I have tables and it's schema. I neither have the database nor Sqlalchemy models. How do I generate alembic first version script with this information?
P.S. I could create a database with existing schema if that could be of help to get the alembic scripts.
you can use sqlcodegen to generate the sqlalchemy models, then create an empty database and use these models to create the initial alembic script.
Related
I am new to Python ORM world.
I wanted to generate model (code) from the existing database in Alembic or SQLAlchemy.
I could find any docs about that. Just simply having already created database, I would like Alembic to generate me classes for that database for each table.
Is there any way to achieve this?
Alembic is used for migration. You can read more about it here Alembic Project Description
SQLAlchemy is an ORM that translates Python classes to tables on relational databases not vice versa.
This online tool create-class-from-database-table may help you to get classes from database tables
I'm relatively new to neo4j and want to integrate an existing database in django for python with neomodel (django-neomodel).
Can the corresponding node models be derived from the existing neo4j database? Like inspectdb for relational databases in django..
If not, I'm able to write the models myself. Do I need to execute the neomodel_install_labels command afterwards? Because the labels are already there..
Thank you!
Max
I am developing a Flask app that queries on an existing Postgres DB. This DB had been created with Django models. Do i need to reverse engineer so my models would be compatible with SQLAlchemy or will that already be. Is raw queries the way to go? I don't want to create new DBs just query and update some values in the existing ones, that had been created in Postgres using my django models.
Go check out sqlalchemy's AMAZING automap feature: http://docs.sqlalchemy.org/en/latest/orm/extensions/automap.html
Used it once in my personal project for similar purpose, it works great.
Let's say I have the following table showing how the columns would be declared for a MySQL table: (I can't think of a very realistic example, so here's something that's so silly. This table is created with the help of Excel)
I want to create a model in Django that is compatible with the MySQL table I'll have with the columns declared this way. However, from looking at the Django documentation, I can't find any model field types that in SQL are the same format as those in the picture except for the primary key field.
I did see before that by default, Django handles a database that uses the SQLite Engine, but I want to see if it's possible to handle a database of MySQL tables.
Is there a way to create Django model field types, like MEDIUMINT, TINYTEXT, and SMALLINT, (in MySQL) that are compatible with tables created through MySQL? It's simply a way for me to use the tables that I created myself, not the tables that Django generates automatically once all the models are defined.
In Django you normally create the models and let the framework generate the tables for you. If you have a legacy database you can use python manage.py inspectdb to generate the models from the database (see the documentation). But if it isn't a legacy database and you've created it just now, you are fighting against the framework and making your life more complicated.
I have a Flask project with MySQL database and uses SQLAlchemy as ORM and Flask-Migrate*for migrations.
I wrote my models and when I run the migrations, migration file is empty because existing tables are out of Flask-Migrate's control so I actually have to delete those tables to let migration tool to detect and create them again. But the problem is that I do not want to delete and create my tables.
So is there a way that I can sync my model with my existing table ?
EDIT :
I just found out that in env.py file, it's possible to specify tables that exists
and it will not create those tables :
metadata.reflect(engine, only=["table1", "table2"])
Thanks for the answer.
Automatic migrations are by definition generated as a delta between your models and your database. If you already have a database that was created before you started using Flask-Migrate/Alembic then you can begin tracking migrations from that point on.
If you want to generate an initial migration that takes you to your current version the easiest way is to delete all the tables, as you suggested. To avoid losing your data I can suggest two ideas:
backup your database before deleting your tables, then restore after the migration was generated.
temporarily point your application at an empty database (a different one). Once the migration is generated point it back to your database.
I hope this helps.