Oracle 基于事务临时表11g和12C下，能看到临时表后收集的统计数据，前者记录被清除，后者没有，这是一个很重要的不同。
关于使用企业环境12C，11g，使用暂时表会造成时快时慢。之前我有帖子http://blog.csdn.net/stevendbaguo/article/details/39964807。用了hint之后，也不是特别好。于是直接採集，结果暂时表被清空。
解决办法是：建基于session的暂时表，且每次用完之后要truncate，要不然，会有问题。
SQL> select * from v$version;
BANNER CON_ID-------------------------------------------------------------------------------- ----------
Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production 0
PL/SQL Release 12.1.0.1.0 - Production 0
CORE 12.1.0.1.0Production 0
TNS for Linux: Version 12.1.0.1.0 - Production 0
NLSRTL Version 12.1.0.1.0 - Production 0
SQL> drop table test purge;
--基于事务的暂时表
SQL> create global temporary table test
(
ID number
)
on commit delete rows;
SQL> insert into test select object_id from dba_objects;
99412 rows inserted
SQL> select count(1) from test;
COUNT(1)
----------
99412
SQL> exec dbms_stats.gather_table_stats(user,'test');
SQL> select count(1) from test;
COUNT(1)
----------
99412
SQL> select * from v$version;
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - 64bit Production
PL/SQL Release 11.2.0.1.0 - Production
CORE 11.2.0.1.0Production
TNS for Linux: Version 11.2.0.1.0 - Production
NLSRTL Version 11.2.0.1.0 - Production
SQL> drop table test purge;
--基于事务的暂时表
SQL> create global temporary table test
(
ID number
)
on commit delete rows;
SQL> insert into test select object_id from dba_objects;
70379 rows inserted
SQL> select count(1) from test;
COUNT(1)
----------
70379
SQL> exec dbms_stats.gather_table_stats(user,'test');
SQL> select count(1) from test;
COUNT(1)
----------
0