[20200129]子光标不共享BIND_EQUIV_FAILURE.txt

[20200129]子光标不共享bind_equiv_failure.txt

--//生产系统再次遇到大量bind_equiv_failure原因导致子光标的情况。我看了我以前测试遇到的情况。
--//链接 http://blog.itpub.net/267265/viewspace-2156139/ =>[20180613]子光标不共享bind_equiv_failure。
--//别人曾经给我建议，问题可能出在alter session set statistics_level=all;的设置上，我也重复测试看看。

1.环境:
scott@test01p> @ ver1
port_string          version    banner                                                                       con_id
-------------------- ---------- ---------------------------------------------------------------------------- ------
ibmpc/win_nt64-9.1.0 12.2.0.1.0 oracle database 12c enterprise edition release 12.2.0.1.0 - 64bit production      0

sys@test> @ hide _cursor_obsolete_threshold
name                       description                                     default_value session_value system_value isses issys_mod
-------------------------- ----------------------------------------------- ------------- ------------- ------------ ----- ---------
_cursor_obsolete_threshold number of cursors per parent before obsoletion. true          8192          8192         true  false

/*
grant execute on sys.dbms_lock to scott;

create or replace function sleep1 (seconds in number)
return number
is
d_date date;
begin
  select sysdate into d_date from dual;
  sys.dbms_lock.sleep(seconds/10);
  return seconds;
end;
/

create or replace function sleep (seconds in number)
return number
is
d_date date;
begin
  select sysdate into d_date from dual;
--//sys.dbms_lock.sleep(0.01);
  return seconds;
end;
/
*/
--//注：当时的测试因为别的原因执行如上代码，现在测试不需要。

create table t as select rownum id1,mod(rownum-1,1000)+1 id2 from dual connect by level<=2000;

scott@test01p> select * from dba_extents where owner=user and segment_name='t'
  2  @ prxx
==============================
owner                         : scott
segment_name                  : t
partition_name                :
segment_type                  : table
tablespace_name               : users
extent_id                     : 0
file_id                       : 11
block_id                      : 176
bytes                         : 65536
blocks                        : 8
relative_fno                  : 11
pl/sql procedure successfully completed.

2.建立测试脚本:
--//建立脚本by.txt,注解alter session set statistics_level=all;:
set term off
--//alter session set statistics_level=all;
variable x number;
exec :x := &&1;
select t.* from t where id2<=:x;
set term on
@ dpc '' ''
quit

--//建立shell脚本by.sh:
#!/bin/bash
# rm -f ez.txt
for i in $(seq 1000)
do
    sqlplus -s -l scott/btbtms@test01p @by.txt $i >> ez.txt
done
--//在家里的笔记本上测试有点慢，减少循环到1000次。

3.测试：
--//执行脚本by.sh.
$ grep "sql_id" ez.txt |  uniq -c
   1000 sql_id  ckynkwp4t00rz, child number 0
--//可以发现并没有产生子光标。确实像别人讲的那样。

4.继续测试:
--//修改脚本by.txt.取消注解alter session set statistics_level=all;.
set term off
alter session set statistics_level=all;
variable x number;
exec :x := &&1;
select t.* from t where id2<=:x;
set term on
@ dpc '' ''
quit

--//刷新共享池3次。
alter session set statistics_level=all;
alter session set statistics_level=all;
alter session set statistics_level=all;

$ mv ez.txt ezold.txt

--//执行脚本by.sh

$ grep "sql_id" ez.txt |  uniq -c
    500 sql_id  ckynkwp4t00rz, child number 0
     51 sql_id  ckynkwp4t00rz, child number 1
     56 sql_id  ckynkwp4t00rz, child number 2
     61 sql_id  ckynkwp4t00rz, child number 3
     67 sql_id  ckynkwp4t00rz, child number 4
     74 sql_id  ckynkwp4t00rz, child number 5
     81 sql_id  ckynkwp4t00rz, child number 6
     90 sql_id  ckynkwp4t00rz, child number 7
     20 sql_id  ckynkwp4t00rz, child number 8
--//在执行过程中,可以发现并出现大量子光标.

