[20161001]绑定变量的分配长度5.txt

[20161001]绑定变量的分配长度5.txt

--如果绑定变量中字符串分配占用空间的长度变化，oracle会建立子光标。
--一般如果绑定变量有多个字段在分配占用空间时长度变化，这样生成的子光标会增加。
--我以前的测试字符串长度变化是32，32+96=128,32+96+1872=2000.也就是分4个段 1-32,33-128,129-2000,2001-4000.
--相关链接：
http://blog.itpub.net/267265/viewspace-1993495/
http://blog.itpub.net/267265/viewspace-2024389/
http://blog.itpub.net/267265/viewspace-2050886/
http://blog.itpub.net/267265/viewspace-2056695/

--本测试看看2个绑定变量能产生多少子光标，按照道理应该产生4*4=16个子光标。实际上别人的测试并不会产生16个子光标，
--出于好奇没事，我自己也测试看看。

1.环境：
SCOTT@test01p> @ ver1
PORT_STRING                    VERSION        BANNER                                                                               CON_ID
------------------------------ -------------- -------------------------------------------------------------------------------- ----------
IBMPC/WIN_NT64-9.1.0           12.1.0.1.0     Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production              0

SCOTT@test01p> create table t (c1 varchar2(4000),c2 varchar2(4000),c3 varchar2(4000),c4 varchar2(4000),c5 varchar2(4000));
Table created.

--//前面我的测试
--字符串长度变化是32，32+96=128,32+96+1872=2000.也就是分4个段 1-32,33-128,129-2000,2001-4000.
--这样如果2个字段varchar2(4000)，理论讲可以出现4*4=16个子光标，测试看看是否正确。

SYS@test> alter system set "_cursor_bind_capture_area_size"=8000 scope=memory;
alter system set "_cursor_bind_capture_area_size"=8000 scope=memory
*
ERROR at line 1:
ORA-00068: invalid value 8000 for parameter _cursor_bind_capture_area_size, must be between 0 and 3999

SYS@test> alter system set "_cursor_bind_capture_area_size"=3999 scope=memory;
System altered.
--//改变 _cursor_bind_capture_area_size，保证能捕获绑定变量的值。

2.测试脚本一：

SCOTT@test01p> alter system flush shared_pool;
System altered.

declare
v_c1 varchar2(4000);
v_c2 varchar2(4000);
begin
   v_c1 := rpad('0',32);
   v_c2 := rpad('0',32);
   execute immediate 'select count(*) from t where c1=:instring1 and c2=:instring2' using v_c1,v_c2 ;

   v_c1 := rpad('1',32);
   v_c2 := rpad('1',128);
   execute immediate 'select count(*) from t where c1=:instring1 and c2=:instring2' using v_c1,v_c2 ;

   v_c1 := rpad('2',128);
   v_c2 := rpad('2',32);
   execute immediate 'select count(*) from t where c1=:instring1 and c2=:instring2' using v_c1,v_c2 ;

   v_c1 := rpad('3',128);
   v_c2 := rpad('3',128);
   execute immediate 'select count(*) from t where c1=:instring1 and c2=:instring2' using v_c1,v_c2 ;
end;
/
commit;
--确定sql_id='2z6faqbzrf9jg'.

SCOTT@test01p> select sql_id, child_number, executions  from v$sql where sql_id = '2z6faqbzrf9jg';
SQL_ID        CHILD_NUMBER EXECUTIONS
------------- ------------ ----------
2z6faqbzrf9jg            0          1
                         1          1
                         2          2
--仅仅3个子光标，why?

