Rails migration remove index if exists. Follow answered Dec 9, 2013 at 20:31.
Rails migration remove index if exists In Rails 4. 3 Rails 6. The use case is to simplify the re-scaffold in development. 1 makes migrations smarter by providing a new change method. class RemoveUniqueFromCoursesName < ActiveRecord::Migration def change remove_index(:courses, :name) add_index(:courses, :name) end end Removes the column from the table definition. However, all The reason you are seeing that message is because the table already exists. If you’re doing a big ol’ query against a few hundred thousand rows of data, with the index, it’ll take a few seconds. REFERENCES When you declare a reference, you're simply saying to include a column whose values should match those of another table (and in Rails you also get some useful methods to navigate through the associated models). The foreign key will be named after the following pattern: fk_rails_<identifier>. ; Delete the migration file manually. Setting up and using Delegated Types. Future. The name of the file is of the form Adds a new foreign key. try removing the index before removing the column. With this change, To simplify these conditions, now Rails has added support for if_exists/if_not_exists on remove_column/add_column in migrations. The name of the file is of the form I usually: Perform a rake db:migrate VERSION=XXX on all environments, to the version before the one I want to delete. If you're not sure, you can run $ rake db:migrate:status. class AddUniqIndexToCompanyList < ActiveRecord::Migration[6. How is supposed to be named a drop table migration file and is there a remove_reference(table_name, ref_name, foreign_key: false, polymorphic: false, **options) public Removes the reference(s). tl;dr- you won't hurt anything really, but don't do that TRUNCATE anyway. The name of the file is of the form You have probably defined the index in your previous play with migrations. establish_connection("schema_migrations_#{Rails. rb or structure. After that you can safely delete the migration file. To migrate to a particular version, use: rake db:migrate:down VERSION=20080906120000 If you want to quickly apply a table drop, you could create a new migration, run it, then delete it along with the original migration you no longer want. connection end [Using Rails 5] Generate migration: rails generate migration add_user_reference_to_uploads user:references This will create the migration file: class AddUserReferenceToUploads < ActiveRecord::Migration[5. The following options are supported by the PostgreSQL adapter in addition to the common index options. One common task that you may need to do as part of a database migration is removing So, we scrambled to properly migrate the ones that were up in the first place, and then proceeded to resolve the two failing migrations. Moreover who could I rely on such method of the rails framework when the remode_index is not able to basically remove an index just by its name (without even managing any schema; as PostgreSQL cares about it). What else could be wrong? After that, I was able to delete they dummy migrations and have a clean migration status :) Another alternative is deleting the missing files from the database directly (rails dbconsole): delete from schema_migrations where version='<MIGRATION_ID>'; remove_index:accounts,:branch_id, name::by_branch_party. identifier is a 10 character long string which is deterministically generated from the from_table and column. It’s a solution to the common problem of adding a field to make a new then correct your migration file (removing add_index line) and run migration again. It generates the following code: class AddPartNumberToProducts < ActiveRecord::Migration[6. It determines, based on the timestamp of the migration file and comparing it with its internal You can use: rails db:rollback STEP=<put the number of migrations you want to go back. execute 'drop table if exists campaigns' end If I remove index: true, foreign_key: CreateActioncodes is to be run first thereby ensuring that the action codes table exists. 2) - 6 notes # Allows you to specify indices to add in a migration that will only be created if they do not # already exist, or to remove indices only if column_exists?(table_name, column_name, type = nil, **options) public Adds a new foreign key. how to implement an if entry exist overwrite rails database. 0] def change reversible do | direction | direction. rails generate migration add_index_to_users_email simply creates an empty migration file and did not describe a index. Declare associations between Active Record models. 0. The name of the file is of the form YYYYMMDDHHMMSS_create_products. So in your case, class CreateNewTeams < ActiveRecord::Migration def self. 3. index in rails migrations. We want it to default to false for new users, but existing users are considered to have already opted in, so we use the User After creating a migration file with rails generate migration AddClientToUser I can edit my migration file like so: class AddClientToUser < ActiveRecord::Migration def self. Create new migration file with empty change method: $ rails generate migration add_index_in_users_on_name Add call of add_index method to empty change method: add_index :users, 'lower(name)', name: 'index_users_on_lower_name', unique: true Run Rake I have the following migration class LinkDoctorsAndSpecializations < ActiveRecord::Migration def up add_reference :doctors, :doctor_specialization, polymorphic Firstly, create a migration to add a reference of the Roles table to the Users table: rails generate migration AddRoleRefToUsers role:references This will create a migration file that contains the following: class AddRoleRefToUsers < ActiveRecord::Migration[6. index {|col| col. # e. But than just removed index definition from migrations. Then I realized I needed to rename the table to 2 Creating a Migration 2. class Removing tables - Safe. remove_index:accounts,:branch_id, name: :by_branch_party. But to be sure, I'll suggest to re-run migrations: db:migrate:reset, which will The add_foreign_key command in your schema gave your foreign key the name notifications_on_conversation_id. integer:role, null: false t. index creation; PostgreSQL includes a variety of index options. I keep validating existence in request rules. ️ Use : but does not exist yet. class RemoveSettingsReportColumnsFromCompany < ActiveRecord::Migration Active Record AssociationsThis guide covers the association features of Active Record. I used rails generate migration AddActioncodeToOrganizations actioncode: The generated file with its contents is just a starting point, and you can add or remove from it as you see fit by editing the db/migrate/YYYYMMDDHHMMSS_create_products. Will silently ignore indexes that don’t exist. So you can have use something like this: return queryInterface. 1 added support for if_not_exists option to add_index. Defaults to false. All is well on my local version but I cant I need to remove a foreign key from a table with migrations. It can be helpful to provide these in a migration’s change method so it can be reverted. :if_exists. Migrations are stored as files in the db/migrate directory, one for each migration class. In this other SO answer: How to remove index in rails, that is why it is not being updated so you can try deleting the migrations which are throwing errors and then running rails db:migrate, if The generated file with its contents is just a starting point, and you can add or remove from it as you see fit by editing the db/migrate/YYYYMMDDHHMMSS_create_products. rb) by calling rake db:drop db:create db:migrate. rb, that is to say a Then you can run $ rake db:migrate again, and the migrations should run successfully. The name of the For the migration to be reversible, you now (Rails 6+) need to use the :column option. migration do up do create_table :user_settings do primary_key :id String :signature, null: true, text: true end alter_table Index name 'index_authorizations_on_user_id' on table 'authorizations' already exists ArgumentError: Index name 'index_authorizations_on_user_id' on table 'authorizations' see if any indexes exist that should also be dropped. 0] def change end end If you want to add/remove columns or index to a table, use the add_column, remove_column, and add_index methods. If your latest migration updated the schema correctly, you could just run rake db: reset, which will recreate the database and then load from the schema. class RemoveGenreFromBooks < ActiveRecord::Migration def change remove_reference :books, :genre, index:true, foreign_key: true end end In summary, Rails migrations are a powerful tool for modifying the database schema of your application. The question focuses on custom sql migration generation, not manually adding migration operations like Sql(). class Order < ActiveRecord::Base end def up add_column :orders, :payment_type, :string Order. remove_index(table_name, column: column_name): Removes the index specified by column_name. The timestamps macro adds two columns, created_at and updated_at. After reading this guide, you will know how to: Understand the various types of associations. I ran my migrations, then ran `rails db:migrate:redo` to When migrating it calls the add_column command with if_not_exists: true argument. Adding unique: true also ensures rolling back the migration will recreate the index with the uniqueness constraint (barring problematic data being inserted in the meantime). ActiveRecord: Update a record if exists else create? 0. I migrated the database and removed the tsvector column from model Post (and added it to Message). remove_index :actions, :column => [:user_id,:action_name] or by name, a worse That's odd; that index shouldn't exist already because the migrations failed. ActiveRecord::Migration. 2, when creating a table or adding a reference via references or add_reference how do you specify that the foreign key should cascade on delete. rb file gets changed Sequelize has removeConstraint() method if you want to remove the constraint. Delete add_column line and run the migration. The options hash can include the following keys: You have probably defined the index in your previous play with migrations. Just know that if you modify the enum type, all tables using it will of course be influenced in the range of possible values. After a few minutes of figuring out how to remove an index, @ben figured out how to do it via Rails console. When you want to add a new column to an existing table in your database, you can use a migration with the format "AddColumnToTable" followed by a list of column names and types. Remove the reference remove_reference (:products,:user, index: true) Remove The database schema evolves continuously. Commit your code, deploy it to production, . Here's how to understand the problem: You have existing users without email values (users table