Building Data-Driven Web Apps with Pyramid and SQLAlchemy Transcripts
Chapter: Database migrations with Alembic
Lecture: Concept: Getting started
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Let's take a moment and review
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the core concepts of using Alembic
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and I think the place to get started is getting started.
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The way we're going to get started is we have to make sure
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we have Alembic. We simply get that by pip install alembic
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make sure this is the virtual environment
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that you want it to be in, okay?
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So that works great; let's go install
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then we need to initialize the project structure
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just once, so we say, alembic init alembic
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first one is a command, last one is the folder
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and then it's going to go through and create all the structure
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and says don't forget you have to set your connection string
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in Alembic.ini or this isn't going to work.
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Afterwards, you have a project that looks a little bit different;
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you've got an Alembic folder and here we have versions.
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They're going to be initially empty but as you apply
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as you create revisions they're going to be stored in here
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and chained together as we saw.
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Some scripts that are used to generate the SQL
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and run Alembic so environment does things like tells Alembic
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what your sqlalchemy models are
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the script.py.mako is actually going to generate
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the SQL structure that's going to be sent to the database
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things like that. And finally, we have our Alembic.ini
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that configures how Alembic runs.
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In order to use Alembic, you have to configure it
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so there's a whole bunch of settings in Alembic.ini
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but the one that you probably care about first
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is sqlalchemy.url and then you just set it
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to whatever your connection string is.
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We're using SQLite so it's sqlite:/// the name of the file
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and we're able to use a relative path
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I think this may only work
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if you run Alembic from the right location
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so do that. Turns out that's pretty easy from PyCharm
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cuz the terminal always opens in the right place.
