The Art of Doctrine Migrations

Nashville symfony Group The Art of Doctrine Migrations Feb 2nd, 2010 Ryan Weaver @weaverryan iostudio.com www.thatsquality.com

Nashville symfony Group Feb 2010 So you've updated your code, now to update your database...  PhpMyAdmin: post-it notes, pizza & beer  SQL deltas:  Pros: familiar syntax, tools available  Cons: not systematic, db-specific, disconnected from ORM  Doctrine Migrations:  Pros: systematic, generate automatically, written in Nashville (probably)  Cons: were a pain in the ass (until now), still a bit quirky

Nashville symfony Group Feb 2010 A PHP file with simple directions on how to update your database Each file is prefixed by a number, which determines its ordering: /lib/migration/doctrine/  1_add_brilliant_idea_table.php  2_add_good_people_table.php  3_add_desc_field_to_idea.php

Nashville symfony Group Feb 2010 Tracking Versions Doctrine keeps track of your db's “version” via migration_version table /lib/migration/doctrine/  1_add_brilliant_idea_table.php version 1  2_add_good_people_table.php version 2  3_add_desc_field_to_idea.php version 3  4_modify_some_column.php version 4  35_alternatively_numbered.php version 5

Nashville symfony Group Feb 2010 Take a deep breath and migrate: ./symfony doctrine:migrate [migration #]

Nashville symfony Group Feb 2010 Writing Migrations Create a blank migration file: doctrine:generate-migration name  Creates a blank file in lib/migration/doctrine (e.g. 1265085881_add_another_table.php)  Use the rich API to make changes www.doctrine-project.org/Doctrine- Cheat-Sheet-1.1.pdf

Nashville symfony Group Feb 2010 Or just generate the migrations automatically...

Nashville symfony Group Feb 2010 Generate Migrations For an existing database & project with no migrations: doctrine:generate-migrations-db • Generates migration classes for everything to date • For example, for a project with 75 tables, this would generate 76 migration classes • (1 per table + 1 giant class for all indexes and foreign keys) This gets you “caught up”, but only works once.

Nashville symfony Group Feb 2010 Migration-diff tool Generates new migration class(es) based on some schema change 1) Make a change to your schema (e.g. add a column) 2) Run the diff tool task: doctrine:generate-migrations-diff 3) Rebuild your model doctrine:build --all This runs a “diff” between your new schema and your old model files. Lame/Warning: If you rebuild your model before running the diff tool, no changes will be recognized

Nashville symfony Group Feb 2010 Filename Conventions Generated migrations take one of these 2 forms: 263866565_migration_name.php 263866565_version15.php We recommend renaming to include the version #: version1_migration_name.php 263866565_version15.php

Nashville symfony Group Feb 2010 Model Name Conventions Generated migrations take one of these 2 forms: class Version15 class MigrationName We recommend naming the class by the version #: class Version 15

Nashville symfony Group Feb 2010 Data Migrations – easy, but... Also can use: - preUp() - preDown() This will break eventually, when you make changes to the BrilliantIdea model (e.g. in 2 months, you remove the name field)

Nashville symfony Group Feb 2010 Doctrine Migration – Ruining your day 1) NEVER mix foreign-key changes with table or column changes Major $this->createTable('brilliant_idea',...) migration $this->createForeignKey('brilliant_idea', …) foul 2) If you care, be careful with your index names Name 'product_slug' becomes 'product_slug_idx'

Nashville symfony Group Feb 2010 Tools – MySQLdiff (http://www.mysqldiff.org/) • Simple: compares two databases and gives you a list of their differences – build-all-reload your main database – Migrate your test database

Nashville symfony Group Feb 2010 Discussion Notes from the Presentation Migration Failures Suppose you're migrating from version 2-10 and migration #5 fails: ● Migrations 6-10 will continue to try to run ● The migration_version table will still be set to 2 after the migration, even though versions 3 & 4 were successful

Nashville symfony Group Feb 2010 Discussion Notes from the Presentation generate-migrations-db ● In theory, this task compares your db to your models and generate migrations based on the difference. ● After weeks of dev, all migrations could be generated at once ● At least 2 bugs exist in this task: ● http://pastebin.com/f7e11c784 ● Models prefixed with a lowercase letter will not work. But, this does not affect most MACs

Nashville symfony Group Feb 2010 Discussion Notes from the Presentation Resetting your migrations ● To battle “broken” migrations that result from data migrations that reference no-longer-used fields, it may be a good idea to adopt a strategy of periodically “resetting” your migrations: ● Delete all migration files ● Run doctrine:generate-migrations-db ● Manually set your migration_version number to the last, newly-generated migration file

Nashville symfony Group Feb 2010 Discussion Notes from the Presentation Autoloading Bugs in generate-migrations-diff ● When using the diff tool, you may get an error such as: “Cannot find class PrfxSomeClass” ● The diff tool generates temporary models and in some cases (specifically doctrine model subclassing) will require the files in the wrong order ● There is a hack (try the autoload.yml hack): ● http://trac.symfony- project.org/ticket/7272#comment:13

Nashville symfony Group Feb 2010 Questions? Idea Bubbles? Ryan Weaver @weaverryan iostudio.com www.thatsquality.com

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The Art of Doctrine Migrations

by Ryan Weaver

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