About me:Oracle ACE pro,optimistic,passionate and harmonious. Focus on ORACLE,MySQL and other database programming,peformance tuning,db design, j2ee,Linux/AIX,Architecture tech,etc
全部博文(191)
发布时间:2023-05-09 23:07:29
DETERMINISTIC不建立索引,缓存无效,执行的时候还是调用函数,DETERMINISTIC+索引才能缓存,执行的时候不再调用函数......【阅读全文】
发布时间:2023-05-09 16:57:39
经常遇到执行计划突变,游标不能共享,需要找到其根本原因,可以查看v$sql_shared_cursor视图,这个视图有64种原因:......【阅读全文】
发布时间:2023-05-09 15:32:41
11g开始的Cardinality Feedback基数反馈(12c叫statistics Feedback)属于CBO优化器自动优化特性,由于表可能缺少统计信息、或收集的统计信息不准确或条件复杂CBO无法估算准确的返回行数导致走错执行计划,因此,引入Cardinality Feedback功能,第一次执行会记录条件实际返回的行数,然后与优化器估算的返回行数对比,如果差别很大,后续执行会用第一次实际返回的行数会修正执行计划。使用了Cardinality Feedback特性的,可以在执行计划NOTES部分看到” cardinality feedback used for this statement”......【阅读全文】
发布时间:2023-05-09 15:25:56
10g正常,升级11g r2后日期转换出错,temp_value_code存多种格式字符串。
正确执行计划LT关联查询先执行,之后与外表关联。
错误执行计划是TASK_SPRING_VALUES先与外表关联然后分组,作为VIEW再与TASK_SPRING_LABEL关联,导致报错。......【阅读全文】
吻的感觉适2025-07-18 23:11
https://txc.qq.com/products/762795/blog/2019636
https://txc.qq.com/products/762801/blog/2019637
https://txc.qq.com/products/762763/blog/2019638
https://txc.qq.com/products/762772/blog/2019639
https://txc.qq.com/products/762790/blog/2019641
https://txc.qq.com/products/762758/blog/2019640
https://txc.qq.com/products/762786/blog/2019642
https://txc.qq.com/products/762782/blog/2019643
https://txc.qq.com/products/762757/blog/2019644
https://txc.qq.com/products/762805/blog/2019645
https://txc.qq.com/products/762785/blog/2019647
https://txc.qq.com/products/762815/blog/2019646
https://txc.qq.com/products/762787/blog/2019648
https://txc.qq.com/products/762799/blog/2019649
https://txc.qq.com/products/762775/blog/2019650
https://txc.qq.com/products/762759/blog/2019651
https://txc.qq.com/products/762770/blog/2019652
https://txc.qq.com/products/762855/blog/2019654