测量sql 解析耗费的时间比例

清空共享池，关闭，重启数据库
SQL> shutdown immediate;
SQL> startup;
开启 时间统计
SQL> set timi on
SQL> select count(*) from dba_objects;
  COUNT(*)
----------
     11308
Elapsed: 00:00:00.19
SQL> /
  COUNT(*)
----------
     11308
Elapsed: 00:00:00.03
SQL> /
  COUNT(*)
----------
     11308
Elapsed: 00:00:00.03
SQL> select 16/19 from dual;
     16/19
----------
.842105263
可以看到 解析时间 所占用了绝大部分时间 ，单凭这个实验 不能说SQL解析会占用84%的时间，不过可以肯定的是 SQL解析会占用SQL语句运行的很大部分时间。
下面来测试一下 使用绑定变量 和不使用绑定变量所SQL解析所带来的性能问题
执行两个脚本 第一个 脚本不使用绑定变量
bind1.sql脚本内容如下:
declare
type cur is ref cursor;
cur1 cur;
name varchar2(1000);
begin
for i in 1..1000 loop
open cur1 for 'select object_name from dba_objects where object_id=' || i;
fetch cur1 into name;
close cur1;
end loop;
end ;
/
bind2.sql 脚本内容：
declare
type cur is ref cursor;
cur1 cur;
name varchar2(1000);
begin
for i in 1..1000 loop
open cur1 for 'select object_name from dba_objects where object_id=:x'using i;
fetch cur1 into name;
close cur1;
end loop;
end ;
/
开始测试
SQL> alter system flush shared_pool;
System altered.
SQL> set timi on
SQL> @bind1
PL/SQL procedure successfully completed.
Elapsed: 00:00:07.51
SQL>select sql_text from v$sqlarea where sql_text like '%dba_objects%';
SQL_TEXT
----------------------------------------------------------------------------------------------------
select object_name from dba_objects where object_id=506
select object_name from dba_objects where object_id=716
select object_name from dba_objects where object_id=129
....................
可以看到 该语句解析了1000次
SQL> alter system flush shared_pool;
System altered.
SQL> @bind2
PL/SQL procedure successfully completed.
Elapsed: 00:00:00.64