has no email attribute). The mysql query. Checks if the index exists before trying to remove it. class AddUsers < ActiveRecord:: Migration [5. If it is true you have 2 options: The simplier one (works if you code is not in production). Rails and database: find entry if exists else create. Removing indexes - Safe. In the following example, the new column published will be given My approach to this will be migrate first, then rollback. Groups", "Name"); However I get the message: Cannot drop the index 'dbo. :force. rb I see that column should be unique, in postgres I dont see it as unique. If the database supports multiple indexes per table, and at least most do, then you can create each of them through t. 1 Returns true if a record exists in the table that matches the id or conditions given, or false otherwise. ; Write a migration that adds columns: provider & uid. reset_column_information Adds a new foreign key. The index is already created when using references, a foreign key constraint is also added when using foreign_key but the index is created regardless (unless you pass index: false). You can recreate database from scratch using migrations (not from db/schema. Therefore we often get the errors like column already exists or doesn’t To avoid above issues and to keep things consistent, Rails team added support to pass if_exists/if_not_exists options to remove_foreign_key/add_foreign_key. 3. 3 Adding Columns. This is the safest way to add uniqueness constraints into existing indexes This can include creating new tables, modifying existing tables, and deleting tables. rb, that is to say a UTC timestamp identifying the migration followed by an underscore followed by the name of the migration. Depending on what SQL you're using and how it's configured it might be a problem. Creating indexes - Safe only for readonly models - Otherwise make sure you create indexes concurrently. This method is preferred for writing constructive migrations (adding I have a table with a compound index that wasn't created through a rails migration. No additional CREATE TYPE or DROP TYPE in the migration. remove_reference(table_name, ref_name, foreign_key: false, polymorphic: false, **options) public Removes the reference(s). So the procedure is as following. my files - class AddViewsToBlogPost < ActiveRecord::Migration[7. The argument can take five forms: Integer - Finds the record with this primary key. However the migrations are still there and if you run rails db:migrate you are still gonna I have removed a column (called day_rate) that I added to one table (client_fees) and added it to another (clients) in my rails app. Migrations of that kind should raise an ActiveRecord bin/rails generate migration AddPartNumberToProducts. reset_column_information I have a company table and I want to check the existence of multiple column to remove them. If the version specified does not exist, Rails will throw an exception. As there is a method to add a referecen, there is a one to remove also - remove_reference Syntax is: remove_reference(table_name, ref_name, options = {}) So in your case, to remove the reference of Genre:. Now i want run the rails project in another system for that i need the migration files to create the table. 2. Irreversible transformations. #remove_reference and #remove_belongs_to are acceptable. 3 2 Generating Migrations 2. If the hidden purpose of your question is to DROP the index before making INSERT to a large table, then this is a useful one-liner:. For Rails 4. 4. Roll down a number(n) of recent migrations: rake db:rollback STEP=n. 0] Do a crosscheck in the db if that exists like as shown (there are many tools available). Use Single Table Inheritance. So your remove_foreign_key command must specify the existing foreign key name instead of the Just delete the offending migration and get on with more interesting things. rename :uuid, This migration adds a receive_newsletter column to the users table. The foreign key will be named after the following pattern: So, I created a migration by setting the users table (--table=users) and placed the removal of the constraint, but then I redid the action for possible new inclusion needs. This is quite as simple as running a migration. up drop_table :teams create_table :teams do |f| # new purpose end end def self. I ran my migrations, then ran `rails db:migrate:redo` to rollback the migration and redo it, and my schema. your options are either edit that migration to add the foreign key, then comment that migration, migrate down, add your remove_foreign_key code and migrate:up or run rails db:reset and loose all data or manually I'm running Postgres version 9. up A feature that Rails 6. When you delete migration files in the db/migrate/ directory, any environment where bin/rails db:migrate was run when those files still existed will hold a reference to the migration Used to specify an operation that is only run when migrating up (for example, populating a new column with its initial values). Rails migrations is a powerful and flexible way to update the schema without dropping and re-creating the database. remove_index :order_items, :order_id remove_column :order_items, :order_id add_reference :order_items, :order, foreign_key: true # or add only the foreign the key constraint # i'm afraid it I would miss anything else doing so Rails Migration with rails, deleting record if exists with a same column value before creating a new record. For