I have few questions about this plugin.
1- what does it do?
Is it for exchanging databases between teams or changing their schema or creating tables based on models or something else?
2- if it is not meant to create tables based on models where can I find a script that does this?
3-can it work under windows?
thanks
The Migrations plugin allows versioning of your db changes. Much like is available in other PHP frameworks and Rails.
You essentially start with your original schema and create the initial migration. Each time you make a change you generate a 'diff' that gets stored in the filesystem.
When you run a migration, the database is updated with the changes you made. Think deployment to a staging or production server where you want the structure to be the same as your code is moved from environment to environment.
We are starting to look at this plugin so we can automate our deployments, as the DB changes are done manually right now.
Related
I am facing a challenge here. So I inhertied the models from previous developers and the tables were not properly built. I added some constraints and new tables in order to normalize those tables. Before pushing the application to the heroku I tested it on my local machine and it actually broke my database.
Now the heroku website is already in production, so there are user information. How should i approach this, do I need to destroy the existing database and create a new one and run the migrations
Be very, very careful. Applying migrations on production servers can cause irreversible damage if you are not careful, and so you should be prepared for every possible situation.
My best recommendation would be to create an entire duplicate copy of your live DB (using Heroku this is as simple as a PG dump/backup). You can then create a new staging site using the same code, upload the backup into a new Database instance, and then test against that. Live environments are not always the same as local ones. You can then run your migrations on the staging site, and see if there are any unexpected effects (the best way to do this would be by utilizing django test cases). If there are any issues, be sure to understand how the rollback process works with django migrations.
A good tutorial that is fairly recent can be found here: https://realpython.com/django-migrations-a-primer/
I'm using Django and Postgresql to develop a web service.
Suppose we've 3~4 branch which for the different features or old-version bugfix purpose.
Then, I met a problem, when I was in branch A and change django model, and run migrate to change database in my local test desktop.
When I switch to another branch which has no migration file, database will inconsistent and cannot work when I try to run django, I've to delete the database and recreate it.
In general, what's the best/common way to deal with this kind demands for developer environment?
I understand your situation well and have been in same shoe several times.
Here is what I prefer(/do):
I am in branch bug-fix/surname_degrade
I changed the user data model [which generated user_migration_005] and then migrated the DB.
Then my boss came and pointed out that the user is not able to login due to login degrade.
So I have to switch branch and fix that first.
I can rollback the migration[user_migration_005] which I have done few moments back. With something like this python manage.py migrate user_migration_004
Switched branch and started working on hot-fix/login_degrade
When I switch back to my previous task , I can just do migration and proceed.
With this procedure I don't need to delete my all tables or restore old database or anything like that.
I am a newbie, will be extremely happy to hear your thoughts.
The major issue here is that, you database will change everytime You migrate,so either you mantain you database consistency among different branches, or You can do One thing, while using/testing (after declaring all the models)
1) Delete all database tables ( If you have a backup or dummy data )
2) Delete all existing migration files in you branch
3) Create new migrations
4) Migrate to new migrations
The above steps can also be done if the models are re modified, after modification just repeat the steps.
Run a different test database in each branch.
When you fork the design, fork the database
Make a clone of the database and migrate that.
Make sure when you push to git, you include your migrations, that wait when someone else pulls the branch and does a migrate django knows what changes were made to the database.
I have setup a git repository and cloned open source code which I am planning on modifying from github to start development. I committed the codebase in our repository.
I now have added few users and posts and other "stuff" into database.
I want to commit this change as well so that my teammate can check out and we have same settings and database throughout.
Is this possible by using south migrations? i.e will database bot contents and schema be in sync as well?
I have the project where I am writing the code as well the actual app. Should I commit both of them.
What should the github repository look like after doing the "right" thing
Data and database structure
This is possible using south migrations, data migrations and fixtures.
The easiest way for development is to just use a SQLite database, which is a binary file that you can commit. The test_project of django-autocomplete-light demonstrates such a possibility: http://django-autocomplete-light.readthedocs.org/en/latest/demo.html
you must use south anyway !
Apps in the project repo
I think you should keep apps as small and loosely coupled as possible.
If sound, make another repository and python package for the app:
In some cases it makes sense at the beginning, ie. a "blog" app that you know you will reuse,
In some cases it makes sense later, ie. you tought your app was really project specific but then you want to reuse it in another project,
In some cases it never makes sense (ie. the app is only useful to that particular project).
Best practice
As for best practices, there is http://12factor.net, http://lincolnloop.com/django-best-practices/ and pinax projects which are really interresting.
