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diff --git a/doc/development/single_table_inheritance.md b/doc/development/single_table_inheritance.md index c8d082e8a67..da8d48f2a42 100644 --- a/doc/development/single_table_inheritance.md +++ b/doc/development/single_table_inheritance.md @@ -1,63 +1,11 @@ --- -stage: Data Stores -group: Database -info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments +redirect_to: 'database/single_table_inheritance.md' +remove_date: '2022-11-06' --- -# Single Table Inheritance +This document was moved to [another location](database/single_table_inheritance.md). -**Summary:** don't use Single Table Inheritance (STI), use separate tables -instead. - -Rails makes it possible to have multiple models stored in the same table and map -these rows to the correct models using a `type` column. This can be used to for -example store two different types of SSH keys in the same table. - -While tempting to use one should avoid this at all costs for the same reasons as -outlined in the document ["Polymorphic Associations"](polymorphic_associations.md). - -## Solution - -The solution is very simple: just use a separate table for every type you'd -otherwise store in the same table. For example, instead of having a `keys` table -with `type` set to either `Key` or `DeployKey` you'd have two separate tables: -`keys` and `deploy_keys`. - -## In migrations - -Whenever a model is used in a migration, single table inheritance should be disabled. -Due to the way Rails loads associations (even in migrations), failing to disable STI -could result in loading unexpected code or associations which may cause unintended -side effects or failures during upgrades. - -```ruby -class SomeMigration < Gitlab::Database::Migration[2.0] - class Services < MigrationRecord - self.table_name = 'services' - self.inheritance_column = :_type_disabled - end - - def up - ... -``` - -If nothing needs to be added to the model other than disabling STI or `EachBatch`, -use the helper `define_batchable_model` instead of defining the class. -This ensures that the migration loads the columns for the migration in isolation, -and the helper disables STI by default. - -```ruby -class EnqueueSomeBackgroundMigration < Gitlab::Database::Migration[1.0] - disable_ddl_transaction! - - def up - define_batchable_model('services').select(:id).in_batches do |relation| - jobs = relation.pluck(:id).map do |id| - ['ExtractServicesUrl', [id]] - end - - BackgroundMigrationWorker.bulk_perform_async(jobs) - end - end - ... -``` +<!-- This redirect file can be deleted after <2022-11-06>. --> +<!-- Redirects that point to other docs in the same project expire in three months. --> +<!-- Redirects that point to docs in a different project or site (for example, link is not relative and starts with `https:`) expire in one year. --> +<!-- Before deletion, see: https://docs.gitlab.com/ee/development/documentation/redirects.html --> |