instance, if you want to remove the Users Table write a command line statement like this: rails generate migration DropUsersTable. remove_index "jasa_images", name: "index_jasa_images_on_jasa_id" then, you can add a new index in the migration file ' already exists while running rails db:migrate. The order in which migrations are run is based on the time stamp of the migration - as indicated in the name of the file. your options are either edit that The migration will be executed on production environment, but will have no effect on your database. if you write a migration on Rails 6. The type and options parameters will be ignored if present. timestamps end 2 Creating a Migration 2. Rails comes with a method called column_exists? This migration adds a table called products with a string column called name and a text column called description. Set to :cascade to drop dependent objects as well. There are ways around this on the database level (e. The if_not_exists provided to create_table also gets propagated to all indexes getting created in the I have the following migration: Sequel. (remove_index :books, :author_id) – Novae. Command to generate scaffold: rails g scaffold Child parent:references name:string Resulting migration: 2 Creating a Migration 2. A quick look at setting a unique index for one or more column. This option is supported from Rails 6 onwards so you need to be using Rails 6 to use it 😄. This will generate the empty . 0] def change add_reference :users, :role, null: false, foreign_key: true end end Now I want to remove existing Unique key with next migration's Down() method by using: DropIndex("dbo. ActiveRecord default indexes. Marek Lipka Marek Use Rails Migrations to delete an index without knowing its name. Do a db:reset. Later on, delete the migration, push the code to production. I have a company table and I want to check the existence of multiple column to remove them. one that actaully adds the field and then I would run it using the down syntax to remove the field. Rails automatically generates migration, thanks to the command line generator. This will ensure that Rails will attempt to create the table only if it does not exist already. , triggers, or a computed column; see link text). Looks like your migrations are out of sync as you say. – 2 Creating a Migration 2. down do # Remove unique index execute <<-SQL DROP INDEX IF EXISTS unique_user_role_in_project; SQL end end create_table:users do | t | t. When rollbacking the migration it should call remove_column with the argument To expand on @showaltb's great answer, here is a complete migration to remove all indexes on a table, without knowing their names: remove_index 'tablename', name: index. The foreign key will be named after the following pattern: but no foreign_key_exists? There is foreign_key_exists?:) Checks to see if a foreign key exists on a table for a given foreign key definition. The name of the Adds a new foreign key. from_table is the table with the key column, to_table contains the referenced primary key. Here, the execute method accepts a string of native SQL query and then runs it on the database. You could It’s rather convenient using if_exists option for drop_table method in migrations. If all migrations are "up," then your migrations have run successfully. This method is preferred for writing constructive migrations (adding rails generate migration add_index_to_table_name column_name:uniq username, :string add_index :moderators, :username, unique: true end end If you're adding an index to an existing column, remove or comment the add_column line, or put in a check. The code is as follows (up and down methods Hrm I'm not sure what we should do here, because technically if_exists: true wouldn't apply to the reverse of drop_table - it'd be create_table and you'd never want create_table :table_name, if_exists: true. 1, then upgrade to Rails 7, the migration should do the Definitely not the cleanest answer, but I had the same issue as you and I just added the missing index as the first line of the migration: 2 Creating a Migration 2. remove_index:accounts, if_exists: true. Deleting a migration file doesn't undo the change: it won't remove the two of those This migration adds a table called products with a string column called name and a text column called description. integer:project_id, null: false t. The syntax for dropping a table is: drop_table :table_name @user1229490 If there are any restrictions on number of indexes, they would be imposed by your database; not by rails. Then I realized I needed to rename the table to So, we scrambled to properly migrate the ones that were up in the first place, and then proceeded to resolve the two failing migrations. One situation where you might have to use execute is if Rails has added an index and named it according to the table name, then you've renamed the table. git rm path/to/offending/migration git commit -m "removed unneeded migration" (assuming you're using commit because heroku likes deploying with git push) it won't be in the schema_migrations table if it's failed to run every time so you don't need to delete it from there. But I Introducing: Migration Builder. remove_index :profile_pictures, column: :picture_id, unique: true add_index :profile_pictures, :picture_id $ rails generate migration AddPartNumberToProducts part_number:string:index. 