playframework数据库管理工具 笔记（2）

# --- ！Ups 标记的sql 表示正常状态下会执行的脚本

# --- ！Downs 标记的sql表示异常时会执行的脚本（这里一般写成和上面对应的回滚sql）


1.处理并发的evolution script

现在有两个程序员A和B，他们同时提交了2.sql：

# create table User
# --- !Ups

CREATE TABLE qic_db.User (
id bigint(20) NOT NULL AUTO_INCREMENT,
email varchar(255) NOT NULL,
password varchar(255) NOT NULL,
fullname varchar(255) NOT NULL,
isAdmin boolean NOT NULL,
PRIMARY KEY (id)
);

# --- !Downs
DROP TABLE qic_db.User;

# add anther column to User6
# --- !Ups

ALTER TABLE User6 ADD company varchar(255);

# --- !Downs
ALTER TABLE User6 drop company;

那么A在更新的时候就会要求merge it ，现在他只需要
# create table User
# ADD anther column to User6
# --- !Ups

CREATE TABLE qic_db.User (
id bigint(20) NOT NULL AUTO_INCREMENT,
email varchar(255) NOT NULL,
password varchar(255) NOT NULL,
fullname varchar(255) NOT NULL,
isAdmin boolean NOT NULL,
PRIMARY KEY (id)
);

ALTER TABLE User6 ADD company varchar(255);

# --- !Downs
DROP TABLE qic_db.User;
ALTER TABLE User6 drop company;实验表明：play先会回滚A的2.sql ，执行

DROP TABLE qic_db.User;

然后再执行合并后的2.sql。

2.处理错误的evolution script

当出现了一个错误的evolution script 3.sql：

# Add another column to User

# --- !Ups
ALTER TABLE User ADD company varchar(255);

# --- !Downs
ALTER TABLE User DROP company;Play 会提示你



你需要修改3.sql，点击”make it resolved“然后执行你修改过的sql。

3.在prod(生产模式)下的evolution commands

在prod环境中 如果目录下有evolution script 没有被执行过，运行run命令时play会提示 

~ _ _
~ _ __ | | __ _ _ _| |
~ | '_ \| |/ _' | || |_|
~ | __/|_|\____|\__ (_)
~ |_| |__/
~
~ play! master-localbuild, http://www.playframework.org ~ framework ID is prod
~
~ Ctrl+C to stop
~
13:33:22 INFO ~ Starting ~/test
13:33:22 INFO ~ Precompiling ...
13:33:24 INFO ~ Connected to jdbc:mysql://localhost
13:33:24 WARN ~
13:33:24 WARN ~ Your database is not up to date.
13:33:24 WARN ~ Use `play evolutions` command to manage database evolutions.
13:33:24 ERROR ~

@662c6n234
Can't start in PROD mode with errors

Your database needs evolution!
An SQL script will be run on your database.

play.db.Evolutions$InvalidDatabaseRevision
at play.db.Evolutions.checkEvolutionsState(Evolutions.java:323)
at play.db.Evolutions.onApplicationStart(Evolutions.java:197)
at play.Play.start(Play.java:452)
at play.Play.init(Play.java:298)
at play.server.Server.main(Server.java:141)
Exception in thread "main" play.db.Evolutions$InvalidDatabaseRevision
at play.db.Evolutions.checkEvolutionsState(Evolutions.java:323)
at play.db.Evolutions.onApplicationStart(Evolutions.java:197)
at play.Play.start(Play.java:452)
at play.Play.init(Play.java:298)
at play.server.Server.main(Server.java:141)

要求你先执行 play evolutions
$ play evolutions
~ _ _
~ _ __ | | __ _ _ _| |
~ | '_ \| |/ _' | || |_|
~ | __/|_|\____|\__ (_)
~ |_| |__/
~
~ play! master-localbuild, http://www.playframework.org ~ framework ID is gbo
~
~ Connected to jdbc:mysql://localhost
~ Application revision is 3 [15ed3f5] and Database revision is 0 [da39a3e]
~
~ Your database needs evolutions!

# ----------------------------------------------------------------------------

# --- Rev:1,Ups - 6b21167

CREATE TABLE User (
id bigint(20) NOT NULL AUTO_INCREMENT,
email varchar(255) NOT NULL,
password varchar(255) NOT NULL,
fullname varchar(255) NOT NULL,
isAdmin boolean NOT NULL,
PRIMARY KEY (id)
);

# --- Rev:2,Ups - 9cf7e12

ALTER TABLE User ADD age INT;
CREATE TABLE Post (
id bigint(20) NOT NULL AUTO_INCREMENT,
title varchar(255) NOT NULL,
content text NOT NULL,
postedAt date NOT NULL,
author_id bigint(20) NOT NULL,
FOREIGN KEY (author_id) REFERENCES User(id),
PRIMARY KEY (id)
);

# --- Rev:3,Ups - 15ed3f5

ALTER TABLE User ADD company varchar(255);

# ----------------------------------------------------------------------------

~ Run `play evolutions:apply` to automatically apply this script to the db
~ or apply it yourself and mark it done using `play evolutions:markApplied`
~

如果你想让play执行你的sql脚本请输入：play evolutions:apply
如果你想手动执行，play会自动忽略没有执行过sql脚本，你需要输入：play evolutions:markApplied

如果有任何错误需要回滚到以前的状态 你需要输入:play evolutions: resolve

值得一提的是：如果你删除了之前执行过的 evolution script，再次执行脚本命令时，play会自动执行被删除的sql #---! Downs下的命令