MySQL如何妥善更改大表表结构（Alter table structure of a single column

MySQL如何妥善更改大表表结构（Alter table structure of a single column

http://blog.sina.com.cn/s/blog_445e807b0101egpf.html

在网上搜到的一段很有帮助的三段脚本，贴出来供参考，以飨读者，做个笔记：
#
#  Script 1
#  Alter table structure of a single column of a large table
#
CREATE TABLE WorkingTableNew LIKE WorkingTable;
ALTER TABLE WorkingTableNew MODIFY BigColumn VARCHAR(50);
INSERT INTO WorkingTableNew SELECT * FROM WorkingTable;
ALTER TABLE WorkingTable RENAME WorkingTableOld;
ALTER TABLE WorkingTableNew RENAME WorkingTable;
DROP TABLE WorkingTableOld;
You can perform this on all slaves. What about the master ??? How do you prevent this \
from replicating to the slaves. Simple: Don't send the SQL \into the master's binary logs.\
 Simply shut off binary logging in the session before doing the ALTER TABLE stuff:
#
#  Script 2
#  Alter table structure of a single column of a large table
#  while preventing it from replicating to slaves
#
SET SQL_LOG_BIN = 0;
CREATE TABLE WorkingTableNew LIKE WorkingTable;
ALTER TABLE WorkingTableNew MODIFY BigColumn VARCHAR(50);
INSERT INTO WorkingTableNew SELECT SQL_NO_CACHE * FROM WorkingTable;
ALTER TABLE WorkingTable RENAME WorkingTableOld;
ALTER TABLE WorkingTableNew RENAME WorkingTable;
DROP TABLE WorkingTableOld;
But wait !!! What about any new data that comes in while processing these \
commands ??? Renaming the table in the beginning of the operation should do the trick. \
Let alter this code a little to prevent entering new data in that respect:
#
#  Script 3
#  Alter table structure of a single column of a large table
#  while preventing it from replicating to slaves
#  and preventing new data from entering into the old table
#
SET SQL_LOG_BIN = 0;
ALTER TABLE WorkingTable RENAME WorkingTableOld;
CREATE TABLE WorkingTableNew LIKE WorkingTableOld;
ALTER TABLE WorkingTableNew MODIFY BigColumn VARCHAR(50);
INSERT INTO WorkingTableNew SELECT SQL_NO_CACHE * FROM WorkingTableOld;
ALTER TABLE WorkingTableNew RENAME WorkingTable;
DROP TABLE WorkingTableOld;
Script 1 can be executed on any slave that do not have binary logs enabled
Script 2 can be executed on any slave that does have binary logs enabled
Script 3 can be executed on a master or anywhere else