65. The name of the file is of the form 2 Generating Migrations 2. In that case, type and options will be used by #add_column. These special columns are automatically managed by Active Record if they exist. Once the migration has reached production it doesn't change. Quick Fix A quick fix is to remove the hstore declaration in the model and to migrate, then re-add it. add_column To clarify, inside a migration the syntax to remove a 2 column index is the following. It’s a command-line tool that prompts you for the change you want to make (add column, remove column, create table, drop In Rails it is possible to do: add_index :table, :column_name, :using => 'btree' Is it possible in Rails 4 with PGSQL to add a GIN or GiST index like: add_index :students, :name, $ rails d migration RemoveColumnsFromAuthors remove db/migrate/20210725132852_remove_something_from_authors. The best way to cover both bases is to add a conditional into the migration. timestamps end class ExpandEnclosureUrl < ActiveRecord::Migration def up # remove index cuz we need to remove_index :scraped_episodes, :enclosureUrl # change length to 2048 characters change_column :scraped_episodes, :enclosureUrl, :text, :limit=>2048 # redo this index to only index the first 255 chars add_index :scraped_episodes, :enclosureUrl, :length See how we remove an index, then add it? This means if the migration fails while adding the new index, and we have to re-run the migration, we’re now executing the query without an index on the favorite_colors column. remove :id t. 2 with Rails. Add uniqueness index. Another question : why a method remove_index using the name of the index as parameter would need and tablename to remove the index ? We use the same migration and rescaffold it when changes are made. For example, I created users_roles and did a migration to add an index, which Rails named index_users_roles_on_role_id. will give you back all of the indexes on the table, however it includes additional info other than just the names. I have deleted the migration files in rails project. Marek Lipka Marek tl;dr- you won't hurt anything really, but don't do that TRUNCATE anyway. # Checks to see if a foreign key exists. Commented Feb method `remove_colmun' in Rails This migration adds a receive_newsletter column to the users table. Although this command ignores most options and the block if one is given, it can be helpful to provide these in a migration’s change method so it can be reverted. remove_index:accounts, name: :by_branch_party, algorithm: :concurrently I have the following migration: Sequel. 2, create case-insensitive unique index in users table on name column. Choose the right association type for your models. First, this command will check whether the migration exists and if it has already been performed and if so, it will do nothing. Also removes a type column if one exists. This name is different than the default name that foreigner would normally assign based on the column name, which is notifications_conversation_id_fk. This is the table where I have the foreign key: class CreatePriceWorkshops < ActiveRecord::Migration def change # This file exists to ensure that old migrations run the same way they did before a Rails upgrade. Since you already have a status enum type from your previous model, the solution is extremely easy and straightforward: just specify the type as :status and you're good to go. When you run bin/rails db:migrate, Rails does not re-run all migrations. This migration script will add a new exclusion constraint sales_orders_non_deleted_date_unique on the table sales_orders. In the case described you could have issued rails generate migration AddIndexIdToTable index_id:integer:index command and then delete add_column line from the generated migration. If you revert this migration, even if you specify the column type (like :integer), it will NOT re-add the index on the column, which can bring you a Write a migration that adds columns: provider & uid. If you really don't want to delete the migration, you can rewrite it using raw SQL: def up connection. Make sure that your migration timestamps corresponds with the data in this column. To migrate from default id to use uuid, I think you could something similar to what I had: class ChangeVocBrandsPrimaryKey < ActiveRecord::Migration def change add_column :voc_brands, :uuid, :uuid, default: "uuid_generate_v4()", null: false change_table :voc_brands do |t| t. Provide details and share your research! But avoid . 1 Creating a Standalone Migration. A primary key column called id will also be added implicitly, as it's the default primary key for all Active Record models. X, you can check the existence of columns with the following: columns("[table-name]"). You can then add this into that empty class RemoveArticleIdFromComment < ActiveRecord::Migration[6. After a few minutes of figuring out how to see if any indexes exist that should also be dropped. 4. Take a look at the documentation here: http://apidock. rb $ rails d migration In MySQL, uniqueness is enforced only at the table level. Active Record Migrations. Commit your code, deploy it to production, and run the migration there. The name of the Depending on what SQL you're using and how it's configured it might be a problem. com/rails/ActiveRecord/ConnectionAdapters/SchemaStatements/index_exists%3F In few applications, we have migrations to remove index where we don’t want to raise an error if an index was already removed. One more cool thing about this option is that adds the check for whether the table exists in database or not in SQL instead of checking it via Ruby code. If you have deleted an older migration, delete the corresponding timestamp. rb file gets changed and its version is set to the timestamp on the last migration that was run. Name', because it does not exist or you do not have permission. g. Migrations can manage the evolution of a schema used by several physical databases. 