如何关联执行计划和SQL查询

这是一个问题

UPDATE hrs.rns_recon_ho c SET c.refr_numb = 
(
SELECT seqn_numb FROM hrs.rns_recon_ho p WHERE p.narr_1 = c.narr_1 
AND p.seqn_numb = p.refr_numb AND p.prod_code = 0
)
Where c.prod_code = 0 And c.refr_numb = 0 
AND c.narr_1 = '3/13/201211013198693442091'

这是它的执行计划

查询的哪个部分导致表访问（完整）

编辑

我的错误，我应该更清楚。现在让我澄清一下，我需要知道如何将部分执行计划与部分查询关联起来。比如说

查询的哪个部分导致表访问（完整）

查询的哪个部分导致表访问（通过全局索引ROWID）

但是，很明显，

索引（…）…产品代码

是由产品代码字段引起的

---

是否有任何经验法则、指导方针或技巧可以识别？或者，我们无法知道，因为优化器不会告诉我们选择某个路径的原因。

可能会在一个表上通过提示强制进行完整表扫描，例如

UPDATE hrs.rns_recon_ho c SET c.refr_numb =
(
SELECT /*+ FULL(p) */ seqn_numb FROM hrs.rns_recon_ho p WHERE p.narr_1 = c.narr_1
AND p.seqn_numb = p.refr_numb AND p.prod_code = 0
)
Where c.prod_code = 0 And c.refr_numb = 0
AND c.narr_1 = '3/13/201211013198693442091'

或

如果您的执行计划显示两个“完全扫描”，您知道它最初是由另一个引起的。

让我重新创建：

CREATE TABLE RNS_RECON_HO ( PROD_CODE NUMBER,
            REFR_NUMB NUMBER,
            NARR_1 VARCHAR2 ( 25 ),
            SEQN_NUMB NUMBER primary key    );

CREATE INDEX TESTTT ON RNS_RECON_HO (PROD_CODE);
CREATE INDEX TESTTT1 ON RNS_RECON_HO (REFR_NUMB);
CREATE INDEX TESTTT2 ON RNS_RECON_HO (NARR_1);

现在复制您的计划：

SET AUTOTRACE ON

UPDATE
      RNS_RECON_HO C
SET
      C.REFR_NUMB    =
          ( SELECT
                 SEQN_NUMB
           FROM
                RNS_RECON_HO P
           WHERE
                    P.NARR_1 = C.NARR_1
                AND P.SEQN_NUMB = P.REFR_NUMB
                AND P.PROD_CODE = PROD_CODE )
WHERE
         C.PROD_CODE = 0
      AND C.REFR_NUMB = 0
      AND C.NARR_1 = '3/13/201211013198693442091';


0 rows updated.

Execution Plan
----------------------------------------------------------
   0       UPDATE STATEMENT Optimizer Mode=ALL_ROWS (Cost=2 Card=1 Bytes=78)
   1    0    UPDATE RNS_RECON_HO
   2    1      TABLE ACCESS FULL RNS_RECON_HO (Cost=2 Card=1 Bytes=78)
   3    1      TABLE ACCESS BY INDEX ROWID RNS_RECON_HO (Cost=5 Card=1 Bytes=91)
   4    3        INDEX RANGE SCAN TESTTT (Cost=1 Card=1)

Statistics
----------------------------------------------------------
        190  recursive calls
          0  spare statistic 3
          0  gcs messages sent
         25  db block gets from cache
          0  physical reads direct (lob)
          0  queue position update
          0  queue single row
          0  queue ocp pages
          0  HSC OLTP Compressed Blocks
          0  HSC IDL Compressed Blocks
          0  rows processed

原因：

优化器只会选择使用比表扫描更便宜（读取次数更少）的索引。这通常意味着WHERE子句条件需要映射到索引的前导（即最左侧）列。因此，在where子句列上添加索引（PROD_CODE、REFR_NUMB、NARR_1）可以避免这种情况

要确认，请检查此项

CREATE INDEX TESTTT3 ON RNS_RECON_HO (PROD_CODE, REFR_NUMB, NARR_1);

SET AUTOTRACE ON

UPDATE
      RNS_RECON_HO C
SET
      C.REFR_NUMB    =
          ( SELECT
                 SEQN_NUMB
           FROM
                RNS_RECON_HO P
           WHERE
                    P.NARR_1 = C.NARR_1
                AND P.SEQN_NUMB = P.REFR_NUMB
                AND P.PROD_CODE = PROD_CODE )
WHERE
         C.PROD_CODE = 0
      AND C.REFR_NUMB = 0
      AND C.NARR_1 = '3/13/201211013198693442091';

0 rows updated.