SCOTT@test01p> @ bind_cap 2z6faqbzrf9jg
C200
------------------------------------------------------------
select count(*) from t where c1=:instring1 and c2=:instring2

SQL_ID        CHILD_NUMBER WAS NAME                   POSITION MAX_LENGTH LAST_CAPTURED       DATATYPE_STRING VALUE_STRING
------------- ------------ --- -------------------- ---------- ---------- ------------------- --------------- ---------------------------------
2z6faqbzrf9jg            0 YES :INSTRING1                    1         32 2016-10-01 19:42:46 VARCHAR2(32)    0
                           YES :INSTRING2                    2         32 2016-10-01 19:42:46 VARCHAR2(32)    0

                         1 YES :INSTRING1                    1         32 2016-10-01 19:42:46 VARCHAR2(32)    1
                           YES :INSTRING2                    2        128 2016-10-01 19:42:46 VARCHAR2(128)   1

                         2 YES :INSTRING1                    1        128 2016-10-01 19:42:46 VARCHAR2(128)   2
                           YES :INSTRING2                    2        128 2016-10-01 19:42:46 VARCHAR2(128)   2
6 rows selected.

--//会是因为第2次执行时已经赋值v_c2 := rpad('1',128)。

3.建立脚本方便测试:
D:\tools\rlwrap> cat bbb.sql
declare
v_c1 varchar2(4000);
v_c2 varchar2(4000);
begin
   execute immediate 'select count(*) from t where c1=:instring1 and c2=:instring2' using rpad('1',&&1),rpad('1',&&2);
end;
/
--quit;

alter system flush shared_pool;
alter system flush shared_pool;

@ bbb.sql 1 1
@ bbb.sql 1 33
@ bbb.sql 33 1
@ bbb.sql 33 33

SCOTT@test01p> @bind_cap 2z6faqbzrf9jg
C200
------------------------------------------------------------
select count(*) from t where c1=:instring1 and c2=:instring2

SQL_ID        CHILD_NUMBER WAS NAME                   POSITION MAX_LENGTH LAST_CAPTURED       DATATYPE_STRING VALUE_STRING
------------- ------------ --- -------------------- ---------- ---------- ------------------- --------------- ---------------
2z6faqbzrf9jg            0 YES :INSTRING1                    1         32 2016-10-01 21:12:53 VARCHAR2(32)    1
                           YES :INSTRING2                    2         32 2016-10-01 21:12:53 VARCHAR2(32)    1

                         1 YES :INSTRING1                    1         32 2016-10-01 21:12:53 VARCHAR2(32)    1
                           YES :INSTRING2                    2        128 2016-10-01 21:12:53 VARCHAR2(128)   1

                         2 YES :INSTRING1                    1        128 2016-10-01 21:12:53 VARCHAR2(128)   1
                           YES :INSTRING2                    2        128 2016-10-01 21:12:53 VARCHAR2(128)   1

--//依旧是3个子光标。

alter system flush shared_pool;
@ bbb.sql 1 1
@ bbb.sql 33 1
@ bbb.sql 1 33
@ bbb.sql 33 33

SCOTT@test01p> @bind_cap 2z6faqbzrf9jg
C200
------------------------------------------------------------
select count(*) from t where c1=:instring1 and c2=:instring2

SQL_ID        CHILD_NUMBER WAS NAME                   POSITION MAX_LENGTH LAST_CAPTURED       DATATYPE_STRING VALUE_STRING
------------- ------------ --- -------------------- ---------- ---------- ------------------- --------------- --------------------
2z6faqbzrf9jg            0 YES :INSTRING1                    1         32 2016-10-01 21:15:07 VARCHAR2(32)    1
                           YES :INSTRING2                    2         32 2016-10-01 21:15:07 VARCHAR2(32)    1

                         1 YES :INSTRING1                    1        128 2016-10-01 21:15:07 VARCHAR2(128)   1
                           YES :INSTRING2                    2         32 2016-10-01 21:15:07 VARCHAR2(32)    1

                         2 YES :INSTRING1                    1        128 2016-10-01 21:15:07 VARCHAR2(128)   1
                           YES :INSTRING2                    2        128 2016-10-01 21:15:07 VARCHAR2(128)   1

