Question

I have Rails app, and every once in a while, when I bring new developer onboard they exclaim that they should be able to produce the current DB schema in their dev environment by running the whole history of the migrations. I personally don’t think that migrations is the authoritative source for your schema. Right now what we do is load a production copy of the DB, with the current schema, onto the dev machine. And, from there, the schema can be maintained via incremental migrations.

So my question are:

• What is the authoritative source of your schema on a Rails project?
• What is now considered the best-practice way to maintain your DB schema?

Answer 1

I do not consider migrations to be the authoritative source for your schema. Migrations are extremely powerful but optional. Some developers use alternative workflows especially in environments where DBA’s insist on strong referential integrity and DBMS-enforced constraints. I suggest looking at the official RoR Guide on Migrations for more information. The db/schema.db (or db/{env}_structure.sql) file is the authoritative source for your schema. Many developers will purge old migrations as projects get older so running each migration will not necessarily produce a working database. It also takes a long time to run through a hundreds of migrations. Rails uses schema.db (or the sql dump file) to build the test database and of course when running rake db:setup which is the recommended way of creating a new database for your application.

Bottom like is that rake db:setup should always produce a working database regardless of migrations. Developers can use this to create new environments and Rails uses this to run your tests.

http://guides.rubyonrails.org/migrations.html#schema-dumps-and-source-control