Name

sqitchtutorial-mysql - A tutorial introduction to Sqitch change management on MySQL

Synopsis

  sqitch *

Description

This tutorial explains how to create a sqitch-enabled MySQL project, use a VCS for deployment planning, and work with other developers to make sure changes remain in sync and in the proper order.

We'll start by creating new project from scratch, a fictional antisocial networking site called Flipr. All examples use Git <http://git-scm.com/> as the VCS and MySQL <http://dev.mysql.com/> as the storage engine.

If you'd like to manage an PostgreSQL database, see sqitchtutorial.

If you'd like to manage an SQLite database, see sqitchtutorial-sqlite.

If you'd like to manage an Oracle database, see sqitchtutorial-oracle.

If you'd like to manage an Firebird database, see sqitchtutorial-firebird.

If you'd like to manage an Vertica database, see sqitchtutorial-vertica.

Starting a New Project

Usually the first thing to do when starting a new project is to create a source code repository. So let's do that with Git:

  > mkdir flipr
  > cd flipr
  > git init .
  Initialized empty Git repository in /flipr/.git/
  > touch README.md
  > git add .
  > git commit -am 'Initialize project, add README.'
  [master (root-commit) fdf2a40] Initialize project, add README.
   1 file changed, 38 insertions(+)
   create mode 100644 README.md

If you're a Git user and want to follow along the history, the repository used in these examples is on GitHub <https://github.com/theory/sqitch-mysql-intro>.

Now that we have a repository, let's get started with Sqitch. Every Sqitch project must have a name associated with it, and, optionally, a unique URI. We recommend including the URI, as it increases the uniqueness of object identifiers internally, so let's specify one when we initialize Sqitch:

  > sqitch init flipr --uri https://github.com/theory/sqitch-mysql-intro/ --engine mysql
  Created sqitch.conf
  Created sqitch.plan
  Created deploy/
  Created revert/
  Created verify/

Let's have a look at sqitch.conf:

  > cat sqitch.conf
  [core]
        engine = mysql
        # plan_file = sqitch.plan
        # top_dir = .
  # [engine "mysql"]
        # target = db:mysql:
        # registry = sqitch
        # client = /usr/local/mysql/bin/mysql

Good, it picked up on the fact that we're creating changes for the MySQL engine, thanks to the "--engine mysql" option, and saved it to the file. Furthermore, it wrote a commented-out "[engine "mysql"]" section with all the available MySQL engine-specific settings commented out and ready to be edited as appropriate.

By default, Sqitch will read sqitch.conf in the current directory for settings. But it will also read ~/.sqitch/sqitch.conf for user-specific settings. Since MySQL's "mysql" client <https://dev.mysql.com/doc/refman/5.6/en/mysql.html> is not in the path on my system, let's go ahead an tell it where to find the client on our computer:

  > sqitch config --user engine.mysql.client /usr/local/mysql/bin/mysql

And let's also tell it who we are, since this data will be used in all of our projects:

  > sqitch config --user user.name 'Marge N. OXVera'
  > sqitch config --user user.email 'marge@example.com'

Have a look at ~/.sqitch/sqitch.conf and you'll see this:

  > cat ~/.sqitch/sqitch.conf
  [engine "mysql"]
        client = /usr/local/mysql/bin/mysql
  [user]
        name = Marge N. OXVera
        email = marge@example.com

Which means that Sqitch should be able to find "mysql" for any project, and that it will always properly identify us when planning and committing changes.

Back to the repository. Have a look at the plan file, sqitch.plan:

  > cat sqitch.plan
  %syntax-version=1.0.0
  %project=flipr
  %uri=https://github.com/theory/sqitch-mysql-intro/

Note that it has picked up on the name and URI of the app we're building. Sqitch uses this data to manage cross-project dependencies. The "%syntax-version" pragma is always set by Sqitch, so that it always knows how to parse the plan, even if the format changes in the future.

Let's commit these changes and start creating the database changes.

  > git add .
  > git commit -am 'Initialize Sqitch configuration.'
  [master 79fe2cc] Initialize Sqitch configuration.
   2 files changed, 19 insertions(+)
   create mode 100644 sqitch.conf
   create mode 100644 sqitch.plan

Our First Change

First, our app will need a database user, so let's create one. Run this command:

  > sqitch add appuser -n 'Creates a an application user.'
  Created deploy/appuser.sql
  Created revert/appuser.sql
  Created verify/appuser.sql
  Added "appuser" to sqitch.plan

The "add" command adds a database change to the plan and writes deploy, revert, and verify scripts that represent the change. Now we edit these files. The "deploy" script's job is to create the table. By default, the deploy/appuser.sql file looks like this:

  -- Deploy flipr:appuser to mysql

  BEGIN;

  -- XXX Add DDLs here.

  COMMIT;

What we want to do is to replace the "XXX" comment with the "CREATE USER" statement, like so:

  -- Deploy flipr:users to mysql

  BEGIN;

  CREATE USER flipr;

  COMMIT;

The "revert" script's job is to precisely revert the change to the deploy script, so we edit this to revert/appuser.sql to look like this:

  -- Revert flipr:users from mysql

  BEGIN;

  DROP USER flipr;

  COMMIT;

Now we can try deploying this change:

  > mysql -u root --execute 'CREATE DATABASE flipr_test'
  > sqitch deploy db:mysql://root@/flipr_test
  Deploying changes to db:mysql://root@/flipr_test
    + appuser .. ok

First Sqitch created the registry database and tables used to track database changes. The registry database is separate from the database to which the "appuser" change was deployed; by default, its name is "sqitch", and will be used to manage all projects on a single MySQL server. Ideally, only Sqitch data will be stored in this database, so it probably makes the most sense to create a superuser named "sqitch" or something similar and use it to deploy changes.

If you'd like it to use a different database as the registry database, use "sqitch engine add mysql $name" to configure it (or via the "target" command; more below). This will be useful if you don't want to use the same registry database to manage multiple databases on the same server.

Next, Sqitch deploys changes to the target database, which we specified on the command-line. We only have one change so far; the "+" reinforces the idea that the change is being added to the database.

With this change deployed, if you connect to the database, you'll be able to see the user:

  > mysql -u root --execute "SELECT user from mysql.user WHERE user = 'flipr';"
  +-------+
  | User  |
  +-------+
  | flipr |
  +-------+

Trust, But Verify

But that's too much work. do you really want to do something like that after every deploy?

Here's where the "verify" script comes in. Its job is to test that the deploy did was it was supposed to. It should do so without regard to any data that might be in the database, and should throw an error if the deploy was not successful. The simplest way to see if a user exists is to check the "mysql.user" table. However, throwing an error in the event that the user does not exist is tricky in MySQL. To simplify things, on MySQL 5.5.0 and higher, Sqitch provides a custom function you can use in your tests, "checkit()". It works kind of like a "CHECK" constraint in other databases: pass an expression as the first argument, and an error message as the second. If the expression evaluates to false, an exception will be thrown with the error message.

