[20211206]分析表取樣最小大小是多少.txt

[20211206]分析表取樣最小大小是多少.txt

--//別人問的問題，很容易測試出來。

1.環境：
SCOTT@book> @ ver1
PORT_STRING                    VERSION        BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx            11.2.0.4.0     Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

2.測試：
SCOTT@book> execute sys.dbms_stats.gather_table_stats ( OwnName => user,TabName => 'dept',Estimate_Percent => 0.00000000001);
BEGIN sys.dbms_stats.gather_table_stats ( OwnName => user,TabName => 'dept',Estimate_Percent => 0.00000000001); END;

*
ERROR at line 1:
ORA-20001: Illegal sample percent .00000000001: must be in the range [0.000001,100]
ORA-06512: at "SYS.DBMS_STATS", line 24281
ORA-06512: at "SYS.DBMS_STATS", line 24332
ORA-06512: at line 1

--//最小也就是1e-6.實際上你設定很小的取樣，實際取樣還是可能不同的。