I wanted to create database tables from model definition in loopback4. How to do that using loopback4's Auto update functionality?
You can use the npm run migrate script in the LoopBack4 application. See https://loopback.io/doc/en/lb4/Database-migrations.html for details. Please note that there is an option to drop existing schemas before creating a new one.
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I use flyway for DB schema migrations.
But now I also want to make it possible to dynamically create a new database (for testing), update it to the latest schema, and fill it with test data.
Is it possible to have flyway baseline a new DB and apply ALL schema version scripts sequentially so the DB is updated to the latest state?
I could not find any examples of this. I don't want to have a separate process or scripts for creating a new DB with the right schema.
I am using Google Cloud Datastore(not NDB) for my project.
python2.7 and Django.
I want to create a new model, lets say Tag model.
class Tag(db.Model):
name = ndb.StringProperty()
feature = ndb.StringProperty(default='')
I have added property to a model many times, but not yet created new model.
My question is when I have changed model schema in Django for my another project using mySQL, I always executed manage.py migrate.
Do I have to execute the migration command for Datastore as well?
Or just defining the model is all I have to do?
Thanks in advance!
Unlike SQL databases like MySQL, Cloud Datastore doesn't require you to create kinds (similar to tables) in advance. Other than defining it in your code, no admin steps are required to create the kind.
When you write the first entity of that kind, it's created implicitly for you.
You can even query for kinds that don't exist yet without an error, you'll just get no entities back:
Of course you have to migrate, except if you are using the same database from the another project. Anyway if you type migrate it will create the tables from your models but if you are working with a existing database nothing is going to happen
I'm pretty new to Django and it's deployment on Heroku.
I've got a Postgres database up and running on the app server. My app requirements need me to add a new column to my existing database which has a sizable amount of data in it, which I can't lose.
Looking around, I found a solution described by Mike Ball here.
I have the following queries though:
What exactly is South? (I read the docs but didn't get a clear idea)
Will it help me save and move my existing data from my current database?
As a complete newbie, is the above link an easy way to move the data?
Also, in general, if you could hook me up with a good guide for general DBMS concepts, I'd be very grateful.
Thanks!
What exactly is South? (I read the docs but didn't get a clear idea)
south migrates your database schema as it changes in time. the schema has to start with a django models.py file. If you use 'manage.py syncdb ...' to create your database then you can probably use south.
Will it help me save and move my existing data from my current database?
As long as you used syncdb to create your database using a models.py file in django, then south can change that database and add the new column. basically, south records the changes you make to the models.py file in migration files, then you can apply those migration files to your database which update it non-destructively.
As a complete newbie, is the above link an easy way to move the data?
south doesn't move your data. it allows you to add the new columns to your existing database without destroying the database. to move your data you will need to backup the data to a file, then copy the file to another machine, then restore the backup. That's not what south does.
When my Django project is installed, the db is created and my fixtures are used to populate the db, this normal work flow works great. However at a specific time (after the db and its content are created) I want to alter an existing record in the db.
Is there a way to programmatically alter a record in an existing database table? Perhaps using python manage.py sqlall? If possible I want to avoid a 'hackish' solution like writing a little script that will run a sql alter command.
You could create a python script, import your Django models and do the changes just like within a Django application. Then execute that script on the given time.
I just tested it myself. I had Django models, and there have already been instances of the models in the database.
Then I added a dummy integer field to a model and ran manage.py syncdb. Checked the database, and nothing happened to the table. I don't see the extra field added in.
Is this the expected behavior? What's the proper way of modifying the model, and how will that alter the data that's already in the database?
Django will not alter already existing tables, they even say so in the documentation. The reason for this is that django can not guarantee that there will be no information lost.
You have two options if you want to change existing tables. Either drop them and run syncdb again, but you will need to store your data somehow if you want to keep it. The other options is to use a migrations tool to do this for you. Django can show you the SQL for the new database schema and you can diff that to the current version of the database to create the update script.
You could even update your database mannually if it is a small change and you don't want to bother with migrations tools, though I would recommend to use one.
Please use south for any kind of changes to get reflected to your database tables,
here goes the link for using south
Link for South documentation