Give it a try. Put this query into verify/appuser.sql:

  SELECT sqitch.checkit(COUNT(*), 'User "flipr" does not exist')
    FROM mysql.user WHERE user = 'flipr';

This will work well as long as we know that the registry database is named "sqitch". If you've set "engine.mysql.registry" to a different value, you will need to make sure you specify the correct database name in the script.

Now you can run the "verify" script with the "verify" command:

  > sqitch verify db:mysql://root@/flipr_test
  Verifying flipr_test
    * appuser .. ok
  Verify successful

Looks good! If you want to make sure that the verify script correctly dies if the table doesn't exist, temporarily change the user name in the script to something that doesn't exist, something like:

  SELECT sqitch.checkit(COUNT(*), 'User "flipr" does not exist')
    FROM mysql.user WHERE user = 'nonesuch';

Then "verify" again:

  > sqitch verify db:mysql://root@/flipr_test
  Verifying db:mysql://root@/flipr_test
    * appuser .. ERROR 1644 (ERR0R) at line 5 in file: 'verify/appuser.sql': User "flipr" does not exist
  # Verify script "verify/appuser.sql" failed.
  not ok

  Verify Summary Report
  ---------------------
  Changes: 1
  Errors:  1
  Verify failed

The "checkit()" function is kind enough to use the error message to tell us what the problem is. Don't forget to change the table name back before continuing!

Status, Revert, Log, Repeat

For purely informational purposes, we can always see how a deployment was recorded via the "status" command, which reads the tables from the registry database:

  > sqitch status db:mysql://root@/flipr_test
  # On database db:mysql://root@/flipr_test
  # Project:  flipr
  # Change:   f56dd1a1ab029f398cec2cebb2ecc527fa0332c2
  # Name:     appuser
  # Deployed: 2013-12-31 13:13:17 -0800
  # By:       Marge N. OXVera <marge@example.com>
  # 
  Nothing to deploy (up-to-date)

Let's make sure that we can revert the change:

  > sqitch revert db:mysql://root@/flipr_test
  Revert all changes from db:mysql://root@/flipr_test? [Yes] 
    - appuser .. ok

The "revert" command first prompts to make sure that we really do want to revert. This is to prevent unnecessary accidents. You can pass the "-y" option to disable the prompt. Also, notice the "-" before the change name in the output, which reinforces that the change is being removed from the database. And now the schema should be gone:

  > mysql -u root --execute "SELECT user from mysql.user WHERE user = 'flipr';"

And the status message should reflect as much:

  > sqitch status db:mysql://root@/flipr_test
  # On database db:mysql://root@/flipr_test
  No changes deployed

Of course, since nothing is deployed, the "verify" command has nothing to verify:

  > sqitch verify db:mysql://root@/flipr_test
  Verifying db:mysql://root@/flipr_test
  No changes deployed

However, we still have a record that the change happened, visible via the "log" command:

  > sqitch log db:mysql://root@/flipr_test
  On database db:mysql://root@/flipr_test
  Revert f56dd1a1ab029f398cec2cebb2ecc527fa0332c2
  Name:      appuser
  Committer: Marge N. OXVera <marge@example.com>
  Date:      2013-12-31 13:26:39 -0800

      Creates a an application user.

  Deploy f56dd1a1ab029f398cec2cebb2ecc527fa0332c2
  Name:      appuser
  Committer: Marge N. OXVera <marge@example.com>
  Date:      2013-12-31 13:13:17 -0800

      Creates a an application user.

Note that the actions we took are shown in reverse chronological order, with the revert first and then the deploy.

Cool. Now let's commit it.

  > git add .
  > git commit -m 'Add the "flipr" user.'
  [master c63acb9] Add the "flipr" user.
   4 files changed, 23 insertions(+)
   create mode 100644 deploy/appuser.sql
   create mode 100644 revert/appuser.sql
   create mode 100644 verify/appuser.sql

And then deploy again. This time, let's use the "--verify" option, so that the "verify" script is applied when the change is deployed:

  > sqitch deploy --verify db:mysql://root@/flipr_test
  Deploying changes to db:mysql://root@/flipr_test
    + appuser .. ok

And now the "flipr" user should be back:

  > mysql -u root --execute "SELECT user from mysql.user WHERE user = 'flipr';"
  +-------+
  | user  |
  +-------+
  | flipr |
  +-------+

When we look at the status, the deployment will be there:

  > sqitch status db:mysql://root@/flipr_test
  # On database db:mysql://root@/flipr_test
  # Project:  flipr
  # Change:   f56dd1a1ab029f398cec2cebb2ecc527fa0332c2
  # Name:     appuser
  # Deployed: 2013-12-31 13:28:23 -0800
  # By:       Marge N. OXVera <marge@example.com>
  # 
  Nothing to deploy (up-to-date)

On Target

I'm getting a little tired of always having to type "db:mysql://root@/flipr_test", aren't you? This database connection URI <https://github.com/theory/uri-db/> tells Sqitch how to connect to the deployment target, but we don't have to keep using the URI. We can name the target:

  > sqitch target add flipr_test db:mysql://root@/flipr_test

The "target" command, inspired by "git-remote" <http://git-scm.com/docs/git-remote>, allows management of one or more named deployment targets. We've just added a target named "flipr_test", which means we can use the string "flipr_test" for the target, rather than the URI. But since we're doing so much testing, we can also tell Sqitch to deploy to the "flipr_test" target by default:

  > sqitch engine add mysql flipr_test

Now we can omit the target argument altogether, unless we need to deploy to another database. Which we will, eventually, but at least our examples will be simpler from here on in, e.g.:

  > sqitch status
  # On database flipr_test
  # Project:  flipr
  # Change:   f56dd1a1ab029f398cec2cebb2ecc527fa0332c2
  # Name:     appuser
  # Deployed: 2013-12-31 13:28:23 -0800
  # By:       Marge N. OXVera <marge@example.com>
  # 
  Nothing to deploy (up-to-date)

Yay, that allows things to be a little more concise. Let's also make sure that changes are verified after deploying them:

  > sqitch config --bool deploy.verify true
  > sqitch config --bool rebase.verify true

We'll see the "rebase" command a bit later. In the meantime, let's commit the new configuration and and make some more changes!

  > git commit -am 'Set default target and always verify.'
  [master c793050] Set default target and always verify.
   1 file changed, 8 insertions(+)

Deploy with Dependency

Let's add another change, this time to create a table. Our app will need users, of course, so we'll create a table for them. First, add the new change:

  > sqitch add users --requires appuser -n 'Creates table to track our users.'
  Created deploy/users.sql
  Created revert/users.sql
  Created verify/users.sql
  Added "users [appuser]" to sqitch.plan

Note that we're requiring the "appuser" change as a dependency of the new "users" change. Although that change has already been added to the plan and therefore should always be applied before the "users" change, it's a good idea to be explicit about dependencies.