scott@test01p> @ share ckynkwp4t00rz
old  15:           and q.sql_id like ''&1''',
new  15:           and q.sql_id like ''ckynkwp4t00rz''',
sql_text                       = select t.* from t where id2<=:x
sql_id                         = ckynkwp4t00rz
address                        = 000007ff12b9aa10
child_address                  = 000007ff1265ede8
child_number                   = 0
load_optimizer_stats           = y
reason                         = <childnode><childnumber>0</childnumber><id>39</id><reason>bind mismatch(25)</reason><size>0x0</size><details>extended_cursor_sharing</details></childnode>
--------------------------------------------------
sql_text                       = select t.* from t where id2<=:x
sql_id                         = ckynkwp4t00rz
address                        = 000007ff12b9aa10
child_address                  = 000007ff16f0f400
child_number                   = 1
reason                         = <childnode><childnumber>1</childnumber><id>39</id><reason>bind mismatch(33)</reason><size>1x4</size><init_ranges_in_first_pass>2540213050</init_ranges_in_first_pass></childnode>
--------------------------------------------------
sql_text                       = select t.* from t where id2<=:x
sql_id                         = ckynkwp4t00rz
address                        = 000007ff12b9aa10
child_address                  = 000007ff13c989f8
child_number                   = 2
bind_equiv_failure             = y
reason                         = <childnode><childnumber>2</childnumber><id>39</id><reason>bind mismatch(33)</reason><size>1x4</size><init_ranges_in_first_pass>2841161709</init_ranges_in_first_pass></childnode>
--------------------------------------------------
...
--------------------------------------------------
sql_text                       = select t.* from t where id2<=:x
sql_id                         = ckynkwp4t00rz
address                        = 000007ff12b9aa10
child_address                  = 000007ff13f41a10
child_number                   = 8
bind_equiv_failure             = y
reason                         =
--------------------------------------------------
pl/sql procedure successfully completed.

$ grep "sql_id" ez.txt |  uniq -c | awk '{ sum=sum+$1};end {print sum}'
1000
--//正好1000次。
--//可以看出设置alter session set statistics_level=all;导致出现子光标不能共享，具体原因是什么不清楚。
--//我反复测试多次,结果都是一样。

5.建立直方图呢？

scott@test01p> execute sys.dbms_stats.gather_table_stats ( ownname => user,tabname => 't',estimate_percent => null,method_opt => 'for all columns size 1024 ',cascade => true ,no_invalidate => false)
pl/sql procedure successfully completed.
--//12c 可以支持bucket大于254.

scott@test01p> @ tab_lh scott t ''

display table_name of column_name information.
input   owner table_name column
sample  : @ tab_lh table_name [column_name]
if not input column_name ,use "" .

column_name data_type data_length n num_distinct    density sample_size trans_low trans_high  num_nulls num_buckets last_analyzed       histogram  data_default
----------- --------- ----------- - ------------ ---------- ----------- --------- ---------- ---------- ----------- ------------------- ---------- -------------------------
id1         number             22 y         2000      .0005        2000 1         2000                0        1024 2020-01-29 19:44:04 hybrid
id2         number             22 y         1000     .00025        2000 1         1000                0        1000 2020-01-29 19:44:04 frequency

--//刷新共享池3次。
alter session set statistics_level=all;
alter session set statistics_level=all;
alter session set statistics_level=all;

--//执行脚本by.txt。
set term off
--//alter session set statistics_level=all;
variable x number;
exec :x := &&1;
select t.* from t where id2<=:x;
set term on
@ dpc '' ''
quit

$ mv ez.txt ez17.txt
$ grep "sql_id" ez.txt |  uniq -c
   1000 sql_id  ckynkwp4t00rz, child number 0
--//没有子光标产生。

scott@test01p> execute sys.dbms_stats.gather_table_stats ( ownname => user,tabname => 't',estimate_percent => null,method_opt => 'for all columns size 254 ',cascade => true ,no_invalidate => false)
pl/sql procedure successfully completed.

scott@test01p> @ tab_lh scott t ''

display table_name of column_name information.
input   owner table_name column
sample  : @ tab_lh table_name [column_name]
if not input column_name ,use "" .
column_name data_type data_length n num_distinct    density sample_size trans_low trans_high num_nulls num_buckets last_analyzed       histogram data_default
----------- --------- ----------- - ------------ ---------- ----------- --------- ---------- --------- ----------- ------------------- --------- ------------
id1         number             22 y         2000      .0005        2000 1         2000               0         254 2020-01-29 20:01:43 hybrid
id2         number             22 y         1000       .001        2000 1         1000               0         254 2020-01-29 20:01:43 hybrid

