Migr8.rb

Migr8.rb is a database schema version management tool.

  • Easy to install, easy to setup, and easy to start
  • No configuration file; instead, only two environment variables
  • Designed carefully to suit Git or Mercurial
  • Supports SQLite3, PostgreSQL, and MySQL
  • Written in Ruby (>= 1.8)

Quick Start

  1. Donwload migr8.rb.

    $ curl -Lo migr8.rb http://bit.ly/migr8_rb
$ chmod a+x migr8.rb
### or
$ gem install migr8

  2. Set environment variables: $MIGR8_COMMAND and $MIGR8_EDITOR.

    $ export MIGR8_COMMAND="sqlite3 dbfile1"            # for SQLite3
$ export MIGR8_COMMAND="psql -q -U user1 dbname1"   # for PostgreSQL
$ export MIGR8_COMMAND="mysql -s -u user1 dbname1"  # for MySQL

$ export MIGR8_EDITOR="open -a TextMate"     # for TextMate (MacOSX)
$ export MIGR8_EDITOR="emacsclient"          # for Emacs
$ export MIGR8_EDITOR="vim"                  # for Vim

  3. Create managiment files and table.

    $ ./migr8.rb init         # create files in current directory,
                          # and create a table in DB.

  4. Now you can manage DB schema versions.

    $ ./migr8.rb                                 # show current status
$ ./migr8.rb new -m "create 'users' table"   # create a migration
       # or  ./migr8.rb new --table=users
$ ./migr8.rb                                 # show status again
$ ./migr8.rb up                              # apply migration
$ ./migr8.rb                                 # show status again
$ ./migr8.rb hist                            # list history

  5. You may got confliction error when git rebase or git pull. In this case, you must resolve it by hand. (This is intended design.)

    $ git rebase master         # confliction!
$ ./migr8.rb hist -o        # open 'migr8/history.txt', and
                            # resolve confliction manually
$ ./migr8.rb hist           # check whether history file is valid
$ git add migr8/history.txt
$ git rebase --continue

Templating

(!!Attention!! this is experimental feature and may be changed in the future.)

It is possible to embed eRuby code into up and down scripts.

Syntax:

  • <% ... %> : Ruby statement
  • <%= ... %> : Ruby expression, escaping ' into '' (or \' on MySQL)
  • <%== ... %> : Ruby expression, no escaping

For example:

vars:
  - table: users

up: |
  insert into ${table}(name) values
  <% comma = "  " %>
  <% for name in ["Haruhi", "Mikuru", "Yuki"] %>
    <%= comma %>('<%= name %>')
    <% comma = ", " %>
  <% end %>
  ;

down: |
  <% for name in ["Haruhi", "Mikuru", "Yuki"] %>
  delete from ${table} where name = '<%= name %>';
  <% end %>

The above is the same as the following:

up: |
  insert into users(name) values
      ('Haruhi')
    , ('Mikuru')
    , ('Yuki')
  ;

down: |
  delete from users where name = 'Haruhi';
  delete from users where name = 'Mikuru';
  delete from users where name = 'Yuki';

In eRuby code, values in vars are available as instance variables. For example:

version:     uhtu4853
desc:        register members
author:      kyon
vars:
  - table:   users
  - members: [Haruhi, Mikuru, Yuki]

up: |
  <% for member in @members %>
  insert into ${table}(name) values ('<%= member %>');
  <% end %>

down: |
  <% for member in @members %>
  delete from ${table} where name = '<%= member %>';
  <% end %>

If you want to see up and down scripts rendered, run migr8.rb show action. For example:

$ ./migr8.rb show uhtu4853
version:     uhtu4853
desc:        register members
author:      kyon
vars:
  - table:     "users"
  - members:   ["Haruhi", "Mikuru", "Yuki"]

up: |
  insert into users(name) values ('Haruhi');
  insert into users(name) values ('Mikuru');
  insert into users(name) values ('Yuki');

down: |
  delete from users where name = 'Haruhi';
  delete from users where name = 'Mikuru';
  delete from users where name = 'Yuki';

Notice that migration file using eRuby code is not compatible with other Migr8 implemtation.

Tips

  • migr8.rb up -a applys all migrations, while migr8.rb up applys a migration.

  • migr8.rb -D up saves SQL executed into migr8/history.txt file.

  • migr8.rb redo is equivarent to migr8.rb down; migr8.rb up.

  • migr8.rb new -p generates migration file with plain skeleton, and migr8.rb new --table=name generates with table name.

  • migr8.rb unapply -x unapplies migration which is applied in DB but corresponding migration file doesn't exist. (Describing in detail, migr8.rb unapply -x abcd1234 runs down script in _migr_history table, while migr8.rb unapply abcd1234 runs down script in migr8/migrations/abcd1234.yaml file.) This may help you when switching Git/Hg branch.