Now edit the scripts. When you're done, deploy/users.sql should look like this:

  -- Deploy flipr:users to mysql
  -- requires: appuser

  BEGIN;

  CREATE TABLE users (
      nickname  VARCHAR(512) PRIMARY KEY,
      password  VARCHAR(512) NOT NULL,
      timestamp DATETIME(6)  NOT NULL
  );

  GRANT SELECT ON TABLE users TO flipr;

  COMMIT;

A few things to notice here. On the second line, the dependence on the "appuser" change has been listed. This doesn't do anything, but the default MySQL "deploy" template lists it here for your reference while editing the file. Useful, right?

The "flipr" user has been granted "SELECT" access to the table. The app needs to read the data, right? This is why we need to require the "appuser" change.

Now for the verify script. The simplest way to check that the table was created and has the expected columns without touching the data? Just select from the table with a false "WHERE" clause. Add this to verify/users.sql:

  SELECT nickname, password, timestamp
    FROM users
   WHERE 0;

Now for the revert script: all we have to do is drop the table. Add this to revert/users.sql:

  DROP TABLE users;

Couldn't be much simpler, right? Let's deploy this bad boy:

  > sqitch deploy
  Deploying changes to flipr_test
    + users .. ok

We know, since verification is enabled, that the table must have been created. But for the purposes of visibility, let's have a quick look:

  > mysql -u root -D flipr_test --execute 'SHOW TABLES'
  +----------------------+
  | Tables_in_flipr_test |
  +----------------------+
  | users                |
  +----------------------+

We can also verify all currently deployed changes with the "verify" command:

  > sqitch verify
  Verifying flipr_test
    * appuser .. ok
    * users .... ok
  Verify successful

Now have a look at the status:

  > sqitch status
  # On database flipr_test
  # Project:  flipr
  # Change:   2bd1190fdb324c2609f0c7f0cef73d8cb434ba0e
  # Name:     users
  # Deployed: 2013-12-31 13:34:25 -0800
  # By:       Marge N. OXVera <marge@example.com>
  # 
  Nothing to deploy (up-to-date)

Success! Let's make sure we can revert the change, as well:

  > sqitch revert --to @HEAD^ -y
  Reverting changes to appuser from flipr_test
    - users .. ok

Note that we've used the "--to" option to specify the change to revert to. And what do we revert to? The symbolic tag @HEAD, when passed to "revert", always refers to the last change deployed to the database. (For other commands, it refers to the last change in the plan.) Appending the caret ("^") tells Sqitch to select the change prior to the last deployed change. So we revert to "appuser", the penultimate change. The other potentially useful symbolic tag is @ROOT, which refers to the first change deployed to the database (or in the plan, depending on the command).

Back to the database. The "users" table should be gone but the "flipr" user should still be around:

  > mysql -u root -D flipr_test --execute 'SHOW TABLES'
  > mysql -u root --execute "SELECT user from mysql.user WHERE user = 'flipr';"
  +-------+
  | User  |
  +-------+
  | flipr |
  +-------+

The "status" command politely informs us that we have undeployed changes:

  > sqitch status
  # On database flipr_test
  # Project:  flipr
  # Change:   f56dd1a1ab029f398cec2cebb2ecc527fa0332c2
  # Name:     appuser
  # Deployed: 2013-12-31 13:28:23 -0800
  # By:       Marge N. OXVera <marge@example.com>
  # 
  Undeployed change:
    * users

As does the "verify" command:

  > sqitch verify
  Verifying flipr_test
    * appuser .. ok
  Undeployed change:
    * users
  Verify successful

Note that the verify is successful, because all currently-deployed changes are verified. The list of undeployed changes (just "users" here) reminds us about the current state.

Okay, let's commit and deploy again:

  > git add .
  > git commit -am 'Add users table.'
  [master 7c99fb0] Add users table.
   4 files changed, 31 insertions(+)
   create mode 100644 deploy/users.sql
   create mode 100644 revert/users.sql
   create mode 100644 verify/users.sql
  > sqitch deploy
  Deploying changes to flipr_test
    + users .. ok

Looks good. Check the status:

  > sqitch status
  # On database flipr_test
  # Project:  flipr
  # Change:   2bd1190fdb324c2609f0c7f0cef73d8cb434ba0e
  # Name:     users
  # Deployed: 2013-12-31 13:37:02 -0800
  # By:       Marge N. OXVera <marge@example.com>
  # 
  Nothing to deploy (up-to-date)

Excellent. Let's do some more!

Add Two at Once

Let's add a couple more changes to add functions for managing users.

  > sqitch add insert_user --requires users --requires appuser \
    -n 'Creates a function to insert a user.'
  Created deploy/insert_user.sql
  Created revert/insert_user.sql
  Created verify/insert_user.sql
  Added "insert_user [users appuser]" to sqitch.plan

  > sqitch add change_pass --requires users --requires appuser \
    -n 'Creates a function to change a user password.'
  Created deploy/change_pass.sql
  Created revert/change_pass.sql
  Created verify/change_pass.sql
  Added "change_pass [users appuser]" to sqitch.plan

Now might be a good time to have a look at the deployment plan:

  > cat sqitch.plan
  %syntax-version=1.0.0
  %project=flipr
  %uri=https://github.com/theory/sqitch-mysql-intro/

  appuser 2013-12-31T21:04:04Z Marge N. OXVera <marge@example.com> # Creates a an application user.
  users [appuser] 2013-12-31T21:32:48Z Marge N. OXVera <marge@example.com> # Creates table to track our users.
  insert_user [users appuser] 2013-12-31T21:37:29Z Marge N. OXVera <marge@example.com> # Creates a function to insert a user.
  change_pass [users appuser] 2013-12-31T21:37:36Z Marge N. OXVera <marge@example.com> # Creates a function to change a user password.

Each change appears on a single line with the name of the change, a bracketed list of dependencies, a timestamp, the name and email address of the user who planned the change, and a note.

Let's write the code for the new changes. Here's what deploy/insert_user.sql should look like:

  -- Deploy flipr:insert_user to mysql
  -- requires: users
  -- requires: appuser

  BEGIN;

  DELIMITER //

  CREATE PROCEDURE insert_user(
      nickname VARCHAR(512),
      password VARCHAR(512)
  ) SQL SECURITY DEFINER
  BEGIN
      INSERT INTO users (nickname, password, timestamp)
      VALUES (nickname, md5(password), UTC_TIMESTAMP(6));
  END
  //

  DELIMITER ;

  GRANT EXECUTE ON PROCEDURE insert_user to flipr;

  COMMIT;

Here's what verify/insert_user.sql might look like, using the Sqitch "checkit()" function again:

  -- Verify flipr:insert_user on mysql

  BEGIN;

  SELECT sqitch.checkit(COUNT(*), 'Procedure "insert_user" does not exist')
    FROM mysql.proc
   WHERE db = database()
     AND specific_name = 'insert_user';

  ROLLBACK;

We simply take advantage of the fact that the new procedure should be listed in the "mysql.proc" table and throw an exception if it does not exist.