--//刷新共享池3次。
alter session set statistics_level=all;
alter session set statistics_level=all;
alter session set statistics_level=all;

$ mv ez.txt ez18.txt

$ grep "sql_id" ez.txt |  uniq -c
   1000 sql_id  ckynkwp4t00rz, child number 0
--//没有子光标产生。
--//也就是与直方图无关。

6.继续测试：
--//取消直方图设置。
scott@test01p> execute sys.dbms_stats.gather_table_stats ( ownname => user,tabname => 't',estimate_percent => null,method_opt => 'for all columns size 1 ',cascade => true ,no_invalidate => false)
pl/sql procedure successfully completed.

$ cat by.txt
set term off
alter session set statistics_level=all;
variable x number;
exec :x := &&1;
select t.* from t where id1<=:x;
set term on
@ dpc '' ''
quit

$ cat by.sh
#!/bin/bash
# rm -f ez.txt
for i in $(seq 2000 )
do
   sqlplus -s -l scott/btbtms@test01p @by.txt $i >> ez.txt
done

alter system flush shared_pool;

--//注意查新条件是id1<= :x,验证在x=1000后是否出现子光标。

scott@test01p> @ share basmuva6swhg4
sql_text                       = select t.* from t where id1<=:x
sql_id                         = basmuva6swhg4
address                        = 000007ff1314e908
child_address                  = 000007ff13133298
child_number                   = 0
load_optimizer_stats           = y
reason                         = <childnode><childnumber>0</childnumber><id>39</id><reason>bind mismatch(25)</reason><size>0x0</size><details>extended_cursor_sharing</details></childnode>
--------------------------------------------------
sql_text                       = select t.* from t where id1<=:x
sql_id                         = basmuva6swhg4
address                        = 000007ff1314e908
child_address                  = 000007ff13270b40
child_number                   = 1
reason                         = <childnode><childnumber>1</childnumber><id>39</id><reason>bind mismatch(33)</reason><size>1x4</size><init_ranges_in_first_pass>3229815407</init_ranges_in_first_pass></childnode>
--------------------------------------------------
sql_text                       = select t.* from t where id1<=:x
sql_id                         = basmuva6swhg4
address                        = 000007ff1314e908
child_address                  = 000007ff1343c4a0
child_number                   = 2
bind_equiv_failure             = y
reason                         = <childnode><childnumber>2</childnumber><id>39</id><reason>bind mismatch(33)</reason><size>1x4</size><init_ranges_in_first_pass>2954937500</init_ranges_in_first_pass></childnode>
..
pl/sql procedure successfully completed.

$ grep "sql_id" ez.txt |  uniq -c
   1000 sql_id  basmuva6swhg4, child number 0
    101 sql_id  basmuva6swhg4, child number 1
    111 sql_id  basmuva6swhg4, child number 2
    122 sql_id  basmuva6swhg4, child number 3
    134 sql_id  basmuva6swhg4, child number 4
    147 sql_id  basmuva6swhg4, child number 5
    162 sql_id  basmuva6swhg4, child number 6
    178 sql_id  basmuva6swhg4, child number 7
     45 sql_id  basmuva6swhg4, child number 8

$ grep "sql_id" ez.txt |  uniq -c | awk 'begin {a=909;} {sum=sum+$1;a=a*1.10;print  sum, a }'
1000 999.9
1101 1099.89
1212 1209.88
1334 1330.87
1468 1463.95
1615 1610.35
1777 1771.38
1955 1948.52
2000 2143.37

--//可以看出一个规律返回1000条记录是第1道坎，以后大约按照0.11的比例增加(最后一行测试不足不算)。当然这仅仅是我的猜测。

7.继续测试：
--//翻转执行看看，先执行2000：
$ cat by.sh
#!/bin/bash
# rm -f ez.txt
for i in $(seq 2000 -1 1 )
do
        sqlplus -s -l scott/btbtms@test01p @by.txt $i >> ez.txt
done

$ grep "sql_id" ez.txt |  uniq -c
   2000 sql_id  basmuva6swhg4, child number 0

--//并没有产生子光标。