[RUBY] What to do when an error (StandardError: An error has occurred, this and all later migrations canceled:) appears in rails db: migrate

Introduction

This will be a memo for learning.

This time, we will deal with the error that occurs after executing $ rails db: migrate or $ rails db: migrate.

== 20200107095832 CreateMicroposts: migrating =================================
-- create_table(:microposts)
rails aborted!
StandardError: An error has occurred, this and all later migrations canceled:

SQLite3::SQLException: table "microposts" already exists: CREATE TABLE "microposts" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "content" text, "user_id" integer, "created_at" datetime NOT NULL, "updated_at" datetime NOT NULL)

Continued below

Cause

I think there is something wrong with the migration of the command I did last time. Probably an error occurred in the middle of the migration process and the table was generated, but the migration that generated the table remains unexecuted. Is it in such a state? I think

solution

①

$ rails db:migrate:reset

After resetting the database

$ rails db:migrate

Migrate again

This command is used when you want to delete the database, modify the new migration file, and perform migration again.

②

$ rails db:migrate:reset

An error occurs after resetting the database!

ActiveRecord::NoEnvironmentInSchemaError: 

Environment data not found in the schema. To resolve this issue, run: 

        bin/rails db:environment:set RAILS_ENV=development


Tasks: TOP => db:migrate:reset => db:drop => db:check_protected_environments
(See full trace by running task with --trace)

Coping

rake db:migrate:status

Check the status of db with the above command. ⬇︎ Execution content

 up     20201013130002  Devise create users
 down    20201015132219  Add devise to users

Apparently, the migration file at the bottom is suspicious. .. .. I checked the editor I created the same migration file twice. .. So, let's delete the migration file at the bottom.

• If it is down, there is no problem even if you delete the file manually.

$ rm -rf db/migrate/20201015132219_add_devise_to_users.rb

This will migrate again. ⬇︎ Execution result

== 20201013130002 DeviseCreateUsers: migrating ================================
-- create_table(:users)
   -> 0.0061s
-- add_index(:users, :email, {:unique=>true})
   -> 0.0014s
-- add_index(:users, :reset_password_token, {:unique=>true})
   -> 0.0011s
== 20201013130002 DeviseCreateUsers: migrated (0.0087s) =======================

I was able to do it without any problems!

Finally

This time I learned about errors when migrating. DB reset did not solve the problem. The cause was a duplicate migration file.

I would appreciate it if you could point out any mistakes.