SCOTT@test01p> select sql_id, child_number, executions  from v$sql where sql_id = '2z6faqbzrf9jg';
SQL_ID        CHILD_NUMBER EXECUTIONS
------------- ------------ ----------
2z6faqbzrf9jg            0          1
                         1          1
                         2          2

--视乎从上面的测试得到一个规律,文字比较难描述。
--当执行@ bbb.sql 1 33,如果没有其他子光标的情况下应该如下：

SCOTT@test01p> @bind_cap 2z6faqbzrf9jg
C200
------------------------------------------------------------
select count(*) from t where c1=:instring1 and c2=:instring2

SQL_ID        CHILD_NUMBER WAS NAME                   POSITION MAX_LENGTH LAST_CAPTURED       DATATYPE_STRING VALUE_STRING
------------- ------------ --- -------------------- ---------- ---------- ------------------- --------------- ----------------
2z6faqbzrf9jg            0 YES :INSTRING1                    1         32 2016-10-01 21:34:50 VARCHAR2(32)    1
                           YES :INSTRING2                    2        128 2016-10-01 21:34:50 VARCHAR2(128)   1

--而因为存在子光标CHILD_NUMBER=1
SQL_ID        CHILD_NUMBER WAS NAME                   POSITION MAX_LENGTH LAST_CAPTURED       DATATYPE_STRING VALUE_STRING
------------- ------------ --- -------------------- ---------- ---------- ------------------- --------------- --------------------
2z6faqbzrf9jg            1 YES :INSTRING1                    1        128 2016-10-01 21:15:07 VARCHAR2(128)   1
                           YES :INSTRING2                    2         32 2016-10-01 21:15:07 VARCHAR2(32)    1

--这样生成新的子光标DATATYPE_STRING都是VARCHAR2(128)，也就是生成的DATATYPE_STRING要大于前面的子光标。

4.根据这个规律，在排列组合看看：

alter system flush shared_pool;
@bbb.sql 1 1
@bbb.sql 1 33
@bbb.sql 33 1
@bbb.sql 33 33

@bbb.sql 1 129
@bbb.sql 33 129
@bbb.sql 129 1
@bbb.sql 129 33
@bbb.sql 129 129

@bbb.sql 1 2001
@bbb.sql 33 2001
@bbb.sql 129 2001
@bbb.sql 2001 1
@bbb.sql 2001 33
@bbb.sql 2001 129
@bbb.sql 2001 2001

--按照这个组合应该是7个子光标。

SCOTT@test01p> @bind_cap 2z6faqbzrf9jg

C200
------------------------------------------------------------
select count(*) from t where c1=:instring1 and c2=:instring2

SQL_ID        CHILD_NUMBER WAS NAME                   POSITION MAX_LENGTH LAST_CAPTURED       DATATYPE_STRING VALUE_STRING
------------- ------------ --- -------------------- ---------- ---------- ------------------- --------------- ---------------------------------
2z6faqbzrf9jg            0 YES :INSTRING1                    1         32 2016-10-01 21:53:03 VARCHAR2(32)    1
                           YES :INSTRING2                    2         32 2016-10-01 21:53:03 VARCHAR2(32)    1

                         1 YES :INSTRING1                    1         32 2016-10-01 21:53:03 VARCHAR2(32)    1
                           YES :INSTRING2                    2        128 2016-10-01 21:53:03 VARCHAR2(128)   1

                         2 YES :INSTRING1                    1        128 2016-10-01 21:53:03 VARCHAR2(128)   1
                           YES :INSTRING2                    2        128 2016-10-01 21:53:03 VARCHAR2(128)   1

                         3 YES :INSTRING1                    1        128 2016-10-01 21:53:03 VARCHAR2(128)   1
                           YES :INSTRING2                    2       2000 2016-10-01 21:53:03 VARCHAR2(2000)  1

                         4 YES :INSTRING1                    1       2000 2016-10-01 21:53:03 VARCHAR2(2000)  1
                           YES :INSTRING2                    2       2000 2016-10-01 21:53:03 VARCHAR2(2000)  1

                         5 YES :INSTRING1                    1       2000 2016-10-01 21:53:03 VARCHAR2(2000)  1
                           YES :INSTRING2                    2       4000 2016-10-01 21:53:03 VARCHAR2(4000)  1

                         6 YES :INSTRING1                    1       4000 2016-10-01 21:53:03 VARCHAR2(4000)  1
                           YES :INSTRING2                    2       4000 2016-10-01 21:53:03 VARCHAR2(4000)  1
14 rows selected.

