Merge branch 'ee-52442-minimal-remove-mysql-support' into 'master'

EE port of "Only support postgresql (minimal version)"

See merge request gitlab-org/gitlab-ee!14239

.gitlab-ci.yml

 image: "dev.gitlab.org:5005/gitlab/gitlab-build-images:ruby-2.6.3-golang-1.11-git-2.21-chrome-73.0-node-12.x-yarn-1.16-postgresql-9.6-graphicsmagick-1.3.29"
 
 variables:
-  MYSQL_ALLOW_EMPTY_PASSWORD: "1"
   RAILS_ENV: "test"
   NODE_ENV: "test"
   SIMPLECOV: "true"

.gitlab/ci/rails.gitlab-ci.yml

@@ -10,11 +10,6 @@
       command: ["postgres", "-c", "fsync=off", "-c", "synchronous_commit=off", "-c", "full_page_writes=off"]
     - name: redis:alpine
 
-.use-mysql: &use-mysql
-  services:
-    - mysql:5.7
-    - redis:alpine
-
 .only-schedules-master: &only-schedules-master
   only:
     - schedules@gitlab-org/gitlab-ce
@@ -94,10 +89,6 @@
   <<: *use-pg-10
   image: "dev.gitlab.org:5005/gitlab/gitlab-build-images:ruby-2.6.3-golang-1.11-git-2.21-chrome-73.0-node-12.x-yarn-1.16-postgresql-10-graphicsmagick-1.3.29"
 
-.rspec-metadata-mysql: &rspec-metadata-mysql
-  <<: *rspec-metadata
-  <<: *use-mysql
-
 # DB migration, rollback, and seed jobs
 .db-migrate-reset: &db-migrate-reset
   extends: .dedicated-no-docs-and-no-qa-pull-cache-job
@@ -173,42 +164,6 @@ rspec system pg-10:
   <<: *only-schedules-master
   parallel: 24
 
-rspec unit mysql:
-  <<: *rspec-metadata-mysql
-  <<: *only-schedules-master
-  parallel: 20
-
-rspec integration mysql:
-  <<: *rspec-metadata-mysql
-  <<: *only-schedules-master
-  parallel: 6
-
-rspec system mysql:
-  <<: *rspec-metadata-mysql
-  <<: *only-schedules-master
-  parallel: 24
-
-.rspec-mysql-on-demand: &rspec-mysql-on-demand
-  only:
-    variables:
-      - $CI_COMMIT_MESSAGE =~ /\[run mysql\]/i
-      - $CI_COMMIT_REF_NAME =~ /mysql/
-
-rspec unit mysql on-demand:
-  <<: *rspec-metadata-mysql
-  <<: *rspec-mysql-on-demand
-  parallel: 20
-
-rspec integration mysql on-demand:
-  <<: *rspec-metadata-mysql
-  <<: *rspec-mysql-on-demand
-  parallel: 6
-
-rspec system mysql on-demand:
-  <<: *rspec-metadata-mysql
-  <<: *rspec-mysql-on-demand
-  parallel: 24
-
 rspec-fast-spec-helper:
   <<: *rspec-metadata-pg
   script:
@@ -226,12 +181,6 @@ rspec quarantine pg:
   <<: *rspec-quarantine
   allow_failure: true
 
-rspec quarantine mysql:
-  <<: *rspec-metadata-mysql
-  <<: *rspec-quarantine
-  <<: *only-schedules-master
-  allow_failure: true
-
 static-analysis:
   extends: .dedicated-no-docs-no-db-pull-cache-job
   dependencies:
@@ -281,10 +230,6 @@ db:migrate:reset-pg:
   <<: *db-migrate-reset
   <<: *use-pg
 
-db:migrate:reset-mysql:
-  <<: *db-migrate-reset
-  <<: *use-mysql
-
 db:check-schema-pg:
   <<: *db-migrate-reset
   <<: *use-pg
@@ -295,10 +240,6 @@ migration:path-pg:
   <<: *migration-paths
   <<: *use-pg
 
-migration:path-mysql:
-  <<: *migration-paths
-  <<: *use-mysql
-
 .db-rollback: &db-rollback
   extends: .dedicated-no-docs-and-no-qa-pull-cache-job
   script:
@@ -311,22 +252,12 @@ db:rollback-pg:
   <<: *db-rollback
   <<: *use-pg
 
