Timestampable & Failed Migrations

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Ok team: I've got one more mission for us: to add createdAt and updatedAt fields to our Question entity and make sure that these are automatically set whenever we create or update that entity. This functionality is called timestampable, and Doctrine Extensions totally has a feature for it.

Activating Timestampable

Start by activating it in the config file: stof_doctrine_extensions.yaml. Add timestampable: true.

Back at the browser, click into the Doctrine Extensions docs and find the Timestampable page. Scroll down to the example... Ah, this works a lot like Sluggable: add createdAt and updatedAt fields, then put an annotation above each to tell the library to set them automatically.

The TimestampableEntity Trait

Easy! But oh, this library makes it even easier! It has a trait that holds the fields and annotations! Check it out: at the top of Question, add use TimestampableEntity.

That's it. Hold command or control and click to open that trait. How beautiful is this? It holds the two properties with the ORM annotations and the Timestampable annotations. It even has getter and setter methods. It's everything we need.

But since this does mean that we just added two new fields to our entity, we need a migration! At your terminal run:

symfony console make:migration

Then go check it out to make sure it doesn't contain any surprises. Yup! It looks good: it adds the two columns.

Back at the terminal, run it with:

symfony console doctrine:migrations:migrate

And... yikes!

Invalid datetime format 0000 for column created_at at row one.

When Migrations Fail

The problem is that our database already has rows in the question table! And so, when we add a new datetime field that does not allow null, MySQL... kinda freaks out! How can we fix this?

There are two options depending on your situation. First, if you have not deployed your app to production yet, then you can reset your local database and start over. Why? Because when you eventually deploy, you will not have any questions in the database yet and so you will not have this error when the migration runs. I'll show you the commands to drop a database in a minute.

But if you have already deployed to production and your production database does have questions in it, then when you deploy, this will be a problem. To fix it, we need to be smart.

Let's see... what we need to do is first create the columns but make them optional in the database. Then, with a second query, we can set the created_at and updated_at of all the existing records to right now. And finally, once that's done, we can execute another alter table query to make the two columns required. That will make this migration safe.

Modifying a Migration

Ok! Let's get to work. Usually we don't need to modify a migration by hand, but this is one rare case when we do. Start by changing both columns to DEFAULT NULL.

Next call $this->addSql() with:

UPDATE question SET created_at = NOW(), updated_at = NOW()

Let's start here: we'll worry about making the columns required in another migration.

The big question now is... should we just run our migrations again? Not so fast. That might be safe - and would in this case - but you need to be careful. If a migration has multiple SQL statements and it fails, it's possible that part of the migration was executed successfully and part was not. This can leave us in a, sort of, invalid migration state.

symfony console doctrine:migrations:list

It would look like a migration was not executed, when in fact, maybe half of it actually was! Oh, and by the way, if you use something like PostgreSQL, which supports transactional DDL statements, then this is not a problem. In that case, if any part of the migration fails, all the changes are rolled back.

Safely Re-Testing the Migration

Anyways, let's play it extra safe by resetting our database back to its original state and then testing the new migration. Start by dropping the database completely by running:

symfony console doctrine:database:drop --force

Then doctrine:database:create to re-create it:

symfony console doctrine:database:create

Next, I'll temporarily comment out the new trait in Question. That will allow us to reload the fixtures using the old database structure - the one before the migration. I also need to do a little hack and take the .php off of the new migration file so that Doctrine won't see it. I'm doing this so that I can easily run all the migrations except for this one.

Let's do it:

symfony console doctrine:migrations:migrate

Excellent: we're back to the database structure before the new columns. Now load some data:

symfony console doctrine:fixtures:load

Beautiful. Back in our editor, undo those changes: put the .php back on the end of the migration filename. And, in Question, re-add the TimestampableEntity trait.

Now we can properly test the new version of the migration. Do it with:

symfony console doctrine:migrations:migrate

And this time... yes! It works perfectly. We can even run:

symfony console doctrine:query:sql 'SELECT * FROM question'

to see those beautiful new created_at and updated_at columns.

Making the Columns Required

The final thing we need to do is create another migration to make the two columns required in the database. And... we can just make Doctrine do this for us:

symfony console make:migration

Go check out the new file. Doctrine: you smartie! Doctrine noticed that the columns were not required in the database and generated the ALTER TABLE statement needed to fix that.

Run the migrations one last time:

symfony console doctrine:migrations:migrate

And... got it! These are two perfectly safe migrations.

Okay, friends, we did it!. We just unlocked huge potential in our app thanks to Doctrine. We know how to create entities, update entities, generate migrations, persist data, create dummy fixtures and more! The only big thing that we have not talked about yet is doctrine relations. That's an important enough topic that we'll save it for the next tutorial.

Until then start building and, if you have questions, thoughts, or want to show us what you're building - whether that's a Symfony app or an extravagant Lego creation, we're here for you down in the comments.

Alright friends, seeya next time.

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