And revert/insert_user.sql should look something like this:

  -- Revert flipr:insert_user from mysql
  BEGIN;
  DROP PROCEDURE insert_user;
  COMMIT;

Now for "change_pass"; deploy/change_pass.sql might look like this:

  -- Deploy flipr:change_pass to mysql
  -- requires: users
  -- requires: appuser

  BEGIN;

  DELIMITER //

  CREATE FUNCTION change_pass(
      nickname VARCHAR(512),
      oldpass  VARCHAR(512),
      newpass  VARCHAR(512)
  ) RETURNS INTEGER SQL SECURITY DEFINER
  BEGIN
      UPDATE users
         SET password = md5(newpass)
       WHERE nickname = nickname
         AND password = md5(oldpass);
      RETURN ROW_COUNT();
  END;
  //

  DELIMITER ;

  GRANT EXECUTE ON FUNCTION change_pass to flipr;

  COMMIT;

Use "checkit()" in verify/change_pass.sql again:

  BEGIN;
  SELECT sqitch.checkit(COUNT(*), 'Procedure "change_pass" does not exist')
    FROM mysql.proc
   WHERE db = database()
     AND specific_name = 'change_pass';
  COMMIT;

And of course, its "revert" script, revert/change_pass.sql, should look something like:

  -- Revert flipr:change_pass from mysql
  BEGIN;
  DROP FUNCTION change_pass;
  COMMIT;

Try em out!

  > sqitch deploy
  Deploying changes to flipr_test
    + insert_user .. ok
    + change_pass .. ok

Do we have the functions? Of course we do, they were verified. Still, have a look:

  > mysql -u root --execute "SELECT name FROM mysql.proc WHERE db = 'flipr_test'"
  +-------------+
  | name        |
  +-------------+
  | change_pass |
  | insert_user |
  +-------------+

And what's the status?

  > sqitch status
  # On database flipr_test
  # Project:  flipr
  # Change:   b0a598b91ce97cf1b95ded97a6452bf03231a2cd
  # Name:     change_pass
  # Deployed: 2013-12-31 13:39:49 -0800
  # By:       Marge N. OXVera <marge@example.com>
  # 
  Nothing to deploy (up-to-date)

Looks good. Let's make sure revert works:

  > sqitch revert -y --to @HEAD^^
  Reverting changes to users from flipr_test
    - change_pass .. ok
    - insert_user .. ok
  > mysql -u root --execute "SELECT name FROM mysql.proc WHERE db = 'flipr_test'"

Note the use of "@HEAD^^" to specify that the revert be to two changes prior the last deployed change. Looks good. Let's do the commit and re-deploy dance:

  > git add .
  > git commit -m 'Add `insert_user()` and `change_pass()`.'
  [master 0f95e13] Add `insert_user()` and `change_pass()`.
   7 files changed, 86 insertions(+)
   create mode 100644 deploy/change_pass.sql
   create mode 100644 deploy/insert_user.sql
   create mode 100644 revert/change_pass.sql
   create mode 100644 revert/insert_user.sql
   create mode 100644 verify/change_pass.sql
   create mode 100644 verify/insert_user.sql

  > sqitch deploy
  Deploying changes to flipr_test
    + insert_user .. ok
    + change_pass .. ok

  > sqitch status
  # On database flipr_test
  # Project:  flipr
  # Change:   b0a598b91ce97cf1b95ded97a6452bf03231a2cd
  # Name:     change_pass
  # Deployed: 2013-12-31 13:40:40 -0800
  # By:       Marge N. OXVera <marge@example.com>
  # 
  Nothing to deploy (up-to-date)

  > sqitch verify
  Verifying flipr_test
    * appuser ...... ok
    * users ........ ok
    * insert_user .. ok
    * change_pass .. ok
  Verify successful

Great, we're fully up-to-date!

Ship It!

Let's do a first release of our app. Let's call it "1.0.0-dev1" Since we want to have it go out with deployments tied to the release, let's tag it:

  > sqitch tag v1.0.0-dev1 -n 'Tag v1.0.0-dev1.'
  Tagged "change_pass" with @v1.0.0-dev1
  > git commit -am 'Tag the database with v1.0.0-dev1.'
  [master 0595297] Tag the database with v1.0.0-dev1.
   1 file changed, 1 insertion(+)
  > git tag v1.0.0-dev1 -am 'Tag v1.0.0-dev1'

Now let's bundle everything up for release:

  > sqitch bundle
  Bundling into bundle/
  Writing config
  Writing plan
  Writing scripts
    + appuser
    + users
    + insert_user
    + change_pass @v1.0.0-dev1

Now we can package the bundle directory and distribute it. When it gets installed somewhere, users can use Sqitch to deploy to the database. We ought to try deploying it, but first we'll need to revert our existing databases, as a single Sqitch project cannot be deployed to two databases on the same server unless it uses a different registry database and the "checkit()" function is not used in verify scripts. We have used "checkit()" quite a bit, so we need to keep the Sqitch database name just where it is. Fortunately, it's easy to build the database again, so let's just revert it.

  > sqitch revert -y
  Reverting all changes from flipr_test
    - change_pass .. ok
    - insert_user .. ok
    - users ........ ok
    - appuser ...... ok

Now we can try deploying the bundle:

  > cd bundle
  > mysql -u root --execute 'CREATE DATABASE flipr_dev'
  > sqitch deploy db:mysql://root@/flipr_dev
  Deploying changes to db:mysql://root@/flipr_dev
    + appuser ................... ok
    + users ..................... ok
    + insert_user ............... ok
    + change_pass @v1.0.0-dev1 .. ok

Great, all four changes were deployed and "change_pass" was tagged with "@v1.0.0-dev1". Let's have a look at the status:

  > sqitch status db:mysql://root@/flipr_dev
  # On database db:mysql://root@/flipr_dev
  # Project:  flipr
  # Change:   b0a598b91ce97cf1b95ded97a6452bf03231a2cd
  # Name:     change_pass
  # Tag:      @v1.0.0-dev1
  # Deployed: 2013-12-31 13:44:04 -0800
  # By:       Marge N. OXVera <marge@example.com>
  # 
  Nothing to deploy (up-to-date)

Looks good, eh? Go ahead and revert it:

  > sqitch revert -y db:mysql://root@/flipr_dev
  Reverting all changes from db:mysql://root@/flipr_dev
    - change_pass @v1.0.0-dev1 .. ok
    - insert_user ............... ok
    - users ..................... ok
    - appuser ................... ok

Now package it up and ship it!

Flip Out

Now that we've got the basics of user management done, let's get to work on the core of our product, the "flip." Since other folks are working on other tasks in the repository, we'll work on a branch, so we can all stay out of each other's way. So let's branch:

  > git checkout -b flips
  Switched to a new branch 'flips'

Now we can add a new change to create a table for our flips.