-db:rollback-mysql:
-  <<: *db-rollback
-  <<: *use-mysql
-
 gitlab:setup-pg:
   <<: *gitlab-setup
   <<: *use-pg
   dependencies:
     - setup-test-env
 
-gitlab:setup-mysql:
-  <<: *gitlab-setup
-  <<: *use-mysql
-  dependencies:
-    - setup-test-env
-
 coverage:
   # Don't include dedicated-no-docs-no-db-pull-cache-job here since we need to
   # download artifacts from all the rspec jobs instead of from setup-test-env only
@@ -357,12 +288,6 @@ coverage:
     - name: redis:alpine
     - name: docker.elastic.co/elasticsearch/elasticsearch:5.6.12
 
-.use-mysql-with-elasticsearch: &use-mysql-with-elasticsearch
-  services:
-    - mysql:5.7.24
-    - redis:alpine
-    - docker.elastic.co/elasticsearch/elasticsearch:5.6.12
-
 .rspec-metadata-ee: &rspec-metadata-ee
   <<: *rspec-metadata
   stage: test
@@ -385,10 +310,6 @@ coverage:
   <<: *rspec-metadata-ee
   <<: *use-pg-with-elasticsearch
 
-.rspec-metadata-mysql-ee: &rspec-metadata-mysql-ee
-  <<: *rspec-metadata-ee
-  <<: *use-mysql-with-elasticsearch
-
 rspec unit pg ee:
   <<: *rspec-metadata-pg-ee
   parallel: 7
@@ -401,36 +322,6 @@ rspec system pg ee:
   <<: *rspec-metadata-pg-ee
   parallel: 5
 
-rspec unit mysql ee:
-  <<: *rspec-metadata-mysql-ee
-  <<: *only-schedules-master
-  parallel: 7
-
-rspec integration mysql ee:
-  <<: *rspec-metadata-mysql-ee
-  <<: *only-schedules-master
-  parallel: 3
-
-rspec system mysql ee:
-  <<: *rspec-metadata-mysql-ee
-  <<: *only-schedules-master
-  parallel: 5
-
-rspec unit mysql ee on-demand:
-  <<: *rspec-metadata-mysql-ee
-  <<: *rspec-mysql-on-demand
-  parallel: 7
-
-rspec integration mysql ee on-demand:
-  <<: *rspec-metadata-mysql-ee
-  <<: *rspec-mysql-on-demand
-  parallel: 3
-
-rspec system mysql ee on-demand:
-  <<: *rspec-metadata-mysql-ee
-  <<: *rspec-mysql-on-demand
-  parallel: 5
-
 .rspec-metadata-pg-geo: &rspec-metadata-pg-geo
   <<: *rspec-metadata
   stage: test
@@ -488,11 +379,6 @@ rspec quarantine pg ee:
   <<: *rspec-quarantine-ee
   <<: *rspec-metadata-pg
 
-rspec quarantine mysql ee:
-  <<: *rspec-quarantine-ee
-  <<: *rspec-metadata-mysql
-  <<: *only-schedules-master
-
 .migration-paths-upgrade-ce-to-ee: &migration-paths-upgrade-ce-to-ee
   extends: .dedicated-no-docs-and-no-qa-pull-cache-job
   variables:
@@ -517,10 +403,6 @@ migration:upgrade-pg-ce-to-ee:
   <<: *migration-paths-upgrade-ce-to-ee
   <<: *use-pg
 
-migration:upgrade-mysql-ce-to-ee:
-  <<: *migration-paths-upgrade-ce-to-ee
-  <<: *use-mysql
-
 db:rollback-pg-geo:
   <<: *db-rollback
   <<: *use-pg

changelogs/unreleased/52442-minimal-remove-mysql-support.yml

+---
+title: Remove MySQL support
+merge_request: 29790
+author:
+type: removed

config/initializers/1_postgresql_only.rb

+# frozen_string_literal: true
+
+raise "PostgreSQL is the only supported database from GitLab 12.1" unless
+  Gitlab::Database.postgresql?

