SPA游标采集之去除重复

注：转：http://shsnc2014.blog.163.com/blog/static/2403690822014102411217903/

当我们做数据库升级项目的时候，我们一般会去做性能回归测试，通俗一点来说，就是把10g生产库的语句拿到11g生产环境上运行，如果发现运行过程中,由于优化器、实例参数等改变导致执行计划变化，最终导致性能退化的语句，需要拿出来单独进行分析及验证。要做这个事情，首先我们需要把我们的10g上的语句给采集出来，采集方法分为以下几种方式。

• cursor cache
• awr snapshots
• awr baselines
• another sql tuning set
• 10046 trace file(11g+)

对于大型的生产库，我们一般采集的是方式是:游标还有awr snapshots的数据。为了能够完美的抓取到全部的SQL语句，我们往往需要一天对cursor cache进行多次采集。大部分建议是放在高峰期的时候采集，这么做主要是为了防止有些SQL还没被抓取到sqlset就从shared pool中purge出去了。在这个抓取的过程中，有一个困扰的问题就是literal sql的一些语句。举个例子如下：

select * from emp where empno=1456;

select * from emp where empno=1457;

select * from emp where empno=1458;

这三个SQL语句会先后被采集进来，每天都这样采集，会导致我们的SQLSET的结果集越来越大。正常情况下，一个大型的生产库的SQL语句也就几w条而已，但是如果你的硬解析非常多的话，可能在短短的几天，你采集的语句就会突破到100w条以上。然后在做后面SQLSET转换到中转表的这个过程，会执行相当长的时间，搞不好就报ORA-01555,导致运行一段时间后无法成功转换。我在这上面被坑了好几次。可能你会说，就100w的数据，Oracle应该很快转换出来的吧。这个我得解释一下。我们的中转表里面其实包含了好几个LOB字段和特殊TYPE类型。一旦数据量大了，可以说速度完全不行。正是基于这种原因，我们需要考虑一种方式，在采集的过程中进行去除重复的操作。

我们来举个例子说明下。

1.新建SQLSET

SQL> exec dbms_sqltune.CREATE_SQLSET('sqlset1');
PL/SQL procedure successfully completed.

SQL> select * from dba_sqlset;
        ID NAME            OWNER           DESCRIPTION                    CREATED   LAST_MODI STATEMENT_COUNT
---------- --------------- --------------- ------------------------------ --------- --------- ---------------
         1 sqlset1         SYS                                            11-MAY-14 11-MAY-14               0

2.使用scott用户,执行几条语句，执行前先flush下shared pool

SQL> alter system flush shared_pool;
System altered.

connect scott/tiger
select * from emp;
select * from emp where empno=1456;
select * from emp where empno=1457;

3.使用sys用户开始采集语句

DECLARE
  mycur DBMS_SQLTUNE.SQLSET_CURSOR;
BEGIN
  OPEN mycur FOR
    SELECT value(P)
      FROM TABLE(dbms_sqltune.select_cursor_cache('parsing_schema_name in (''SCOTT'')',
                                                  NULL,
                                                  NULL,
                                                  NULL,
                                                  NULL,
                                                  1,
                                                  NULL,
                                                  'ALL')) p;
  dbms_sqltune.load_sqlset(sqlset_name     => 'sqlset1',
                           populate_cursor => mycur,
                           load_option     => 'MERGE');
  CLOSE mycur;
END;
/ 

SQL> select * from dba_sqlset;
        ID NAME            OWNER           DESCRIPTION                    CREATED   LAST_MODI STATEMENT_COUNT
---------- --------------- --------------- ------------------------------ --------- --------- ---------------
         1 sqlset1         SYS                                            11-MAY-14 11-MAY-14               9