  > sqitch add flips -r appuser -r users -n 'Adds table for storing flips.'
  Created deploy/flips.sql
  Created revert/flips.sql
  Created verify/flips.sql
  Added "flips [appuser users]" to sqitch.plan

You know the drill by now. Edit deploy/flips.sql:

  -- Deploy flipr:flips to mysql
  -- requires: appuser
  -- requires: users

  BEGIN;

  CREATE TABLE flips (
      id        BIGINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
      nickname  VARCHAR(512) NOT NULL REFERENCES users(nickname),
      body      VARCHAR(180) NOT NULL,
      timestamp DATETIME(6)  NOT NULL
  );

  GRANT SELECT ON TABLE flips TO flipr;

  COMMIT;

Edit verify/flips.sql:

  -- Verify flipr:flips on mysql

  BEGIN;

  SELECT id
       , nickname
       , body
       , timestamp
    FROM flipr.flips
   WHERE 0;

  COMMIT;

And edit revert/flips.sql:

  -- Revert flipr:flips from mysql

  BEGIN;

  DROP TABLE flips;

  COMMIT;

And give it a whirl:

  > sqitch deploy
  Deploying changes to flipr_test
    + appuser ................... ok
    + users ..................... ok
    + insert_user ............... ok
    + change_pass @v1.0.0-dev1 .. ok

Look good?

  > sqitch status --show-tags
  # On database flipr_test
  # Project:  flipr
  # Change:   b3ccd37da58ac232c23edfa0adaf2d6f483842fd
  # Name:     flips
  # Deployed: 2013-12-31 13:55:04 -0800
  # By:       Marge N. OXVera <marge@example.com>
  # 
  # Tag:
  #   @v1.0.0-dev1 - 2013-12-31 13:55:04 -0800 - Marge N. OXVera <marge@example.com>
  # 
  Nothing to deploy (up-to-date)

Note the use of "--show tags" to show all the deployed tags. Now make it so:

  > git add .
  > git commit -am 'Add flips table.'
  [flips ce1b53d] Add flips table.
   4 files changed, 37 insertions(+)
   create mode 100644 deploy/flips.sql
   create mode 100644 revert/flips.sql
   create mode 100644 verify/flips.sql

Wash, Rinse, Repeat

Now comes the time to add functions to manage flips. I'm sure you have things nailed down now. Go ahead and add "insert_flip" and "delete_flip" changes and commit them. The "insert_flip" deploy script might look something like:

  -- Deploy flipr:insert_flip to mysql
  -- requires: flips
  -- requires: appuser

  BEGIN;

  DELIMITER //

  CREATE FUNCTION insert_flip(
      nickname VARCHAR(512),
      body     VARCHAR(180)
  ) RETURNS BIGINT SQL SECURITY DEFINER
  BEGIN
      INSERT INTO flips (nickname, body)
      VALUES (nickname, body);
      RETURN LAST_INSERT_ID();
  END;
  //

  DELIMITER ;

  GRANT EXECUTE ON FUNCTION insert_flip to flipr;

  COMMIT;

And the "delete_flip" deploy script might look something like:

  -- Deploy flipr:delete_flip to mysql
  -- requires: flips
  -- requires: appuser

  BEGIN;

  DELIMITER //

  CREATE FUNCTION delete_flip(
      flip_id BIGINT
  ) RETURNS INTEGER SQL SECURITY DEFINER
  BEGIN
      DELETE FROM flips WHERE id = flip_id;
      RETURN ROW_COUNT();
  END;
  //

  DELIMITER ;

  GRANT EXECUTE ON FUNCTION delete_flip to flipr;

  COMMIT;

The "verify" scripts are:

  -- Verify flipr:insert_flip on mysql

  BEGIN;

  SELECT sqitch.checkit(COUNT(*), 'Function "insert_flip" does not exist')
    FROM mysql.proc
   WHERE db = database()
     AND specific_name = 'insert_flip';

  ROLLBACK;

And:

  -- Verify flipr:delete_flip on mysql

  BEGIN;

  SELECT sqitch.checkit(COUNT(*), 'Function "delete_flip" does not exist')
    FROM mysql.proc
   WHERE db = database()
     AND specific_name = 'delete_flip';

  ROLLBACK;

The "revert" scripts are:

  -- Revert flipr:insert_flip from mysql

  BEGIN;

  DROP FUNCTION insert_flip;

  COMMIT;

And:

  -- Revert flipr:delete_flip from mysql

  BEGIN;

  DROP FUNCTION delete_flip;

  COMMIT;

Check the example git repository <https://github.com/theory/sqitch-intro> for the complete details. Test "deploy" and "revert", then commit it to the repository. The status should end up looking something like this:

  > sqitch status --show-tags
  # On database flipr_test
  # Project:  flipr
  # Change:   7bf30e6b7b0a4e61f30dd4148f5b837bdddae086
  # Name:     delete_flip
  # Deployed: 2013-12-31 13:58:54 -0800
  # By:       Marge N. OXVera <marge@example.com>
  # 
  # Tag:
  #   @v1.0.0-dev1 - 2013-12-31 13:55:04 -0800 - Marge N. OXVera <marge@example.com>
  # 
  Nothing to deploy (up-to-date)

Good, we've finished this feature. Time to merge back into "master".

Emergency

Let's do it:

  > git checkout master
  Switched to branch 'master'
  > git pull
  Updating 0595297..5a58089
  Fast-forward
   deploy/delete_list.sql | 22 ++++++++++++++++++++++
   deploy/insert_list.sql | 25 +++++++++++++++++++++++++
   deploy/lists.sql       | 17 +++++++++++++++++
   revert/delete_list.sql |  7 +++++++
   revert/insert_list.sql |  7 +++++++
   revert/lists.sql       |  7 +++++++
   sqitch.plan            |  4 ++++
   verify/delete_list.sql | 10 ++++++++++
   verify/insert_list.sql | 10 ++++++++++
   verify/lists.sql       |  8 ++++++++
   10 files changed, 117 insertions(+)
   create mode 100644 deploy/delete_list.sql
   create mode 100644 deploy/insert_list.sql
   create mode 100644 deploy/lists.sql
   create mode 100644 revert/delete_list.sql
   create mode 100644 revert/insert_list.sql
   create mode 100644 revert/lists.sql
   create mode 100644 verify/delete_list.sql
   create mode 100644 verify/insert_list.sql
   create mode 100644 verify/lists.sql

Hrm, that's interesting. Looks like someone made some changes to "master". They added list support. Well, let's see what happens when we merge our changes.

  > git merge --no-ff flips
  Auto-merging sqitch.plan
  CONFLICT (content): Merge conflict in sqitch.plan
  Automatic merge failed; fix conflicts and then commit the result.

Oh, a conflict in sqitch.plan. Not too surprising, since both the merged "lists" branch and our "flips" branch added changes to the plan. Let's try a different approach.

The truth is, we got lazy. Those changes when we pulled master from the origin should have raised a red flag. It's considered a bad practice not to look at what's changed in "master" before merging in a branch. What one should do is either:

Rebase the flips branch from master before merging. This "rewinds" the branch changes, pulls from "master", and then replays the changes back on top of the pulled changes.
Create a patch and apply that to master. This is the sort of thing you might have to do if you're sending changes to another user, especially if the VCS is not Git.

