Oracle 快速Drop大表

周末一兄弟问我有个近200G的表想要DROP，但是他就算先truncate再drop，或是先offline，再drop，都要话费很长时间，之后又试了分批回缩，发现效果要快很多，只是步骤比较麻烦一点。

SQL> set timing on
SQL> select * from dual;
DUMMY
-----
X
已执行耗时 0.468 秒
SQL> truncate table subscription_history_old reuse storage;
表被截短
已执行耗时 2.984 秒
SQL>
SQL> SELECT bytes/1024/1024/1024,a.owner,a.segment_name FROM Dba_Segments a
2 WHERE segment_name LIKE '%SUBSCRIPTION_HISTORY_OLD%';
BYTES/1024/1024/1024 OWNER SEGMENT_NAME
-------------------- ------------------------------ --------------------------------------------------------------------------------
178.705078125 MISC SUBSCRIPTION_HISTORY_OLD
已执行耗时 0.266 秒
SQL> ALTER table subscription_history_old DEALLOCATE UNUSED KEEP 177000M;
表被改变
已执行耗时 1.468 秒
SQL> ALTER table subscription_history_old DEALLOCATE UNUSED KEEP 172000M;
表被改变
已执行耗时 0.782 秒
SQL> ALTER table subscription_history_old DEALLOCATE UNUSED KEEP 162000M;
表被改变
已执行耗时 1.735 秒
SQL> ALTER table subscription_history_old DEALLOCATE UNUSED KEEP 142000M;
表被改变
已执行耗时 3.672 秒
SQL> ALTER table subscription_history_old DEALLOCATE UNUSED KEEP 122000M;
表被改变
已执行耗时 4.984 秒
SQL> ALTER table subscription_history_old DEALLOCATE UNUSED KEEP 102000M;
表被改变
已执行耗时 5.25 秒
SQL> ALTER table subscription_history_old DEALLOCATE UNUSED KEEP 82000M;
表被改变
已执行耗时 5.125 秒
SQL> ALTER table subscription_history_old DEALLOCATE UNUSED KEEP 62000M;
表被改变
已执行耗时 5.063 秒
SQL> ALTER table subscription_history_old DEALLOCATE UNUSED KEEP 42000M;
表被改变
已执行耗时 4.375 秒
SQL> ALTER table subscription_history_old DEALLOCATE UNUSED KEEP 22000M;
表被改变
已执行耗时 4.703 秒
SQL> ALTER table subscription_history_old DEALLOCATE UNUSED KEEP 2000M;
表被改变
已执行耗时 4.187 秒
SQL> ALTER table subscription_history_old DEALLOCATE UNUSED KEEP 500M;
表被改变
已执行耗时 0.375 秒
SQL>
SQL> SELECT bytes/1024/1024/1024,a.owner,a.segment_name FROM Dba_Segments a
2 WHERE segment_name LIKE '%SUBSCRIPTION_HISTORY_OLD%';
BYTES/1024/1024/1024 OWNER SEGMENT_NAME
-------------------- ------------------------------ --------------------------------------------------------------------------------
0.48834228515625 MISC SUBSCRIPTION_HISTORY_OLD
已执行耗时 1.688 秒
SQL> drop table SUBSCRIPTION_HISTORY_OLD;
表被删掉
已执行耗时 6.453 秒
SQL>

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