4.查看采集结果

SQL> select sql_id,sql_text from DBA_SQLSET_STATEMENTS ;
SQL_ID        SQL_TEXT
------------- --------------------------------------------------------------------------------
1srhq04p4x0zz SELECT /* OPT_DYN_SAMP */ /*+ ALL_ROWS IGNORE_WHERE_CLAUSE NO_PARALLEL(SAMPLESUB
38mhtu5pc7d07 select * from emp where empno=1456
7hys3h7ysgf9m SELECT ATTRIBUTE,SCOPE,NUMERIC_VALUE,CHAR_VALUE,DATE_VALUE FROM SYSTEM.PRODUCT_P
a2dk8bdn0ujx7 select * from emp
bc26hcc8td76f select * from emp where empno=1457
cw6vxf0kbz3v1 SELECT CHAR_VALUE FROM SYSTEM.PRODUCT_PRIVS WHERE   (UPPER('SQL*Plus') LIKE UPPE
d6vwqbw6r2ffk SELECT USER FROM DUAL
dyk4dprp70d74 SELECT DECODE('A','A','1','2') FROM DUAL
g4y6nw3tts7cc BEGIN DBMS_APPLICATION_INFO.SET_MODULE(:1,NULL); END;

从这里我们可以观察到我们的三条语句都采集进来了。这里我们可以看到我们的literal sql，如果每天对游标采集好几次的话，我们的literal sql会越采集越多，导致SQLSET的结果集非常大。当SQL数量达到百万级别后，使得我们的转换非常慢。如何去重呢？我们看下这个DBA_SQLSET_STATEMENTS的结构。

SQL> desc DBA_SQLSET_STATEMENTS
Name                                        Null?    Type
------------------------------------------- -------- -----------------------------
SQLSET_NAME                                 NOT NULL VARCHAR2(30)
SQLSET_OWNER                                         VARCHAR2(30)
SQLSET_ID                                   NOT NULL NUMBER
SQL_ID                                      NOT NULL VARCHAR2(13)
FORCE_MATCHING_SIGNATURE                    NOT NULL NUMBER
SQL_TEXT                                             CLOB
PARSING_SCHEMA_NAME                                  VARCHAR2(30)
PARSING_SCHEMA_ID                                    NUMBER
PLAN_HASH_VALUE                             NOT NULL NUMBER
BIND_DATA                                            RAW(2000)
BINDS_CAPTURED                                       CHAR(1)
MODULE                                               VARCHAR2(64)
ACTION                                               VARCHAR2(64)
ELAPSED_TIME                                         NUMBER
CPU_TIME                                             NUMBER
BUFFER_GETS                                          NUMBER
DISK_READS                                           NUMBER
DIRECT_WRITES                                        NUMBER
ROWS_PROCESSED                                       NUMBER
FETCHES                                              NUMBER
EXECUTIONS                                           NUMBER
END_OF_FETCH_COUNT                                   NUMBER
OPTIMIZER_COST                                       NUMBER
OPTIMIZER_ENV                                        RAW(2000)
PRIORITY                                             NUMBER
COMMAND_TYPE                                         NUMBER
FIRST_LOAD_TIME                                      VARCHAR2(19)
STAT_PERIOD                                          NUMBER
ACTIVE_STAT_PERIOD                                   NUMBER
OTHER                                                CLOB
PLAN_TIMESTAMP                                       DATE
SQL_SEQ                                     NOT NULL NUMBER

SQL> select sql_id,sql_text,FORCE_MATCHING_SIGNATURE from DBA_SQLSET_STATEMENTS;
SQL_ID        SQL_TEXT                                                                            FORCE_MATCHING_SIGNATURE
------------- -------------------------------------------------------------------------------- ---------------------------
1srhq04p4x0zz SELECT /* OPT_DYN_SAMP */ /*+ ALL_ROWS IGNORE_WHERE_CLAUSE NO_PARALLEL(SAMPLESUB         4094562552765466770
38mhtu5pc7d07 select * from emp where empno=1456                                                      16946033956547040230
7hys3h7ysgf9m SELECT ATTRIBUTE,SCOPE,NUMERIC_VALUE,CHAR_VALUE,DATE_VALUE FROM SYSTEM.PRODUCT_P        10967007256268736959
a2dk8bdn0ujx7 select * from emp                                                                        7001777653489406494
bc26hcc8td76f select * from emp where empno=1457                                                      16946033956547040230
cw6vxf0kbz3v1 SELECT CHAR_VALUE FROM SYSTEM.PRODUCT_PRIVS WHERE   (UPPER('SQL*Plus') LIKE UPPE        18201431879876406267
d6vwqbw6r2ffk SELECT USER FROM DUAL                                                                   17376422952071979402
dyk4dprp70d74 SELECT DECODE('A','A','1','2') FROM DUAL                                                 1846728577492307645
g4y6nw3tts7cc BEGIN DBMS_APPLICATION_INFO.SET_MODULE(:1,NULL); END;                                   0

