生产环境sql语句调优实战第三篇(r2笔记38天)

生产环境有一条sql语句执行比较频繁，占用了大量的cpu资源。原本执行需要花费11秒。在一次排查中引起了我的注意，决定看看cpu消耗到底在哪儿？ sql语句是比较简单的，通过查询SUBSCRIBER_FA_V是一个视图。在视图中关联了几个和业务核心表。

SELECT TO_CHAR(SUBSCRIBER_NO) SUBSCRIBER_ID,
       SUB_STATUS,
       SUB_STS_RSN_CD,
       TO_CHAR(SUB_STATUS_DATE, 'yyyyMMdd') SUB_STATUS_DATE,
       SUBSCRIBER_TYPE
  FROM SUBSCRIBER_FA_V
 WHERE BAN = :1
   AND ROWNUM <= :2
   AND SUB_STATUS NOT IN ('C', 'L', 'T')
 ORDER BY INIT_ACT_DATE, SUBSCRIBER_NO

如果想做sql检查，对于sql中传入的变量，sql monitor提供了很方便的功能。 Binds

很清晰看到正在执行的sql语句对应的变量值。 还是来看看执行计划。 SQL Plan Monitoring Details (Plan Hash Value=1125972187)

性能瓶颈都在几个全表扫描和一个分析函数相关的rank操作中。毕竟返回的记录数只有1条。如果过多的资源都消耗在一些不正确的连接访问中，是完全可以避免的。 视图的内容如下： SELECT xxxxxxx 1 RANK FROM subscriber, distribute ed, channel cpc WHERE cpc.pym_channel_no = ed.target_pcn AND ed.agreement_no = subscriber.subscriber_no AND eg_dist_type = 'D' AND ed.expiration_date IS NULL AND SUBSCRIBER.SUB_STATUS NOT IN ('C', 'L', 'T') UNION SELECT xxxxxxx FROM (SELECT cpc.ban, subscriber.prim_resource_val, subscriber.init_act_date, SUBSCRIBER.CUSTOMER_ID, subscriber.subscriber_no, SUBSCRIBER.SUBSCRIBER_TYPE, SUBSCRIBER.SUB_STATUS, SUBSCRIBER.SUB_STS_RSN_CD, SUBSCRIBER.SUB_STATUS_DATE, SUBSCRIBER.EFFECTIVE_DATE, ROW_NUMBER () OVER ( PARTITION BY subscriber.subscriber_no ORDER BY ed.expiration_date, subscriber.subscriber_no DESC) AS RANK FROM subscriber, distribute ed, channel cpc WHERE cpc.pym_channel_no = ed.target_pcn AND ed.agreement_no = subscriber.subscriber_no AND eg_dist_type = 'D' AND SUBSCRIBER.SUB_STATUS IN ('C', 'L', 'T')) WHERE RANK = 1 根据执行计划，出问题的正式标黄的union子句。 根据传入的参数，是可以走索引的，但是在Union子句中，嵌入了子查询，导致在整个视图在数据的访问中，先全表扫描整个子查询，然后再匹配传入的参数。 视图的内容是不能随便改的，可能在这种场景中合适，其他的相关查询就有问题了。 所以尝试把视图的内容直接转换成直接的sql,标黄的部分是做的相应改动。 select xxxxxxx from (SELECT xxxxxxx 1 RANK FROM subscriber, event_distribute ed, csm_pay_channel cpc WHERE cpc.pym_channel_no = ed.target_pcn AND ed.agreement_no = subscriber.subscriber_no AND eg_dist_type = 'D' AND ed.expiration_date IS NULL AND SUBSCRIBER.SUB_STATUS NOT IN ('C', 'L', 'T') and cpc.ban = 10308170 UNION SELECT "SUBSCRIBER_NO", "INIT_ACT_DATE", "SUB_STATUS", "SUB_STS_RSN_CD", "SUB_STATUS_DATE", "SUBSCRIBER_TYPE", "RANK" FROM (SELECT subscriber.subscriber_no, SUBSCRIBER.INIT_ACT_DATE, SUBSCRIBER.SUBSCRIBER_TYPE, SUBSCRIBER.SUB_STATUS, SUBSCRIBER.SUB_STS_RSN_CD, SUBSCRIBER.SUB_STATUS_DATE, ROW_NUMBER() OVER(PARTITION BY subscriber.subscriber_no ORDER BY ed.expiration_date, subscriber.subscriber_no DESC) AS RANK FROM subscriber, event_distribute ed, csm_pay_channel cpc WHERE cpc.pym_channel_no = ed.target_pcn AND ed.agreement_no = subscriber.subscriber_no AND eg_dist_type = 'D' AND SUBSCRIBER.SUB_STATUS IN ('C', 'L', 'T') and cpc.ban = 10308170) WHERE RANK = 1) where SUB_STATUS NOT IN ('C','L','T') and rownum < 6 ORDER BY INIT_ACT_DATE, SUBSCRIBER_ID 看似语句挺长的，但是走了索引执行效率还是很高的。

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Statistics

----------------------------------------------------------

0 recursive calls

0 db block gets

22 consistent gets

0 physical reads

0 redo size

857 bytes sent via SQL*Net to client

520 bytes received via SQL*Net from client

2 SQL*Net roundtrips to/from client

3 sorts (memory)

0 sorts (disk)

1 rows processed