Building data-driven web apps with Flask and SQLAlchemy Transcripts
Chapter: Database migrations with Alembic
Lecture: Concept: Getting started
0:00 Let's take a moment and review
0:01 the core concepts of using Alembic.
0:03 And I think the place to get started is getting started.
0:06 The way we're going to get started is
0:07 we have to make sure we have Alembic.
0:09 We simply get that by pip installing Alembic.
0:12 Make sure this is the virtual environment
0:14 that you want it to be in, okay?
0:16 So that works great, let's go into install.
0:18 Then we need to initialize the project structure just once.
0:21 So we say alembic init alembic.
0:24 First one is the command, last one is the folder.
0:26 And then it's going to go through and create all the structure.
0:28 And says, don't forget
0:30 you have to set your connection string
0:31 in alembic.ini or this isn't going to work.
0:34 Afterwards, you have a project
0:36 that looks a little bit different.
0:38 You've got an alembic folder, and here we have versions.
0:42 It's going to be initially empty but as you apply
0:44 as you create revisions
0:46 they're going to be stored in here
0:47 and chained together as we saw.
0:49 Some scripts that are used to
0:52 generate the SQL and run Alembic.
0:55 So environment does things like
0:57 tells Alembic what your SQLalchemy models are
1:00 the scripts stop.py and .mako is actually
1:03 going to generate the SQL structure
1:06 that's going to be sent to the database.
1:08 Things like that.
1:09 Then finally we have our alembic.ini
1:11 that configures how Alembic runs.
1:14 In order to use Alembic you have to configure it.
1:17 So there's a whole bunch of settings
1:19 in Alembic.ini but the one that you
1:20 probably care about first is sqlalchemy.url
1:23 and then you just set it to whatever
1:25 your connection string is.
1:27 We're using SQLite so it's sqlite/// the name of the file
1:31 and were able to use a relative path.
1:33 I think this may only work if you run
1:35 Alembic from the right location, so do that.
1:39 Turns out that's pretty easy from PyCharm
1:41 cause the terminal always opens in the right place.