If you're going to reuse and extend external apps, then maybe this article on best practice reusing apps can help.
If there is data that every developer needs, these can be provided by initial_fixtures. I have just begun to use south, but I think it is mainly for migrations, (changing your models, without having to delete your data, and resync) not for sharing data. Schema should always be in sync using south, because a developer can pull the south migration, and apply it.
During development, I like the idea of frameworks like Entity Framework 4.3 Migrations (although I need it to work with sql scripts instead of Migration classes) keeping all developer databases up-to-date. Someone does an update to get the latest source, they try to run the application and get an error that they need to update their database to the latest migration (or have the migration happen automatically). Migration files are timestamped so devs don't have to worry about naming two files the same or the sequence the files need to be executed in.
When I get ready to build a WebDeploy deployment package, I want the package to contain the scripts required to move the production database to the latest db version. So somehow, MSBuild or WebDeploy need to make a decision about which scripts must be packaged. For deployment I don't want the application to try to update itself like what EF offers. I want to either hand the package to the IT department or do an auto-deploy through a deployment server.
Some of my questions are:
Can EF 4.3 work with sql scripts instead of DBMigration classes for my development needs (I'm already using it for my ORM so it would be nice if it could)?
Does MSBuild or WebDeploy understand the concept of database migrations (e.g. does it recognize the EF. 4.3 migrationHistory table) or do I have to make sure to give it just the scripts it needs to run that will bring my prod db to the latest migration? Manually deciding which scripts should be pakaged is not something I want to do so is there a MS WebDeploy extension that understands migrations?
Are my concerns and ideas valid? I'm just researching this stuff so I don't really know.
I think that your concerns are valid. During development anything that keeps the developer machines in sync will do. When deploying, more control is needed.
In my project we've decided to only use code-based migrations, to ensure that all databases are migrated in the same order with the same steps. Automatic migration and db creation is disabled by a custom initialization strategy that only checks that the db exists and is valid.
I've written more about the details in Prevent EF Migrations from Creating or Changing the Database. I've also looked a bit into merge conflicts which will eventually happen with multiple developers.
You can run SQL in the classes by calling the Sql method, or generate SQL from a migration by using the -script parameter with the update-database command.
No. They were looking at adding support for webdeploy but apparently decided against it before rtm. They did however release a command line app (and powershell script obviously) which you could call from either.
What I do in my projects is create an startup module in my applications and run any migrations that haven't been deployed automatically - Triggering EF migration at application startup by code. It's not perfect, developers have to run the app after getting latest before changing the db, but it works for both get latest and deployment.
Overview
I'm building a website in django. I need to allow people to begin to add flatpages, and set some settings in the admin. These changes should be definitive, since that information comes from the client. However, I'm also developing the backend, and as such will am creating and migrating tables. I push these changes to the hub.
Tools
django
git
south
postgres
Problem
How can I ensure that I get the database changes from the online site down to me on my lappy, and also how can I push my database changes up to the live site, so that we have a minimum of co-ordination needed? I am familiar with git hooks, so that option is in play.
Addendum:
I guess I know which tables can be modified via the admin. There should not be much overlap really. As I consider further, the danger really is me pushing data that would overwrite something they have done.
Thanks.
For getting your schema changes up to the server, just use South carefully. If you modify any table they might have data in, make sure you write both a schema migration and as necessary a data migration to preserve the sense of their data.
For getting their updated data back down to you (which doesn't seem critical, but might be nice to work with up-to-date test data as you're developing), I generally just use Django fixtures and the dumpdata and loaddata commands. It's easy enough to dump a fixture and commit it to your repo, then a loaddata on your end.
You could try using git hooks to automate some of this, but if you want automation I do recommend trying something like Fabric instead. Much of this stuff doesn't need to be run every single time you push/pull (in particular, I usually wouldn't want to dump a new data fixture that frequently).
You should probably take a look at South:
http://south.aeracode.org/
It seems to me that you could probably create a git hook that triggers off South if you are doing some sort of continuous integration system.
Otherwise, every time you do a push you will have to manually execute the migration steps yourself. Don't forget to put up the "site is under maintenance" message. ;)
I recommend that you use mk-table-sync to pull changes from live server to your laptop.
mk-table-sync takes a lot of parameters so you can automate this process by using fabric. You would basically create a fabric function that executes mk-table-sync on each tablet that you want to pull from the server.
This means that you can not make dabatase changes yourself, because they will be overwritten by the pull.
The only changes that you would be making to the live database are using South. You would push the code to the server and then run migrate to update the database schema.