SCOTT@test01p> select sql_id, child_number, executions  from v$sql where sql_id = '2z6faqbzrf9jg';
SQL_ID        CHILD_NUMBER EXECUTIONS
------------- ------------ ----------
2z6faqbzrf9jg            0          1
                         1          1
                         2          2
                         3          2
                         4          3
                         5          3
                         6          4
7 rows selected.

--总结：
--大家可以尝试各种组合，我的测试最大就是7个。

alter system flush shared_pool;
@bbb.sql 1 1
@bbb.sql 1 33
@bbb.sql 1 129
@bbb.sql 1 2001

@bbb.sql 33 1
@bbb.sql 33 33
@bbb.sql 33 129
@bbb.sql 33 2001

@bbb.sql 129 1
@bbb.sql 129 33
@bbb.sql 129 129
@bbb.sql 129 2001

@bbb.sql 2001 1
@bbb.sql 2001 33
@bbb.sql 2001 129
@bbb.sql 2001 2001


SCOTT@test01p> @bind_cap 2z6faqbzrf9jg
C200
------------------------------------------------------------
select count(*) from t where c1=:instring1 and c2=:instring2

SQL_ID        CHILD_NUMBER WAS NAME                   POSITION MAX_LENGTH LAST_CAPTURED       DATATYPE_STRING VALUE_STRING
------------- ------------ --- -------------------- ---------- ---------- ------------------- --------------- --------------------------------
2z6faqbzrf9jg            0 YES :INSTRING1                    1         32 2016-10-01 22:00:32 VARCHAR2(32)    1
                           YES :INSTRING2                    2         32 2016-10-01 22:00:32 VARCHAR2(32)    1

                         1 YES :INSTRING1                    1         32 2016-10-01 22:00:32 VARCHAR2(32)    1
                           YES :INSTRING2                    2        128 2016-10-01 22:00:32 VARCHAR2(128)   1

                         2 YES :INSTRING1                    1         32 2016-10-01 22:00:32 VARCHAR2(32)    1
                           YES :INSTRING2                    2       2000 2016-10-01 22:00:32 VARCHAR2(2000)  1

                         3 YES :INSTRING1                    1         32 2016-10-01 22:00:32 VARCHAR2(32)    1
                           YES :INSTRING2                    2       4000 2016-10-01 22:00:32 VARCHAR2(4000)  1

                         4 YES :INSTRING1                    1        128 2016-10-01 22:00:32 VARCHAR2(128)   1
                           YES :INSTRING2                    2       4000 2016-10-01 22:00:32 VARCHAR2(4000)  1

                         5 YES :INSTRING1                    1       2000 2016-10-01 22:00:33 VARCHAR2(2000)  1
                           YES :INSTRING2                    2       4000 2016-10-01 22:00:33 VARCHAR2(4000)  1

                         6 YES :INSTRING1                    1       4000 2016-10-01 22:00:33 VARCHAR2(4000)  1
                           YES :INSTRING2                    2       4000 2016-10-01 22:00:33 VARCHAR2(4000)  1
14 rows selected.

SCOTT@test01p> select sql_id, child_number, executions  from v$sql where sql_id = '2z6faqbzrf9jg';
SQL_ID        CHILD_NUMBER EXECUTIONS
------------- ------------ ----------
2z6faqbzrf9jg            0          1
                         1          1
                         2          1
                         3          1
                         4          4
                         5          4
                         6          4
7 rows selected.