Rails command see all active tables full#
Rails command see all active tables download#

A full stack web developer is familiar with each 'layer' of the software technologies involved in a web application, including data modeling and database technologies, the web server environment and middleware components, network protocols, the user interface and basic visual design and user interaction concepts. This course will give you the basic background, terminology and fundamental concepts that you need to understand in order to build modern full stack web applications. If you want more details on the way our customers use Forest Admin, don't hesitate to contact us.This is the first course in a Coursera Specialization track involving Web Application Architectures.If you want to build your Rails Admin Panel with Forest Admin: visit our website.

Rails command see all active tables download#

Download the ' Rails migrations cheatsheet ' (PDF, Free, no-email requested).

A migration allowing for model evolutions (if this hstore disappears a year from now and a newcomer needs to migrate their DB to the latest), and for data population at the same time (for instance if you are renaming an hstore or some of its attributes) will require 3 successive migration files, where hstore declarations should happen inside the migration files. In general, making hstore migrations fully reversible is not obvious.

When Rails tries to run the migration, the model is called, and this line throws an error, as this same DB column we’re trying to create is supposed to be already available for use by the hstore but does not exist yet.Ī quick fix is to remove the hstore declaration in the model and to migrate, then re-add it. What is happening is that the line declaring the hstore is still present in our model at this point. Our migration will then fail with an unintuitive error message: NoMethodError: undefined method `accessor' for #

We make our modifications in the migration, and try to re-run migrate.

For some reason, we decide to revert the migration to change something.

We then add in the model the rails line allowing this hstore to store “JSON attributes” i.e.: store :hstore_column_name, accessors:.

We successfully create an hstore (as :text) in the DB, and migrated.

Working with Rails’ JSON store is remarkably easy and convenient, but requires great care to make migration reversible to prevent frustration.Ĭonsider the following case, where the chronology is important: Extra Tip 3: Migrating with Rails’ JSON Store The method you are calling in this migration might not run the same way, or exist anymore, which will prevent any new-comer to your project to run the migration set of the project smoothly. Using methods coming directly from your models can seem like a good idea at first to DRY your code, but with time and commits your model will change.

If you need to use any kind of more advanced logic in your migration, define the methods you need in your migration and call them from there. ⚠️⚠️ Remember to only use raw Ruby+Rails logic in your migrations and never use anything except attributes coming from your own models. The migration should be one-way and not blindly set values back to nil in the down direction to avoid losing data if you were to roll it back.ĭepending on your project, you could merge both migrations into one. Gives: class RemoveNameFromMerchant 'active'}) The migration file generated will contain the following line: remove_column :table_name, :column_nameįor instance: $ rails generate migration RemoveNameFromMerchant name:string Rails automatically generates this kind of migrations thanks to the command line generator: $ rails generate migration RemoveFieldNameFromTableName field_name:datatype I’m starting with a basic that’s actually in the docs before getting to the tougher ones: 1- One line migration to drop DB columns: Retro-update existing records’ when adding a new column ★★★.So let’s walk through 9 tricks for generators and migrations gathered from experience (and Stack Overflow 🙊).

At work at Forest Admin it’s our job to handle every possible DB schema, in Rails, NodeJS and others, which means we’ve come across a few variations already. But while the most common migrations are no-brainers, some of them are not -or not clearly- covered in the manual. Rails Migrations were introduced to be a convenient way to alter the database in a structured and organized manner, and effectively bring great consistency over time on a project.Īs Ruby on Rails developers (I’m assuming you are too 😘), we should be pretty familiar with Rails Migrations and the Rails generator.