在大量更新期间处理Oracle ArchiveLog

• MY_META

缺点是 ALTER TABLE 命令虽然速度很快,但在处理每个表时会短暂地锁定它。它还将使依赖于 米亚梅塔 列。

下面是该方法的演练,其中包含以下注释:

-- Set up your current state
DROP TABLE my_big_table;
CREATE TABLE my_big_table (a number, my_meta varchar2(30) not null);
INSERT INTO my_big_table (a, my_meta) SELECT rownum, 'GARBAGE' FROM dual CONNECT BY rownum <= 100000;

-- Drop the my_meta column and replace it with one having a default value
ALTER TABLE my_big_table DROP COLUMN my_meta;
ALTER TABLE my_big_table ADD my_meta  varchar2(30) default 'INITIAL_VAL_FOR_TABLE' not null;

-- Look at my table -- you will see every row has your initial value
SELECT * FROM my_big_table;

-- Update some data
update my_big_table set my_meta = 'UPDATED_VALUE' WHERE a <= 15;

-- Look at my table -- you will see every row has your initial value except the first 15.
SELECT * FROM my_big_table order by a;