应该有开发测试相关的兄弟常常发现,某些半夜跑的报表系统,在系统开始时候好好的,但是数据量越来越大的情况下,报表系统会
应该有开发测试相关的兄弟常常发现,某些半夜跑的报表系统,在系统开始时候好好的,但是数据量越来越大的情况下,报表系统会越来越慢。
一般我们可以理解为sql需要优化,存储需要优化等等。
这里,如果我们使用的是Oracle 10G以上版本,就要小心了,有可能是Oracle自己搞的鬼。
Oracle10g增加了一个新的任务,用来自动分析数据库,已增加CBO执行的正确性。这个任务就是GATHER_STATS_JOB,,任务定义周一到周五的半夜执行,和周六日全天执行。
出发点很好,但是,大部分业务晚上常常也要跑大的查询,或者执行计划改变,会引起新的性能问题。这个都是可以预见的。
下面备忘。
查看任务详情:
SELECT owner,job_name,state,last_start_date,last_run_duration,failure_count
FROM dba_scheduler_jobs WHERE job_name = 'GATHER_STATS_JOB';
select PROGRAM_ACTION from dba_scheduler_programs where PROGRAM_NAME = 'GATHER_STATS_PROG';
任务执行历史:
SELECT log_id, job_name, status,
TO_CHAR (log_date, 'DD-MON-YYYY HH24:MI') log_date
FROM dba_scheduler_job_run_details
WHERE job_name = 'GATHER_STATS_JOB';
禁用任务:
在sysdba下执行:
exec DBMS_SCHEDULER.DISABLE('GATHER_STATS_JOB');

MySQLoffersvariousstorageengines,eachsuitedfordifferentusecases:1)InnoDBisidealforapplicationsneedingACIDcomplianceandhighconcurrency,supportingtransactionsandforeignkeys.2)MyISAMisbestforread-heavyworkloads,lackingtransactionsupport.3)Memoryengineis

Common security vulnerabilities in MySQL include SQL injection, weak passwords, improper permission configuration, and unupdated software. 1. SQL injection can be prevented by using preprocessing statements. 2. Weak passwords can be avoided by forcibly using strong password strategies. 3. Improper permission configuration can be resolved through regular review and adjustment of user permissions. 4. Unupdated software can be patched by regularly checking and updating the MySQL version.

Identifying slow queries in MySQL can be achieved by enabling slow query logs and setting thresholds. 1. Enable slow query logs and set thresholds. 2. View and analyze slow query log files, and use tools such as mysqldumpslow or pt-query-digest for in-depth analysis. 3. Optimizing slow queries can be achieved through index optimization, query rewriting and avoiding the use of SELECT*.

To monitor the health and performance of MySQL servers, you should pay attention to system health, performance metrics and query execution. 1) Monitor system health: Use top, htop or SHOWGLOBALSTATUS commands to view CPU, memory, disk I/O and network activities. 2) Track performance indicators: monitor key indicators such as query number per second, average query time and cache hit rate. 3) Ensure query execution optimization: Enable slow query logs, record and optimize queries whose execution time exceeds the set threshold.

The main difference between MySQL and MariaDB is performance, functionality and license: 1. MySQL is developed by Oracle, and MariaDB is its fork. 2. MariaDB may perform better in high load environments. 3.MariaDB provides more storage engines and functions. 4.MySQL adopts a dual license, and MariaDB is completely open source. The existing infrastructure, performance requirements, functional requirements and license costs should be taken into account when choosing.

MySQL uses a GPL license. 1) The GPL license allows the free use, modification and distribution of MySQL, but the modified distribution must comply with GPL. 2) Commercial licenses can avoid public modifications and are suitable for commercial applications that require confidentiality.

The situations when choosing InnoDB instead of MyISAM include: 1) transaction support, 2) high concurrency environment, 3) high data consistency; conversely, the situation when choosing MyISAM includes: 1) mainly read operations, 2) no transaction support is required. InnoDB is suitable for applications that require high data consistency and transaction processing, such as e-commerce platforms, while MyISAM is suitable for read-intensive and transaction-free applications such as blog systems.

In MySQL, the function of foreign keys is to establish the relationship between tables and ensure the consistency and integrity of the data. Foreign keys maintain the effectiveness of data through reference integrity checks and cascading operations. Pay attention to performance optimization and avoid common errors when using them.


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