数据迁移

软件的维护是很繁重的工作，你可能不时的需要给你的数据库打补丁，比如新加、修改或者删除一些字段。用户Pop来管理数据迁移会比较简单一些。

我们可以用fizz创建一个数据迁移，fizz是一种描述数据库变动的语言。

描述迁移

soda 是嵌入在buffalo中的，可以独立使用，来代替使用 buffalo pop。

Fizz

运行fizz创建数据迁移的时候，会产生up和down两个文件。

$ soda generate fizz name_of_migration

运行上面的命令，将产生两个空的文件：

/migrations/20160815134952_name_of_migration.up.fizz
./migrations/20160815134952_name_of_migration.down.fizz

关于用法，可以使用help查看

$ soda g migration --help

Generates Up/Down migrations for your database using fizz.

Usage:
  soda generate fizz [name] [flags]

Aliases:
  fizz, migration

Flags:
  -h, --help   help for fizz

Global Flags:
  -c, --config string   The configuration file you would like to use.
  -d, --debug           Use debug/verbose mode
  -e, --env string      The environment you want to run migrations against. Will use $GO_ENV if set. (default "development")
  -p, --path string     Path to the migrations folder (default "./migrations")

默认会产生三个字段，UUID格式的id主键字段，datetime格式的created_at和updated_at字段。当然如果需要，你可以覆盖他。

SQL

如果你不想使用fizz，或者你有负责的语句要执行，也可以使用sql语句。

$ soda generate sql name_of_migration

将生成两个文件

./migrations/20160815134952_name_of_migration.up.sql
./migrations/20160815134952_name_of_migration.down.sql

可以通过help查看sql命令的用法

$ soda g sql --help

Generates Up/Down migrations for your database using SQL.

Usage:
  soda generate sql [name] [flags]

Flags:
  -h, --help   help for sql

Global Flags:
  -c, --config string   The configuration file you would like to use.
  -d, --debug           Use debug/verbose mode
  -e, --env string      The environment you want to run migrations against. Will use $GO_ENV if set. (default "development")
  -p, --path string     Path to the migrations folder (default "./migrations")

运行迁移

迁移

一旦迁移语句写完了，就可以执行迁移了。

$ soda migrate
$ soda migrate up

这两个命令是一样的，第一个是第二个的缩写。

回滚

当迁移完成发现一些问题的话，可以回滚。

soda migrate down

该命令的更多用户可以通过help查看

$ soda migrate --help

Runs migrations against your database.

Usage:
  soda migrate [flags]
  soda migrate [command]

Aliases:
  migrate, m

Available Commands:
  down        Apply one or more of the 'down' migrations.
  reset       The equivalent of running `migrate down` and then `migrate up`
  status      Displays the status of all migrations.
  up          Apply all of the 'up' migrations.

Flags:
  -h, --help   help for migrate

Global Flags:
  -c, --config string   The configuration file you would like to use.
  -d, --debug           Use debug/verbose mode
  -e, --env string      The environment you want to run migrations against. Will use $GO_ENV if set. (default "development")
  -p, --path string     Path to the migrations folder (default "./migrations")

Use "soda migrate [command] --help" for more information about a command.

自定义迁移记录表

默认情况下，应用的迁移记录记录在schema_migration表中。如果数据库中没有这个表，pop会自动创建他。

有时候我们需要修改跟踪迁移记录的表名。在pop v4.5.0版本之后是可以自定义的。

development:
  dialect: "postgres"
  url: "your_db_development"
  options:
    migration_table_name: migrations

部署的时候使用迁移

buffalo build后的二进制文件是包括了迁移文件的。所以在部署的时候，可以直接迁移。

$ ./myapp migrate
DEBU[2018-01-12T06:14:20Z] select count(*) as row_count from (SELECT schema_migration.* FROM schema_migration AS schema_migration WHERE version = ?) a $1=20171213171622
DEBU[2018-01-12T06:14:20Z] select count(*) as row_count from (SELECT schema_migration.* FROM schema_migration AS schema_migration WHERE version = ?) a $1=20171213172104
DEBU[2018-01-12T06:14:20Z] select count(*) as row_count from (SELECT schema_migration.* FROM schema_migration AS schema_migration WHERE version = ?) a $1=20171213172249
DEBU[2018-01-12T06:14:20Z] select count(*) as row_count from (SELECT schema_migration.* FROM schema_migration AS schema_migration WHERE version = ?) a $1=20171213173148
DEBU[2018-01-12T06:14:20Z] select count(*) as row_count from (SELECT schema_migration.* FROM schema_migration AS schema_migration WHERE version = ?) a $1=20171219070903
DEBU[2018-01-12T06:14:20Z] select count(*) as row_count from (SELECT schema_migration.* FROM schema_migration AS schema_migration WHERE version = ?) a $1=20171219071524

0.0010 seconds