SPA游标采集之去除重复

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。

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