46. This This migration will remove the category column from the events table, add a new string column events_type and a new boolean column active with the default value of false. so this would be more appropriate rails generate migration AddIndexToUsers email:string:index should give you index_exists?(table_name, column_name, **options) public Checks to see if an index exists on a table for a given index definition. I In a test app, I've created a migration to add a column with an index, then later I remove the column without removing the index. After testing in development, the commands needed were: The add_foreign_key command in your schema gave your foreign key the name notifications_on_conversation_id. schema. 1] def change add_reference :uploads, :user, foreign_key: true end end As you just want to set values for all existing records, you can use update_all, which is much faster than looping over all instances of order, as it uses just database statements and doesn't instanciate all the orders:. Removes the index on branch_id in the accounts table if exactly one such index exists. Instead you can use execute to create the index with SQL:. Thanks for contributing an answer to Stack Overflow! Please be sure to answer the question. execute <<-SQL CREATE INDEX temporary_events_campaign_tinfoid_date_messagetype ON This indeed works, but there's a HUGE caveat here: if you are removing a column that contains a reference (like user_id), you probably have an index on that column, which will be automatically removed by Rails 4+ on remove_column. we can have indexes on varchars, but we can’t have any on text. rb file. removeConstraint('users', 'users_userId_key', {}) you are trying to remove the foreign_key from table groups, but if you check in your psql database the table groups does not have that foreign key. The name of the remove_index:accounts,:branch_id, name: :by_branch_party. This migration fixed it: def change execute <<-SQL DROP INDEX IF EXISTS index_posts_tsv_body; DROP TRIGGER IF EXISTS tsvectorpostupdate ON posts; SQL end Share Your down should leave the database in the state before the migration was run. Roll down to a previous, specific version: $ rake db:migrate:down VERSION=nnn # Rails 3 (provide version number class AddUsers < ActiveRecord:: Migration [5. Set to true to only drop the table if it exists. unless index_exists?(:content_pages, :parent_id) add_index(:content_pages, :parent_id) end As a last phase of development (not recommended once in production), you can clear out the schema_migrations table, consolidate your migrations (one-to-one with classes) and create a new table (beware: running migrate has different behaviours, depending on mysql vs postgresql) @david-lowenfels answer is perfect for this context. So your remove_foreign_key command must specify the existing foreign key name instead of the It means, once add_index/remove_index is failed in a migration, the migration is marked as fail, but the commands before add_index/remove_index is executed and commited! In next time we call db:migrate, rails try to run this migration again because it was marked as failed, but rails cannnot create users table because it's already exist. This can happen if a migration partially ran before (creating the index) but didn't complete for some reason, or if there's a previous migration that created the same index. remove_column (:suppliers,:qualification). (and drop if_not_exists: true when reversing a create_table. 2 Creating a Migration 2. Now, generally this is not a huge cause for concern, but the migrations still needs to complete. What happens when you write a migration is that the db/schema. 1. The name of the As there is a method to add a referecen, there is a one to remove also - remove_reference Syntax is: remove_reference(table_name, ref_name, options = {}) So in your case, to remove the reference of Genre:. We want it to default to false for new users, but existing users are considered to have already opted in, so we use the User model to set the flag to true for existing users. Now, I need to create a rails migration that will delete this index and create a new one, but I don't necessarily know what the name of the index will be. Follow answered Dec 9, 2013 at 20:31. Don't run the migration on your local, and running it won't make any sense. you are trying to remove the foreign_key from table groups, but if you check in your psql database the table groups does not have that foreign key. search the application for that field name; see if there's an existing rails migration that you can use to DOWN the change; Finally, I would consider creating a change migration as normal, i. 2 The built-in ActiveRecord method for creating indexes (add_index) does not support functions or any other more advanced features. migration do up do create_table :user_settings do primary_key :id String :signature, null: true, text: true end alter_table :user_settings do add_foreign_key :user_id, :users, null: false, on_delete: :cascade add_index :user_id end end down do drop_table :user_settings end end I had the same problem as yours. Depending on the database you’re using, indexes using this column may be This migration adds a table called products with a string column called name and a text column called description. ; Replace It means, once add_index/remove_index is failed in a migration, the migration is marked as fail, but the commands before add_index/remove_index is executed and commited! In next time we call db:migrate, rails try to run this migration again because it was marked as failed, but rails cannnot create users table because it's already exist. 