Execution Plan
----------------------------------------------------------
   0       UPDATE STATEMENT Optimizer Mode=ALL_ROWS (Cost=1 Card=1 Bytes=78)
   1    0    UPDATE RNS_RECON_HO
   2    1      INDEX RANGE SCAN TESTTT3 (Cost=1 Card=1 Bytes=78)
   3    1      TABLE ACCESS BY INDEX ROWID RNS_RECON_HO (Cost=27 Card=1 Bytes=91)
   4    3        INDEX FULL SCAN TESTTT3 (Cost=26 Card=1)

Statistics
----------------------------------------------------------
          1  recursive calls
          0  spare statistic 3
          0  gcs messages sent
          0  db block gets from cache
          0  physical reads direct (lob)
          0  queue position update
          0  queue single row
          0  queue ocp pages
          0  HSC OLTP Compressed Blocks
          0  HSC IDL Compressed Blocks
          0  rows processed

但这只是为了改变计划，但绝不承诺任何性能改进，因为您提供的投入有限

跟进：

外部查询正在进行FTS，因为它忽略了索引。因此，当我们放置复合键时，索引对于优化器来说是直接的，并且使用相同的索引。子查询正在使用索引，因为它与索引列上的外部查询联接

---

如何确定准确的计划无法100%实现，尽管您可以通过遵循核心规则接近可能的执行计划。

同样通过此

更新/*+FULL（c）FULL（p）*/hrs.rns\u recon\u ho c SET c.refr\u numb=

？当提示是内部查询时，现在有两个完整扫描。这是否意味着外部查询正在导致

FULL

scan？也通过此

UPDATE/*+FULL（p）*/hrs.rns\u recon\u ho c SET

？您的主键是什么？你有什么索引？你有分区吗？@realspirituals

seqn\u numb

是PK，所有查询的字段都被索引，表是分区的。你能发布你的创建表、索引脚本吗？或者在sqlfiddle.comBy中设置它。顺便说一句，我注意到您正在加入

seqn\u numb=refr\u numb

并更新相同的，即

refr\u numb=seqn\u numb

。你想干什么。完整表扫描将被加入

CREATE INDEX TESTTT3 ON RNS_RECON_HO (PROD_CODE, REFR_NUMB, NARR_1);

SET AUTOTRACE ON

UPDATE
      RNS_RECON_HO C
SET
      C.REFR_NUMB    =
          ( SELECT
                 SEQN_NUMB
           FROM
                RNS_RECON_HO P
           WHERE
                    P.NARR_1 = C.NARR_1
                AND P.SEQN_NUMB = P.REFR_NUMB
                AND P.PROD_CODE = PROD_CODE )
WHERE
         C.PROD_CODE = 0
      AND C.REFR_NUMB = 0
      AND C.NARR_1 = '3/13/201211013198693442091';

0 rows updated.

Execution Plan
----------------------------------------------------------
   0       UPDATE STATEMENT Optimizer Mode=ALL_ROWS (Cost=1 Card=1 Bytes=78)
   1    0    UPDATE RNS_RECON_HO
   2    1      INDEX RANGE SCAN TESTTT3 (Cost=1 Card=1 Bytes=78)
   3    1      TABLE ACCESS BY INDEX ROWID RNS_RECON_HO (Cost=27 Card=1 Bytes=91)
   4    3        INDEX FULL SCAN TESTTT3 (Cost=26 Card=1)

Statistics
----------------------------------------------------------
          1  recursive calls
          0  spare statistic 3
          0  gcs messages sent
          0  db block gets from cache
          0  physical reads direct (lob)
          0  queue position update
          0  queue single row
          0  queue ocp pages
          0  HSC OLTP Compressed Blocks
          0  HSC IDL Compressed Blocks
          0  rows processed