![]() ![]() > return Mapper(class_, local_table, *args, **params) > File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/_init_.py", line 1129, in mapper When I run 'alembic revision -autogenerate' to create migration script, and got below error: > You can see that Test2 is a table without a primary key. > fid = Column(Integer, ForeignKey(' test1.id')) > id = Column(Integer, primary_key = True) > I have 2 simple tables defined as below: On Dec 1, 2012, at 11:49 AM, junepeach wrote: Non-primary key is not good design, but acceptable in mysql, sqlite, postgresql. So I wonder how to create a migration script for a table without primary key. : Mapper Mapper|Test2|test2 could not assemble any primary key columns for mapped table 'test2' Return Mapper(class_, local_table, *args, **params)įile "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/mapper.py", line 203, in _init_įile "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/mapper.py", line 767, in _configure_pks When I run 'alembic revision -autogenerate' to create migration script, and got below error:įile "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/_init_.py", line 1129, in mapper You can see that Test2 is a table without a primary key. The code has been saved as migrate_example.py file.Fid = Column(Integer, ForeignKey(' test1.id')) Note:- Calling n() prepares your Manager instance to receive input from the command line. Name = db.Column(db.String, unique=True, nullable=False)Įmail = db.Column(db.String, unique=True, nullable=False)Ĭid = db.Column(db.Integer, primary_key=True)Ĭname = db.Column(db.String, unique=True, nullable=False)Ĭlocation = db.Column(db.String, unique=False, nullable=False) Id = db.Column(db.Integer, primary_key=True) Migrate=Migrate(app,db) #Initializing migrate. String, unique = False, nullable = False ) if _name_ = "_main_":įrom flask_migrate import Migrate, MigrateCommandĪpp.config = "sqlite:///data.db" String, unique = True, nullable = False )Ĭlocation = db. Integer, primary_key = True )Ĭname = db. String, unique = True, nullable = False ) class Company (db. String, unique = True, nullable = False ) email = db. add_command ( 'db' ,MigrateCommand ) class Employee (db. Migrate =Migrate (app ,db ) #Initializing migrate. SQLAlchemy is the Python SQL toolkit and Object Relational Mapper that gives application developers the full power and flexibility of SQL.įrom flask_migrate import Migrate, MigrateCommandĪpp. To be explicit, the use of the Flask-Migrate module is intended for Flask applications that are using SQLAlchemy.Īlembic is a lightweight database migration tool for usage with the SQLAlchemy Database Toolkit for Python. What is Flask-Migrate?įlask-Migrate is a wrapper around Alembic, which handles SQLAlchemy database migrations for Flask applications. A schema migration is performed on a database whenever it is necessary to update or revert that database’s schema to some newer or older version. What is Database Schema migration?ĭatabase schema migration refers to the managing of incremental, reversible changes and version control to the relational database schema. ![]() This is when the database migration comes in handy, as it keeps a track of database schema changes for you, and one can easily traverse back to an older or newer version of the database. This post helps you to quickly setup and get started with Database schema Migration using Flask-Migrate.įor example if you already had created a database that contains some tables and now if you add a new column to one of the table and then if you want to revert it to the previous state, it’s difficult to do so. ![]()
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