
                    IF last_log_index > last_summary_index THEN
                        CALL func_update_summary(present_date, last_summary_index);
                    END IF;
                END;
            END IF;
            
            COMMIT;
            SELECT ''; -- empty msg utilised by app layer to identify successful end of execution
            DO RELEASE_LOCK('update_summary_lock');
        END;
    END IF;

END//

DELIMITER ;

事件计划每隔一小时执行一次该过程

DELIMITER //
CREATE EVENT job_update_transaction_log_summary
ON SCHEDULE
    EVERY 1 HOUR
DO
BEGIN
    CALL proc_update_transaction_log_summary();
END//
DELIMITER ;

此外，观察到在存储过程隔离级别更新为 READ COMMITTED 的部署环境之一中，我们没有遇到此问题。 即在存储过程中，在事务开始之前，我们设置隔离级别。

SET SESSION TRANSACTION ISOLATION LEVEL READ COMMITTED;

但是读操作怎么会导致这个问题呢？存储过程的不同隔离级别的设置是否真正解决了问题，还是我们会在不同的用例中遇到该问题？

mysql stored-procedures innodb isolation-level transaction-isolation
1个回答
0
投票

作为 DML 语句 (

INSERT
/
UPDATE
/
DELETE
) 一部分执行的任何读查询都隐式是锁定读。

https://dev.mysql.com/doc/refman/8.0/en/innodb-locks-set.html 说：

INSERT INTO T SELECT ... FROM S WHERE ...
设置独占索引 插入 T 的每一行上的记录锁（没有间隙锁）。如果 事务隔离级别是 READ COMMITTED，InnoDB 进行搜索 在 S 上作为一致读取（无锁）。否则，InnoDB 设置共享 来自 S 的行上的下一个键锁。InnoDB 必须在后者中设置锁 案例：在使用基于语句的二进制日志进行前滚恢复期间， 每个 SQL 语句必须以完全相同的方式执行 原来已经完成了。

CREATE TABLE ... SELECT ...
使用共享的下一个键执行 SELECT 锁定或作为一致读取，如
INSERT ... SELECT
。

当

SELECT
用于构造
REPLACE INTO t SELECT ... FROM s WHERE ...
或
UPDATE t ... WHERE col IN (SELECT ... FROM s ...)
时， InnoDB 对表 s 中的行设置共享下一键锁。

该手册页没有明确列出这些情况，但这也会影响以下情况：

SELECT ... INTO @var;

SET @var = (SELECT ...);

UPDATE ... JOIN (SELECT...)

Foreign key checks

SELECT inside a DML trigger
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