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PORemove rails model after migration
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copied!<p>It seems strange to me, that creation of model, running migration, destroying it, and creating again same model reports SQL exception:</p> <pre><code>project|master ⇒ rails g model name name invoke active_record create db/migrate/20130417185814_create_names.rb create app/models/name.rb project|master⚡ ⇒ rake db:migrate == CreateNames: migrating ==================================================== -- create_table(:names) -> 0.0020s == CreateNames: migrated (0.0021s) =========================================== project|master⚡ ⇒ rails d model name invoke active_record remove db/migrate/20130417185814_create_names.rb remove app/models/name.rb project|master⚡ ⇒ rake db:migrate project|master⚡ ⇒ rails g model name test invoke active_record create db/migrate/20130417185845_create_names.rb create app/models/name.rb project|master⚡ ⇒ rake db:migrate == CreateNames: migrating ==================================================== -- create_table(:names) rake aborted! An error has occurred, this and all later migrations canceled: SQLite3::SQLException: table "names" already exists: CREATE TABLE "names" ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, "test" varchar(255), "created_at" datetime NOT NULL, "updated_at" datetime NOT NULL) /path/project/db/migrate/20130417185845_create_names.rb:3:in `change' -- create_table("names", {:force=>true}) -> 0.0100s -- initialize_schema_migrations_table() -> 0.0025s -- assume_migrated_upto_version(20130417185814, ["/path/project/db/migrate"]) -> 0.0010s You have 1 pending migrations: 20130417185845 CreateNames Run `rake db:migrate` to update your database then try again. </code></pre> <p>Maybe, I doing something wrong? Migration has code for deleting table - does it may be used only for rollback?</p> <h1>Solution</h1> <p>Delete model and database table and generate a new one is pretty easy:</p> <ol> <li>Create model: <code>rails g model user name</code></li> <li>Do migrations: <code>rake db:migrate</code></li> <li>Implement something, suddenly remember that you need to delete model</li> <li>Revert specific migration: <code>rake db:migrate:down VERSION=20130417185814</code>, where <code>20130417185814</code> is migration id (can be seen in rake db:migrate:status)</li> <li>Remove model: <code>rails d model user</code></li> <li>Suddenly remember that you need this model, but with other fields</li> <li>Create model: <code>rails g model user email group:references</code></li> <li>Successfully migrate database: <code>rake db:migrate</code></li> </ol>

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