You can run, for example, git checkout -ours when merging or git checkout -theirs when rebasing, followed by mix ecto.migrate, and that’s it, you did it. Second, you’ll have to depend on two commands now rather than one – for new systems mix ecto.load, for old systems mix ecto.migrate, these two options can make it a bit harder to integrate into some DevOps release strategies.Īs for the first problem, if you’re using git, you can use its power instead of touching your structure.sql. First, it’s a huge file, and any branching conflicts that happen in it can be painful to solve. There are two downsides to having a structure.sql file. Something is rotten in the state of Denmark For existing setups, you can keep running mix ecto.migrate as usual. For brand new setups, you can run mix ecto.load and it will skip all the migrations and load up the structure.sql file. If the code above, every time you run mix ecto.migrate or mix ecto.rollback it updates your structure.sql file by dumping your database structure. For example, in your mix.exs file: defp aliases do You can keep the structure.sql file updated by hooking the ecto.migration and ecto.rollback commands to dump the structure of the database. If you then try to ecto.migrate after loading the structure, nothing happens, because everything is already there. By using running mix ecto.load, Ecto uses the structure.sql file to load the database structure, skipping running all of the migrations and, in the same operation, you can still have all migrations tracked in the schema_migrations table just as before. You have to keep that file in your source code, and that contains the most recent structure of your application database. ecto.load and ecto.dump for the rescue!Įcto SQL gives you the option to keep a structure.sql by running the mix ecto.dump command. No code runs faster and is easier to maintain than any code. I don’t know about you, but for me, that sounds like a waste of time. That would mean maintaining files that were run only once in production they don’t even need to run there anymore. If you removed the old modules, you’d have to remove those references from your migrations as well. The problem can be even worse if your old migration files are referencing old module functions for some reason. The last two files negate the effects of the previous ones it means we have four unnecessary files in our migrations folder that could be either skipped or deleted. After a while, we deleted the flags table and the age column from users. In this example, without looking at the contents of each file, we can see that we created a flags table and we added an age column to the users table. However, if your software is a constant change, after a while, these migrations may stop making sense altogether. That’s a very efficient way to organize and keep track of your database changes. You can also check the migration status by doing mix ecto.migrations. These filenames begin with a timestamp, and Ecto uses that information to keep track of which migrations have or have not been run, and it does so in a table called schema_migrations. The migration files usually live on priv/repo/migrations of your application folder. Someone in your team had to write a migration file. If you’re using Ecto SQL, you also have to run mix ecto.migrate – then voilà, your database is now in the most recent version. When you run git pull in your terminal to get code updates, it doesn’t automatically update your database changes. Your application’s source code and your database live in different universes. Migrations: a love and hate relationshipīefore we move on, let’s go through a little more context so we can be on the same page. Ecto SQL 3.1.2 added a -skip-if-loaded option that skips the database structure load step when it has already been loaded, allowing you to create a robust pipeline. However, that command is not easy to fit in all workflows. That’s why the library provides the ecto.load mix task, which allows you to get rid of an ever-increasing amount of files. These files, after a long time, can be painful to maintain. If you’re building or maintaining an application that has a SQL database, you need a way to keep track of structural changes. There is a well-known truth about software development: if your software is useful, it will change.
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