#100DaysOfWeb in Python Transcripts
Chapter: Days 61-64: Database migrations
Lecture: Concept: Review configuring Alembic
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0:00
Let's review getting started. You can follow along on Mike Bayer's tutorial which you can see the link at the bottom.
0:06
But the short version is we're going to get started by installing Alembic. So here, we're just typing pip install alembic.
0:12
In our example, we actually put it into the setup requirements. That didn't go so well so we put it into our requirements file.
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So, we'd run this, it's going to install Alembic and then we're going to run the init command. Alembic init, and then we give it a folder.
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The convention is also to call the folder it's going to create alembic, does a bunch of stuff. See it creates these alembic folders
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it creates the versions and so on and then finally says, hey you need to edit the alembic.ini before you get going. Alright, we'll come back to that
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but let's first talk about the project structure. So, as we work with it, you'll see it starts to develop a structure that looks like this.
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So we have our alembic folder that's the folder that we specified in the init command and it has versions.
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These are, the change that take our base model our base schema, and then migrate through the various changes over time.
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Each one of these changes, or levels is recorded in the database, as we'll see. So, Alembic can look at your database
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look at the various changes, and it says well I'm starting from here and I want to get to the latest. What path do I have to take?
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What set of changes do I apply to do that? That's what's in these files, and we'll see how to work with them in a minute.
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We have some more setup we can do here. We're going to mess with this env.py in just a second and we also have our alembic.ini.
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That's where we specify the configuration settings. Most importantly, how do we talk to the database? What's the connection string?
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Speaking of which, in that alembic.ini we're going to say sqlalchemy.url is a relative path in this case maybe a server name
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in more production type of cases, over to our database. So we said it's in the bill tracker directory db/buildtracker.sqlite, and of course
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we use the sqlite schema; this is a sqlalchemy connection string not a pure sqlite connection string. So we specify that there so we let Alembic know
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how to connect to our database and of course if you have authentication that has to go here, all that kind of stuff.