使用 sqlalchemy 引擎通过代码手动运行 alembic 操作

Question

I invested some time to understand Alemic, how I could run migrations manually without any setup. Due to some reasons we need that, we need to be able to execute operations manually without init, ini files or execution context.

Answer 1

Here is my result:

import sqlalchemy

from alembic.migration import MigrationContext
from alembic.operations import Operations


# Connection
connection_string = 'postgres://xx:@localhost/xxdb'
engine = sqlalchemy.create_engine(connection_string.replace('postgres://', 'postgresql://'))

# Create migration context
mc = MigrationContext.configure(engine.connect())

# Creation operations object
ops = Operations(mc)


# Add column
try:
    ops.add_column('record', sqlalchemy.Column('new_column', sqlalchemy.String))
except Exception as ex:
    print(ex)

# Create table
try:
    ops.create_table('new_table', [
        sqlalchemy.Column('id', sqlalchemy.Integer, primary_key=True),
        sqlalchemy.Column('name', sqlalchemy.String)
    ])
except Exception as ex:
    print(ex)

It lets you run any alembic operation without needing all the stuff around. I just wanted to share that, since it's really hard to get complete examples about it online.