So let's restore things to how they were at master:

  > git reset --hard HEAD
  HEAD is now at 5a58089 Merge branch 'lists'

That throws out our botched merge. Now let's go back to our branch and rebase it on "master":

  > git checkout flips
  Switched to branch 'flips'
  > git rebase master
  First, rewinding head to replay your work on top of it...
  Applying: Add flips table.
  Using index info to reconstruct a base tree...
  M     sqitch.plan
  Falling back to patching base and 3-way merge...
  Auto-merging sqitch.plan
  CONFLICT (content): Merge conflict in sqitch.plan
  Failed to merge in the changes.
  Patch failed at 0001 Add flips table.
  The copy of the patch that failed is found in:
     .git/rebase-apply/patch

  When you have resolved this problem, run "git rebase --continue".
  If you prefer to skip this patch, run "git rebase --skip" instead.
  To check out the original branch and stop rebasing, run "git rebase --abort".

Oy, that's kind of a pain. It seems like no matter what we do, we'll need to resolve conflicts in that file. Except in Git. Fortunately for us, we can tell Git to resolve conflicts in sqitch.plan differently. Because we only ever append lines to the file, we can have it use the "union" merge driver, which, according to its docs <http://git-scm.com/docs/gitattributes#_built-in_merge_drivers>:

Run 3-way file level merge for text files, but take lines from both versions, instead of leaving conflict markers. This tends to leave the added lines in the resulting file in random order and the user should verify the result. Do not use this if you do not understand the implications.

This has the effect of appending lines from all the merging files, which is exactly what we need. So let's give it a try. First, back out the botched rebase:

  > git rebase --abort

Now add the union merge driver to .gitattributes for sqitch.plan and rebase again:

  > echo sqitch.plan merge=union > .gitattributes
  > git rebase master
  First, rewinding head to replay your work on top of it...
  Applying: Add flips table.
  Using index info to reconstruct a base tree...
  M     sqitch.plan
  Falling back to patching base and 3-way merge...
  Auto-merging sqitch.plan
  Applying: Add functions to insert and delete flips.
  Using index info to reconstruct a base tree...
  M     sqitch.plan
  Falling back to patching base and 3-way merge...
  Auto-merging sqitch.plan

Ah, that looks a bit better. Let's have a look at the plan:

  > cat sqitch.plan
  %syntax-version=1.0.0
  %project=flipr
  %uri=https://github.com/theory/sqitch-mysql-intro/

  appuser 2013-12-31T21:04:04Z Marge N. OXVera <marge@example.com> # Creates a an application user.
  users [appuser] 2013-12-31T21:32:48Z Marge N. OXVera <marge@example.com> # Creates table to track our users.
  insert_user [users appuser] 2013-12-31T21:37:29Z Marge N. OXVera <marge@example.com> # Creates a function to insert a user.
  change_pass [users appuser] 2013-12-31T21:37:36Z Marge N. OXVera <marge@example.com> # Creates a function to change a user password.
  @v1.0.0-dev1 2013-12-31T21:41:08Z Marge N. OXVera <marge@example.com> # Tag v1.0.0-dev1.

  lists [appuser users] 2013-12-31T21:46:22Z Marge N. OXVera <marge@example.com> # Adds table for storing lists.
  insert_list [lists appuser] 2013-12-31T21:48:14Z Marge N. OXVera <marge@example.com> # Creates a function to insert a list.
  delete_list [lists appuser] 2013-12-31T21:49:41Z Marge N. OXVera <marge@example.com> # Creates a function to insert a list.
  flips [appuser users] 2013-12-31T21:53:03Z Marge N. OXVera <marge@example.com> # Adds table for storing flips.
  insert_flip [flips appuser] 2013-12-31T21:56:12Z Marge N. OXVera <marge@example.com> # Creates a function to insert a flip.
  delete_flip [flips appuser] 2013-12-31T21:56:22Z Marge N. OXVera <marge@example.com> # Creates a function to delete a flip.

Note that it has appended the changes from the merged "lists" branch, and then merged the changes from our "flips" branch. Test it to make sure it works as expected:

  > sqitch rebase -y
  Reverting all changes from flipr_test
    - delete_flip ............... ok
    - insert_flip ............... ok
    - flips ..................... ok
    - change_pass @v1.0.0-dev1 .. ok
    - insert_user ............... ok
    - users ..................... ok
    - appuser ................... ok
  Deploying changes to flipr_test
    + appuser ................... ok
    + users ..................... ok
    + insert_user ............... ok
    + change_pass @v1.0.0-dev1 .. ok
    + lists ..................... ok
    + insert_list ............... ok
    + delete_list ............... ok
    + flips ..................... ok
    + insert_flip ............... ok
    + delete_flip ............... ok

Note the use of "rebase", which combines a "revert" and a "deploy" into a single command. Handy, right? It correctly reverted our changes, and then deployed them all again in the proper order. So let's commit .gitattributes; seems worthwhile to keep that change:

  > git add .
  > git commit -m 'Add `.gitattributes` with union merge for `sqitch.plan`.'
  [flips d813f7c] Add `.gitattributes` with union merge for `sqitch.plan`.
   1 file changed, 1 insertion(+)
   create mode 100644 .gitattributes

Merges Mastered

And now, finally, we can merge into "master":

  > git checkout master
  Switched to branch 'master'
  > git merge --no-ff flips -m "Merge branch 'flips'"
  Merge made by the 'recursive' strategy.
   .gitattributes         |  1 +
   deploy/delete_flip.sql | 22 ++++++++++++++++++++++
   deploy/flips.sql       | 16 ++++++++++++++++
   deploy/insert_flip.sql | 24 ++++++++++++++++++++++++
   revert/delete_flip.sql |  7 +++++++
   revert/flips.sql       |  7 +++++++
   revert/insert_flip.sql |  7 +++++++
   sqitch.plan            |  3 +++
   verify/delete_flip.sql | 10 ++++++++++
   verify/flips.sql       | 12 ++++++++++++
   verify/insert_flip.sql | 10 ++++++++++
   11 files changed, 119 insertions(+)
   create mode 100644 .gitattributes
   create mode 100644 deploy/delete_flip.sql
   create mode 100644 deploy/flips.sql
   create mode 100644 deploy/insert_flip.sql
   create mode 100644 revert/delete_flip.sql
   create mode 100644 revert/flips.sql
   create mode 100644 revert/insert_flip.sql
   create mode 100644 verify/delete_flip.sql
   create mode 100644 verify/flips.sql
   create mode 100644 verify/insert_flip.sql

And double-check our work:

  > cat sqitch.plan
  %syntax-version=1.0.0
  %project=flipr
  %uri=https://github.com/theory/sqitch-mysql-intro/

  appuser 2013-12-31T21:04:04Z Marge N. OXVera <marge@example.com> # Creates a an application user.
  users [appuser] 2013-12-31T21:32:48Z Marge N. OXVera <marge@example.com> # Creates table to track our users.
  insert_user [users appuser] 2013-12-31T21:37:29Z Marge N. OXVera <marge@example.com> # Creates a function to insert a user.
  change_pass [users appuser] 2013-12-31T21:37:36Z Marge N. OXVera <marge@example.com> # Creates a function to change a user password.
  @v1.0.0-dev1 2013-12-31T21:41:08Z Marge N. OXVera <marge@example.com> # Tag v1.0.0-dev1.

  lists [appuser users] 2013-12-31T21:46:22Z Marge N. OXVera <marge@example.com> # Adds table for storing lists.
  insert_list [lists appuser] 2013-12-31T21:48:14Z Marge N. OXVera <marge@example.com> # Creates a function to insert a list.
  delete_list [lists appuser] 2013-12-31T21:49:41Z Marge N. OXVera <marge@example.com> # Creates a function to insert a list.
  flips [appuser users] 2013-12-31T21:53:03Z Marge N. OXVera <marge@example.com> # Adds table for storing flips.
  insert_flip [flips appuser] 2013-12-31T21:56:12Z Marge N. OXVera <marge@example.com> # Creates a function to insert a flip.
  delete_flip [flips appuser] 2013-12-31T21:56:22Z Marge N. OXVera <marge@example.com> # Creates a function to delete a flip.