1 added was the ability to use :if_not_exists and :if_exists. please tell me how to 2 Creating a Migration 2. remove_index:accounts, name: :by_branch_party, algorithm: :concurrently If want to remove the index too, you do with migration too: rails g migration remove_post_id_from_comments post_id:integer:index migration file: class RemovePostIdFromComments < ActiveRecord::Migration def change remove_index :comments, :post_id remove_column :comments, :post_id, :integer end end then run: rake db:migrate I think unique will be removed if you remove the old index and add it again. 0] def change add_column :bar, :foo, :string, if_not_exists: true end end Expected behavior When migrating it calls the add_column command with if_not_exists: true argument class AddUniqeConstraintToShipments < ActiveRecord::Migration def up execute <<-SQL alter table shipments add constraint shipment_tracking_number unique (tracking_number, carrier); SQL end def down execute <<-SQL alter table shipments drop constraint if exists shipment_tracking_number; SQL end end 2 Creating a Migration 2. name. The add_index method can be used to add indexes to improve the performance of your queries, and migrations can be then correct your migration file (removing add_index line) and run migration again. The migration files exists so Drops a table from the database. A custom name can be specified with the :name option. If there are pending migrations Justin Wood's answer should work, but with one change: replace the column name in the remove_index method with the name of the index: remove_index :student_contexts, Also removes a type column if one exists. You can use the index_exists? method within your migration to test whether the index you need to remove is actually there. In that case, options and the block will 2 Creating a Migration 2. If it is true you have 2 options: The simplier one (works if you When generating migrations make sure to use either snakecase or camelcase to make the name readable rails g migration AddTrigramIndexLocationToUsers or rails g To migrate to a particular version, use: rake db:migrate:down VERSION=20080906120000 If you want to quickly apply a table drop, you could create a new edit: I tried also SQL code in migration but same result, in schema. I'm running Postgres version 9. class RemoveGenreFromBooks < ActiveRecord::Migration def change remove_reference :books, :genre, index:true, foreign_key: true end end As you just want to set values for all existing records, you can use update_all, which is much faster than looping over all instances of order, as it uses just database statements and doesn't instanciate all the orders:. 1] def change remove_column :comments, :article_id, :string, if_exists: true end end Great! You just completed a post! This migration adds a receive_newsletter column to the users table. Asking for help, clarification, or responding to other answers. search the application for that field name; see if there's an existing rails migration that you can use to DOWN the change; The generated file with its contents is just a starting point, and you can add or remove from it as you see fit by editing the db/migrate/YYYYMMDDHHMMSS_create_products. class RemoveUniqueFromCoursesName < ActiveRecord::Migration def change remove_index(:courses, :name) add_index(:courses, :name) end end as @spickermann noted, just delete the migration. However, all this power and flexibility can be overwhelming. DROP INDEX IF EXISTS [IndexName] ON [dbo]. add_index :contact, [:survey_id, :voter_id], :unique=> true Check if record exists in Rails before creating. Either you can put the index code in a conditional block like this. Let’s 3 Indexing. Some transformations are destructive in a manner that cannot be reversed. string:name, null: false t. 2 In a test app, I've created a migration to add a column with an index, then later I remove the column without removing the index. Improve this answer. You could address this on an application level and put in a validation that checks for uniqueness if the product_id is not null. Groups. The name of the In case you've messed up your migration and it's a local database, it's always easiest to just drop the database and run migrations again. name == "[column-name]"} If it returns nil, no such column exists. But I'd rather recommended to undo the initial migration and add reference instead: index_exists?