  • migr8.rb generates sql file and run it with sql command such as psql (PostgreSQL), sqlite3 (SQLite3) or mysql (MySQL). Therefore you can use non-sql command in migration file. For example:

    up: |
  -- read data from CSV file and insert into DB (PostgreSQL)
  \copy table1 from 'file1.csv' with csv;

  • MySQL doesn't support transactional DDL. It will cause troubles when you have errors in migration script (See https://www.google.com/search?q=transactional+DDL for details). On the other hand, SQLite3 and PostgreSQL support transactional DDL, and DDL will be rollbacked when error occurred in migration script. Very good.

Usage and Actions

Usage: migr8.rb [global-options] [action [options] [...]]
  -h, --help          : show help
  -v, --version       : show version
  -D, --debug         : not remove sql file ('migr8/tmp.sql') for debug

Actions:  (default: status)
  readme              : !!READ ME AT FIRST!!
  help [action]       : show help message of action, or list action names
  init                : create necessary files and a table
  hist                : list history of versions
    -o                :   open history file with $MIGR8_EDITOR
    -b                :   rebuild history file from migration files
  new                 : create new migration file and open it by $MIGR8_EDITOR
    -m text           :   description message (mandatory)
    -u user           :   author name (default: current user)
    -v version        :   specify version number instead of random string
    -p                :   plain skeleton
    -e editor         :   editr command (such as 'emacsclient', 'open', ...)
    --table=table     :   skeleton to create table
    --column=tbl.col  :   skeleton to add column
    --index=tbl.col   :   skeleton to create index
    --unique=tbl.col  :   skeleton to add unique constraint
  show [version]      : show migration file with expanding variables
    -x                :   load values of migration from history table in DB
  edit [version]      : open migration file by $MIGR8_EDITOR
    -r N              :   edit N-th file from latest version
    -e editor         :   editr command (such as 'emacsclient', 'open', ...)
  status              : show status
  up                  : apply next migration
    -n N              :   apply N migrations
    -a                :   apply all migrations
  down                : unapply current migration
    -n N              :   unapply N migrations
    --ALL             :   unapply all migrations
  redo                : do migration down, and up it again
    -n N              :   redo N migrations
    --ALL             :   redo all migrations
  apply version ...   : apply specified migrations
  unapply version ... : unapply specified migrations
    -x                :   unapply versions with down-script in DB, not in file
  delete version ...  : delete unapplied migration file
    --Imsure          :   you must specify this option to delete migration

TODO

  • [_] write more tests
  • [_] test on windows
  • [_] implement in Python
  • [_] implement in JavaScript

Changes

Release 0.4.4 (2014-07-19)

  • [bugfix] fix redo action to run down first internally.

Release 0.4.3 (2014-02-28)

  • [bugfix] fix reporting error when there is a migration which is applied but migration file doesn't exist.

Release 0.4.2 (2014-02-05)

  • [bugfix] re-packaging gem file

Release 0.4.1 (2014-02-05)

  • [bugfix] Fix to allow migration file which contains no vars.

Release 0.4.0 (2013-11-28)

  • [enhance] RubyGems package available. You can install migr8.rb by gem install migr8.
  • [enhance] eRuby templating up and down script. See 'Templating' section of README file for details.
  • [enhance] Add new action 'show' which shows migration attributes with expanding variables (ex: ${table}) and renderting template.
  • [enhance] Add new action 'delete' which deletes unapplied migration file. Note: this action can't delete migration which is already applied.
  • [enhance] Add new option 'new -v version' in order to specify version number by yourself instead of auto-generated random string.
  • [bufix] Action 'edit version' now can open migration file even when version number in migration file is wrong.

Release 0.3.1 (2013-11-24)

  • [bugfix] Fix 'hist' action not to raise error.

Release 0.3.0 (2013-11-22)

  • [enhance] Add -x option to unapply action which unapplies migrations by down-script in DB, not in migration file. You can unapply migrations which files are missing in some reason.
  • [change] Eliminate indentation from output of 'readme' action.

Release 0.2.1 (2013-11-20)

  • [bugfix] Fix new --table=name action to set table name correctly

Release 0.2.0 (2013-11-14)

  • [enhance] Add new options to new action for some skeletons
    • new --table=table : create table
    • new --column=tbl.col : add column to table
    • new --index=tbl.col : create index on column
    • new --unique=tbl.col : add unique constraint on column
  • [enhance] Add new option hist -b action which re-generate history file.
  • [change] Change several error messages
  • [change] Tweak SQL generated on SQLite3

Release 0.1.1 (2013-11-12)

  • [IMPORTANT] Change history table schema: SORRY, YOU MUST RE-CREATE HISTORY TABLE.
  • [enhance] Fix 'up' action to save both up and down script into history table.

Release 0.1.0 (2013-11-11)

  • Public release

License

$License: MIT License $

$Copyright: copyright(c) 2013-2014 kuwata-lab.com all rights reserved $