I'm working on blacklisting these for the data analysis tool Metabase.
I can't find any lists anywhere that specify which tables the framework creates, but I want to make sure I get db migration / ActiveRecord ones and other internal ones created by the framework that a user likely wouldn't be interested in looking at.
The only table that Rails (or rather ActiveRecord) creates regardless of application models is schema_migrations.
By default rails does not create any table when you create a new app.
But when you add a migration for create table that time rails create a table schema_migrations and that is used to save version of the migrations.
This table will create with first table when run rake db:migrate
Related
I am new to Ruby on Rails, so I have some confusion about rails migration.
I want to add a field on my user table, according to rails documentation is only possible by using
rails generate migration add_field_name_to_table_name field_name: type
Question
Is it possible to add fields to the existing database table without rails g migration in rails? Thanks...
The bigger question is why you need to do that. I mean to imply that whatever makes you think that you need to do this is wrong (I am pretty confident about it, assuming you are a new rails user). It is like you would leave your plane without a reason for a long-distance flight to travel by foot.
Answer:
You can do that by:
logging in to Postgres manually like rails db
then creating table manually the SQL way
then adding the table manually with correct columns in your schema.rb file
then creating a model manually
You still will have to repeat this every time this project is cloned anywhere else with no window for mistake. With migration, on the other hand, you will just need to do rails db:migrate
Happy Coding.
I am trying to build a read-only Rails API that uses another Rails application's DB as its database.
So far I configured the read-only API's database.yml to point to the existing databases, generated models via rails g model but did not run the migration since I already have the corresponding tables in the existing databases.
I wanted to follow TDD approach and started to write tests but my problem is I cannot create instances of models since I did not create the table for that model.
Example Case
I generated a model named project which exists as a table in the existing DB that I am going to use to read data, but since I did not run the migration for that model it does not exist in the current API's DB.
So, I just dumped the schema.rb from the existing DB, copied it as my read-only API's db/schema.rb and run rake db:schema:load when RAILS_ENV=test.
I wonder if there's a better way to do this? Is my way of writing a read-only API like this is correct? I am open to any suggestions for this topic.
Cheers.
The question pretty much says it all.
I'm new to Ruby and Rails and I'm trying to figure out active record. According to a few pieces that I've read, Rails will interrogate the database (in my case PostgreSQL 9.6) and pick up the columns from that. The way I read this, does that mean I can create the database in PostgreSQL, create ORM classes and define the relationships in the ORM classes?
My background is in databases and it's been a while since I've done any web development and prior to 1/8/2018 I had never even touched Ruby let alone Rails. So, the ultimate question is: Can I create the database in PostgreSQL without Rails migrations and then create the ORM classes with the relationships between the classes (tables) defined in them?
Yes, absolutely! You'd just need to connect to the existing db in config/database.yml and generate a schema file by running rake db:schema:dump. Remember to go by Rails naming conventions for ORM Classes (called Models in RoR). You can also explicitly set table names for every model by adding self.table_name = "posts" (see this answer)
I have connected my app to a MS SQL database, but I wanted to know how I can start referencing the data that was already in the database (but in another table). Do I have to generate anything in my app / resources etc.?
As Dharam said, you need to genereate Active Record model. Rails using MVC architecture, if you need to learn first about MVC, go to Rails getting started.
If you already have table, with data and structure, you don't need to generate it, you can generate ActiveRecord model without migration with this command.
rails g model ModelName --migration=false
So what's the best way to create new tables in a Sqlite database in Rails 2. I have created the database using rake db:migrate command. So should I write individual sql scripts to create a database or use rake somehow. I don't need scaffolding.
Basically use migrations.
Some useful help on how to use migrations is available at http://wiki.rubyonrails.org/rails/pages/understandingmigrations and http://wiki.rubyonrails.org/rails/pages/UsingMigrations. A good cheatsheet that I use is also available at http://dizzy.co.uk/ruby_on_rails/cheatsheets/rails-migrations.
Basically migrations use ruby code to create your database tables for you. It is far easier (in my opinion at least) to use nice ruby code to do this rather than SQL DDL - it also does various things automatically for you (like adding id fields to all your tables as rails requires). You can then use rake tasks to actually apply the migrations to your database. The other major advantage that migrations give you is that they are reverseable - so your database is versioned and you can easily jump from one version to another.
Try to avoid writing CREATE/ALTER table scripts and use ActiveRecord migrations instead. A few reasons spring to mind:
Portability: it's much easier to let
AR deal with cross-platform flavour
differences
Change control: your
migrations can manage changes in
both directions with the VERSION=
option, something that's not easy to
do with SQL
It's the Rails way:
follow the Rails conventions unless
you have a compelling reason not to
do so
Simplicity: you don't have to worry about id and timestamp columns when you use migrations, which saves you having to remember them if you work in SQL
If you are not using scaffolding then you should use script/generate migration to create a migration file for each table. There is no need to use sql scripts. After creating some migrations you can apply them to your database using rake db:migrate.