Much much better, a nice clean master now. And because it is now identical to the "flips" branch, we can just carry on. Go ahead and tag it, bundle, and release:

  > sqitch tag v1.0.0-dev2 -n 'Tag v1.0.0-dev2.'
  Tagged "delete_flip" with @v1.0.0-dev2
  > git commit -am 'Tag the database with v1.0.0-dev2.'
  [master 76d6e15] Tag the database with v1.0.0-dev2.
   1 file changed, 1 insertion(+)
  > git tag v1.0.0-dev2 -am 'Tag v1.0.0-dev2'
  > sqitch bundle --dest-dir flipr-1.0.0-dev2
  Bundling into flipr-1.0.0-dev2
  Writing config
  Writing plan
  Writing scripts
    + appuser
    + users
    + insert_user
    + change_pass @v1.0.0-dev1
    + lists
    + insert_list
    + delete_list
    + flips
    + insert_flip
    + delete_flip @v1.0.0-dev2

Note the use of the "--dest-dir" option to "sqitch bundle". Just a nicer way to create the top-level directory name so we don't have to rename it from bundle.

In Place Changes

Uh-oh, someone just noticed that MD5 hashing is not particularly secure. Why? Have a look at this:

  > mysql -u root -D flipr_test --execute "
      CALL insert_user('foo', 'secr3t');
      CALL insert_user('bar', 'secr3t');
      SELECT * FROM users;
  "
  +----------+----------------------------------+----------------------------+
  | nickname | password                         | timestamp                  |
  +----------+----------------------------------+----------------------------+
  | bar      | 9695da4dd567a19f9b92065f240c6725 | 2013-12-31 22:06:28.359118 |
  | foo      | 9695da4dd567a19f9b92065f240c6725 | 2013-12-31 22:06:28.358789 |
  +----------+----------------------------------+----------------------------+

If user "foo" ever got access to the database, she could quickly discover that user "bar" has the same password and thus be able to exploit the account. Not a great idea. So we need to modify the "insert_user()" and "change_pass()" functions to fix that. How?

We can use MySQL's "ENCRYPT()" <https://dev.mysql.com/doc/refman/5.5/en/encryption-functions.html#function_encrypt> function to encrypt passwords with a salt, so that they're all unique. But how to deploy the changes to "insert_user()" and "change_pass()"?

Normally, modifying functions in database changes is a PITA <http://www.urbandictionary.com/define.php?term=pita>. You have to make changes like these:

1.: Copy deploy/insert_user.sql to deploy/insert_user_encrypt.sql.
2.: Edit deploy/insert_user_encrypt.sql to switch from "MD5()" to "ENCRYPT()".
3.: Copy deploy/insert_user.sql to revert/insert_user_encrypt.sql. Yes, copy the original change script to the new revert change.
4.: Copy verify/insert_user.sql to verify/insert_user_encrypt.sql.
5.: Edit verify/insert_user_encrypt.sql to test that the function now properly uses "ENCRYPT()".
6.: Test the changes to make sure you can deploy and revert the "insert_user_encrypt" change.
7.: Now do the same for the "change_pass" scripts.

But you can have Sqitch do it for you. The only requirement is that a tag appear between the two instances of a change we want to modify. In general, you're going to make a change like this after a release, which you've tagged anyway, right? Well we have, with "@v1.0.0-dev2" added in the previous section. With that, we can let Sqitch do most of the hard work for us, thanks to the "rework" command, which is similar to "add":

  > sqitch rework insert_user -n 'Change insert_user to use encyrpt().'
  Added "insert_user [insert_user@v1.0.0-dev2]" to sqitch.plan.
  Modify these files as appropriate:
    * deploy/insert_user.sql
    * revert/insert_user.sql
    * verify/insert_user.sql

Oh, so we can edit those files in place. Nice! How does Sqitch do it? Well, in point of fact, it has copied the files to stand in for the previous instance of the "insert_user" change, which we can see via "git status":

  > git status
  # On branch master
  # Your branch is ahead of 'origin/master' by 5 commits.
  #   (use "git push" to publish your local commits)
  #
  # Changes not staged for commit:
  #   (use "git add <file>..." to update what will be committed)
  #   (use "git checkout -- <file>..." to discard changes in working directory)
  #
  #     modified:   revert/insert_user.sql
  #     modified:   sqitch.plan
  #
  # Untracked files:
  #   (use "git add <file>..." to include in what will be committed)
  #
  #     deploy/insert_user@v1.0.0-dev2.sql
  #     revert/insert_user@v1.0.0-dev2.sql
  #     verify/insert_user@v1.0.0-dev2.sql
  no changes added to commit (use "git add" and/or "git commit -a")

The "untracked files" part of the output is the first thing to notice. They are all named "insert_user@v1.0.0-dev2.sql". What that means is: "the "insert_user" change as it was implemented as of the "@v1.0.0-dev2" tag." These are copies of the original scripts, and thereafter Sqitch will find them when it needs to run scripts for the first instance of the "insert_user" change. As such, it's important not to change them again. But hey, if you're reworking the change, you shouldn't need to.

The other thing to notice is that revert/insert_user.sql has changed. Sqitch replaced it with the original deploy script. As of now, deploy/insert_user.sql and revert/insert_user.sql are identical. This is on the assumption that the deploy script will be changed (we're reworking it, remember?), and that the revert script should actually change things back to how they were before. Of course, the original deploy script may not be idempotent <http://en.wikipedia.org/wiki/Idempotence> -- that is, able to be applied multiple times without changing the result beyond the initial application. If it's not, you will likely need to modify it so that it properly restores things to how they were after the original deploy script was deployed. Or, more simply, it should revert changes back to how they were as-of the deployment of deploy/insert_user@v1.0.0-dev2.sql.

Had MySQL supported an "OR REPLACE" expression on "CREATE FUNCTION" and we had used it, our function deploy scripts would already idempotent. No matter how many times they were run, the end results would be the same instance of the function, with no duplicates or errors.