(table_name, column_name, options = {}) public Checks to see if an index exists on a table for a given index definition. SHOW INDEXES FROM persons. Index name 'index_books_on_author_id' on table 'books' does not exist – Tony. Commented Feb 14, 2013 at 20:15. Share. Migration Builder is exactly that. The <<~ squiggly symbol is a plain ruby syntax for writing long multi-line indented content. your generator. rb seems OK. I'm using connection string that assumes I'm DBO. add_column :moderators, :username, :string unless column_exists? :moderators, :username class AddLockableToUsers < ActiveRecord::Migration def connection # Connect database where schema_migrations table can be found puts schema_migrations_table_name @connection = ActiveRecord::Base. class RemoveSettingsReportColumnsFromCompany < ActiveRecord::Migration I think unique will be removed if you remove the old index and add it again. def change. Removes the index named by_branch_party in the accounts table concurrently. Indexes, foreign keys and foreign keys constraints are strictly related concepts in databases that are often confused or misunderstood. If it You can't simply run drop_table :table_name, instead you can create an empty migration by running: rails g migration DropInstalls. Basically it runs the migrations that have not run yet, for the Do we need to do it thru EntityFramework CodeFirst Migration, or can we just run a script to drop the index ? If we need to drop the index thru EntityFramework CodeFirst Ruby on Rails latest stable (v7. But I used it only because of the softDeletes, be careful with your business rules. Unfortunately, this option is not allowed for remove_column, but can be implemented for When `column` is passed as an array and the column does not exist, then `index_exists?` check would fail to return early which would cause `index_name_for_remove` For Rails 2. $ we write migrations using methods like add_column for adding column and remove_column for removing a column. That's why your migrations work in the latter and not the former: you have two indexes with the same name on different However, some database constraint in rails can be tricky. The database schema evolves continuously. Commented Feb method `remove_colmun' in Rails The mysql query. Rails 3. Rails 6. The two choices are: Delete the if_exists: true option when running a reverse. Clearly there's no "create table" migration for that table so the "drop table" migration has no right to exist. You should add first a database index to force this condition at the lowest level as possible: add_index :contacts, [:voter_id, :survey_id], unique: true Create a migration and add a composite unique key to survey_id, voter_id. 1 adds a feature, where we can now Removes the index on branch_id and party_id in the accounts table if exactly one such index exists. I know that it is possible to get a list of table names and column names within a migration step. rb file in /db/migrate/ that still needs to be filled to drop the “Users” table in this case. remove_index(table_name, name: index_name): Removes the index specified by index_name. ActiveRecord::ConnectionAdapters::SchemaStatements#add_reference:. 1] def up execute <<-SQL DROP INDEX IF EXISTS index_company_lists_on_company_id; CREATE UNIQUE INDEX I believe there are three options available for reverting migrations (they also overlap): Roll down the most recent migration: rake db:migrate:down # Rails 2 only. Hot Network Questions How to re-orientate a mesh with messed up world co-ordinates Romans 11:26 reads “In this way all of Israel will be saved;” but So, I created a migration by setting the users table (--table=users) and placed the removal of the constraint, but then I redid the action for possible new inclusion needs. down drop_table :teams create_table :teams do |f| # old purpose end end end This field is used by Rails to check whether migrations are up to date. e. Drops a table from the database. This migration fixed it: def change execute <<-SQL DROP INDEX IF EXISTS index_posts_tsv_body; DROP TRIGGER IF EXISTS tsvectorpostupdate ON posts; SQL end Share edit: I tried also SQL code in migration but same result, in schema. Here's a handy cheatsheet for most common migration operations. remove_index :accounts , column : [ :branch_id , :party_id ] Removes the index named remove_index(table_name, options = {}) public Removes the given index from the table. . rails db:migrate rails db rollback rm If it's the existing index then you may need to do more than that: Delete duplicated data. Ruby calls it "Here Documents" or heredocs in short. This allow us to generate or remove a column or table if it was or wasn’t already present in the database. sql (depending on what you use) will be aligned. The name of the Do a crosscheck in the db if that exists like as shown (there are many tools available). remove_index :order_items, :order_id remove_column :order_items, :order_id add_reference :order_items, :order, foreign_key: true # or add only the foreign the key constraint # i'm afraid it I would miss anything else doing so Rails Migration with Ruby-on-Rails migrations were introduced to be a convenient way to alter a database in a way that is both structured and organized. Some major database systems do not allow a unique index to contain multiple NULLs: unique applies to NULLs as well as non-NULLs. Steps to reproduce class AddFooToBar < ActiveRecord::Migration[7. rake db:migrate doesn't drop the table. env}"). remove_index:accounts, name::by_branch_party, algorithm::concurrently I want to delete a table in my rails app but i cannot use rollback, because i created this table a long time ago, and i have a LOT of other tables created since that one. In that case, options and the block will bin/rails generate migration AddPartNumberToProducts. [TableName] This syntax has been available since SQL Server 2016. kklemayfauxaexgchiqiueafvctidajspjwcoczayyngveghkjipcs