这里我们主要利用FORCE_MATCHING_SIGNATURE这个字段。可以看到我们的literal sql的FORCE_MATCHING_SIGNATURE的值是相同的。这里是16946033956547040230。所以我们要对这个列进行distinct，并将distinct出来的值放在一个我们自定义的Table里面。

5.去重采集

SQL> create table spaqc as select distinct FORCE_MATCHING_SIGNATURE from DBA_SQLSET_STATEMENTS;
Table created. 

SQL> select * from spaqc;
   FORCE_MATCHING_SIGNATURE
---------------------------
       18201431879876406267
        1846728577492307645
        4094562552765466770
       17376422952071979402
       10967007256268736959
        7001777653489406494
       16946033956547040230
                          0
8 rows selected.

这里需要注意一下FORCE_MATCHING_SIGNATURE为0的情况下，一般是运行PL/SQL、JOB之类的操作，这个我们不能过滤掉。所以我们要把0这行给删掉。

SQL> delete from spaqc where FORCE_MATCHING_SIGNATURE=0;
1 row deleted. 

SQL> commit;
Commit complete.

6.再次测试，看看literal sql会不会被采集。

select * from emp where empno=1458;
select * from emp where empno=1459;
select * from emp where empno=1460;
select * from emp where empno=1460 and ENAME='scott';

DECLARE
  mycur DBMS_SQLTUNE.SQLSET_CURSOR;
BEGIN
  OPEN mycur FOR
    SELECT value(P)
      FROM TABLE(dbms_sqltune.select_cursor_cache('parsing_schema_name in (''SCOTT'') and FORCE_MATCHING_SIGNATURE not in (select FORCE_MATCHING_SIGNATURE from spaqc)',
                                                  NULL,
                                                  NULL,
                                                  NULL,
                                                  NULL,
                                                  1,
                                                  NULL,
                                                  'ALL')) p;
  dbms_sqltune.load_sqlset(sqlset_name     => 'sqlset1',
                           populate_cursor => mycur,
                           load_option     => 'MERGE');
  CLOSE mycur;
END;
/
SQL> select sql_id,sql_text,FORCE_MATCHING_SIGNATURE from DBA_SQLSET_STATEMENTS ;
SQL_ID        SQL_TEXT                                                                            FORCE_MATCHING_SIGNATURE
------------- -------------------------------------------------------------------------------- ---------------------------
1srhq04p4x0zz SELECT /* OPT_DYN_SAMP */ /*+ ALL_ROWS IGNORE_WHERE_CLAUSE NO_PARALLEL(SAMPLESUB         4094562552765466770
38mhtu5pc7d07 select * from emp where empno=1456                                                      16946033956547040230
7hys3h7ysgf9m SELECT ATTRIBUTE,SCOPE,NUMERIC_VALUE,CHAR_VALUE,DATE_VALUE FROM SYSTEM.PRODUCT_P        10967007256268736959
a2dk8bdn0ujx7 select * from emp                                                                        7001777653489406494
bc26hcc8td76f select * from emp where empno=1457                                                      16946033956547040230
cw6vxf0kbz3v1 SELECT CHAR_VALUE FROM SYSTEM.PRODUCT_PRIVS WHERE   (UPPER('SQL*Plus') LIKE UPPE        18201431879876406267
d6vwqbw6r2ffk SELECT USER FROM DUAL                                                                   17376422952071979402
d8fw5smyjva0b select * from emp where empno=1460 and ENAME='scott'                                    17445701640293030006
dyk4dprp70d74 SELECT DECODE('A','A','1','2') FROM DUAL                                                 1846728577492307645
g4y6nw3tts7cc BEGIN DBMS_APPLICATION_INFO.SET_MODULE(:1,NULL); END;                                                      0 

10 rows selected.

这里我们看到literal sql没有被采集进来，我们实现了游标采集的过滤。