![[20200129]子光标不共享BIND_EQUIV_FAILURE.txt](/upload/202205/01/35qov1nzuaq.jpg)
[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
--//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 =
--------------------------------------------------
SQL_TEXT = SElect t.* from t where id2<=:x
SQL_ID = ckynkwp4t00rz
ADDRESS = 000007FF12B9AA10
CHILD_ADDRESS = 000007FF16F0F400
CHILD_NUMBER = 1
REASON =
--------------------------------------------------
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 =
--------------------------------------------------
...
--------------------------------------------------
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 =
--------------------------------------------------
SQL_TEXT = SElect t.* from t where id1<=:x
SQL_ID = basmuva6swhg4
ADDRESS = 000007FF1314E908
CHILD_ADDRESS = 000007FF13270B40
CHILD_NUMBER = 1
REASON =
--------------------------------------------------
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 =
..
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。
![[20200129]子光标不共享BIND_EQUIV_FAILURE.txt](/upload/202205/01/gt2y25y0t3h.jpg)