Alas, such is not the case for MySQL, so we will have to modify the scripts to drop the function before re-creating it. So let's do it. We'll modify the scripts drop and re-create the functions with to use "ENCRYPT()". Make this change to deploy/insert_user.sql:

  @@ -6,13 +6,14 @@ BEGIN;
 
   DELIMITER //
 
  +DROP PROCEDURE insert_user;
   CREATE PROCEDURE insert_user(
       nickname VARCHAR(512),
       password VARCHAR(512)
   ) SQL SECURITY DEFINER
   BEGIN
       INSERT INTO users (nickname, password, timestamp)
  -    VALUES (nickname, md5(password), UTC_TIMESTAMP(6));
  +    VALUES (nickname, ENCRYPT(md5(password), md5(FLOOR(RAND() * 0xFFFFFFFF))), UTC_TIMESTAMP(6));
   END
   //

We just need to add the "DROP" statement to the revert script, revert/insert_user.sql:

  @@ -6,6 +6,7 @@ BEGIN;
 
   DELIMITER //
 
  +DROP PROCEDURE insert_user;
   CREATE PROCEDURE insert_user(
       nickname VARCHAR(512),
       password VARCHAR(512)

Go ahead and rework the "change_pass" change, too:

  > sqitch rework change_pass -n 'Change change_pass to use encyrpt().'
  Added "change_pass [change_pass@v1.0.0-dev2]" to sqitch.plan.
  Modify these files as appropriate:
    * deploy/change_pass.sql
    * revert/change_pass.sql
    * verify/change_pass.sql

And make this change to deploy/change_pass.sql:

  @@ -6,6 +6,7 @@ BEGIN;
 
   DELIMITER //
 
  +DROP FUNCTION change_pass;
   CREATE FUNCTION change_pass(
       nickname VARCHAR(512),
       oldpass  VARCHAR(512),
  @@ -13,9 +14,9 @@ CREATE FUNCTION change_pass(
   ) RETURNS INTEGER SQL SECURITY DEFINER
   BEGIN
       UPDATE users
  -       SET password = md5(newpass)
  +       SET password = ENCRYPT(md5(newpass), md5(FLOOR(RAND() * 0xFFFFFFFF)))
        WHERE nickname = nickname
  -       AND password = md5(oldpass);
  +       AND password = ENCRYPT(md5(oldpass), password);
       RETURN ROW_COUNT();
   END;
   //

And add the "DROP FUNCTION" statement to its revert script, too:

  @@ -6,6 +6,7 @@ BEGIN;
 
   DELIMITER //
 
  +DROP FUNCTION change_pass;
   CREATE FUNCTION change_pass(
       nickname VARCHAR(512),
       oldpass  VARCHAR(512),

And now we're ready to try a deployment:

  >     sqitch deploy
  Deploying changes to flipr_test
    + insert_user .. ok
    + change_pass .. ok

So, are the changes deployed?

  > mysql -u root -D flipr_test --execute "
      DELETE FROM users;
      CALL insert_user('foo', 'secr3t');
      CALL insert_user('bar', 'secr3t');
      SELECT * FROM users;
  "
  +----------+---------------+----------------------------+
  | nickname | password      | timestamp                  |
  +----------+---------------+----------------------------+
  | bar      | 0aasvM1.AzY0Y | 2013-12-31 22:14:45.554942 |
  | foo      | 80v1DpnRrqbwo | 2013-12-31 22:14:45.554457 |
  +----------+---------------+----------------------------+

Awesome, the stored passwords are different now. But can we revert, even though we haven't written any reversion scripts?

  > sqitch revert --to @HEAD^^ -y
  Reverting changes to delete_flip @v1.0.0-dev2 from flipr_test
    - change_pass .. ok
    - insert_user .. ok

Did that work, are the "MD5()" passwords back?

  > mysql -u root -D flipr_test --execute "
      DELETE FROM users;
      CALL insert_user('foo', 'secr3t');
      CALL insert_user('bar', 'secr3t');
      SELECT * FROM users;
  "
  +----------+----------------------------------+----------------------------+
  | nickname | password                         | timestamp                  |
  +----------+----------------------------------+----------------------------+
  | bar      | 9695da4dd567a19f9b92065f240c6725 | 2013-12-31 22:15:29.843140 |
  | foo      | 9695da4dd567a19f9b92065f240c6725 | 2013-12-31 22:15:29.842700 |
  +----------+----------------------------------+----------------------------+

Yes, it works! Sqitch properly finds the original instances of these changes in the new script files that include tags.

But what about the verify script? How can we verify that the functions have been modified to use "ENCRYPT()"? I think the simplest thing to do is to examine the body of the function as returned by "INFORMATION_SCHEMA.ROUTINES" <http://dev.mysql.com/doc/refman/5.6/en/routines-table.html> So the "insert_user" verify script looks like this:

  -- Verify flipr:insert_user on mysql

  BEGIN;

  SELECT sqitch.checkit(COUNT(*), 'Procedure "insert_user" does not exist or is not up-to-date')
    FROM mysql.proc
   WHERE db = database()
     AND specific_name = 'insert_user'
     AND body_utf8 LIKE '%ENCRYPT(md5(password), md5(FLOOR(RAND() * 0xFFFFFFFF))%';

  ROLLBACK;

And the "change_pass" verify script looks like this:

  -- Verify flipr:change_pass on mysql

  BEGIN;

  SELECT sqitch.checkit(COUNT(*), 'Procedure "change_pass" does not exist or is not up-to-date')
    FROM mysql.proc
   WHERE db = database()
     AND specific_name = 'change_pass'
     AND body_utf8 LIKE '%ENCRYPT(md5(oldpass), password)%';

  ROLLBACK;

Make sure these pass by re-deploying:

  > sqitch deploy
  Deploying changes to flipr_test
    + insert_user .. ok
    + change_pass .. ok

Excellent. Let's go ahead and commit these changes:

  > git add .
  > git commit -m 'Use encrypt() to encrypt passwords.'
  [master abcce73] Use encrypt() to encrypt passwords.
   13 files changed, 137 insertions(+), 9 deletions(-)
   create mode 100644 deploy/change_pass@v1.0.0-dev2.sql
   create mode 100644 deploy/insert_user@v1.0.0-dev2.sql
   create mode 100644 revert/change_pass@v1.0.0-dev2.sql
   create mode 100644 revert/insert_user@v1.0.0-dev2.sql
   create mode 100644 verify/change_pass@v1.0.0-dev2.sql
   create mode 100644 verify/insert_user@v1.0.0-dev2.sql

  > sqitch status
  # On database flipr_test
  # Project:  flipr
  # Change:   6f2e1cd4b1c031a66930811328cfcdb0389d8320
  # Name:     change_pass
  # Deployed: 2013-12-31 14:16:45 -0800
  # By:       Marge N. OXVera <marge@example.com>
  # 
  Nothing to deploy (up-to-date)

More to Come

Sqitch is a work in progress. Better integration with version control systems is planned to make managing idempotent reworkings even easier. Stay tuned.

Author

David E. Wheeler <david@justatheory.com>

License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.