doc/administration/environment_variables.md

@@ -42,7 +42,7 @@ The list of `GITLAB_DATABASE_XXX` variables that you can set is:
 
 Variable | Default value | Overridden by `DATABASE_URL`?
 -------- | ------------- | -----------------------------
-`GITLAB_DATABASE_ADAPTER`   | `postgresql` (for MySQL use `mysql2`) | Yes
+`GITLAB_DATABASE_ADAPTER`   | `postgresql`                          | Yes
 `GITLAB_DATABASE_DATABASE`  | `gitlab_#{ENV['RAILS_ENV']`           | Yes
 `GITLAB_DATABASE_USERNAME`  | `root`                                | Yes
 `GITLAB_DATABASE_PASSWORD`  | None                                  | Yes

doc/administration/geo/replication/database.md

@@ -489,10 +489,6 @@ work:
     gitlab-ctl reconfigure
     ```
 
-## MySQL replication
-
-MySQL replication is not supported for Geo.
-
 ## Troubleshooting
 
 Read the [troubleshooting document](troubleshooting.md).

doc/administration/index.md

@@ -33,7 +33,6 @@ Learn how to install, configure, update, and maintain your GitLab instance.
 
 - [Install](../install/README.md): Requirements, directory structures, and installation methods.
   - [Database load balancing](database_load_balancing.md): Distribute database queries among multiple database servers. **[STARTER ONLY]**
-  - [Omnibus support for external MySQL DB](https://docs.gitlab.com/omnibus/settings/database.html#using-a-mysql-database-management-server-enterprise-edition-only): Omnibus package supports configuring an external MySQL database. **[STARTER ONLY]**
   - [Omnibus support for log forwarding](https://docs.gitlab.com/omnibus/settings/logs.html#udp-log-shipping-gitlab-enterprise-edition-only) **[STARTER ONLY]**
 - [High Availability](high_availability/README.md): Configure multiple servers for scaling or high availability.
   - [Installing GitLab HA on Amazon Web Services (AWS)](../install/aws/index.md): Set up GitLab High Availability on Amazon AWS.

doc/development/architecture.md

@@ -695,7 +695,7 @@ We've also detailed [our architecture of GitLab.com](https://about.gitlab.com/ha
 [runner-gdk]: https://gitlab.com/gitlab-org/gitlab-development-kit/blob/master/doc/howto/runner.md
 [database-migrations-omnibus]: https://docs.gitlab.com/omnibus/settings/database.html#disabling-automatic-database-migration
 [database-migrations-charts]: https://docs.gitlab.com/charts/charts/gitlab/migrations/
-[database-migrations-source]: ../update/upgrading_from_source.md#14-install-libs-migrations-etc
+[database-migrations-source]: ../update/upgrading_from_source.md#13-install-libs-migrations-etc
 [certificate-management-omnibus]: https://docs.gitlab.com/omnibus/settings/ssl.html
 [certificate-management-charts]: https://docs.gitlab.com/charts/installation/tls.html
 [certificate-management-source]: ../install/installation.md#using-https

doc/development/rake_tasks.md

@@ -80,30 +80,6 @@ There are a few environment flags you can pass to change how projects are seeded
 - `LARGE_PROJECTS`: defaults to false. If set will clone 6 large projects to help with testing.
 - `FORK`: defaults to false. If set to `true` will fork `torvalds/linux` five times. Can also be set to an existing project full_path and it will fork that instead.
 
-### Notes for MySQL
-
-Since the seeds would contain various UTF-8 characters, such as emojis or so,
-we'll need to make sure that we're using `utf8mb4` for all the encoding
-settings and `utf8mb4_unicode_ci` for collation. Please check
-[MySQL utf8mb4 support](../install/database_mysql.md#mysql-utf8mb4-support)
-
-Make sure that `config/database.yml` has `encoding: utf8mb4`, too.
-
-Next, we'll need to update the schema to make the indices fit:
-
-``` shell
-sed -i 's/limit: 255/limit: 191/g' db/schema.rb
-```
-
-Then run the setup script:
-
-``` shell
-bundle exec rake setup
-```
-
-To make sure that indices still fit. You could find great details in:
-[How to support full Unicode in MySQL databases](https://mathiasbynens.be/notes/mysql-utf8mb4)
-
 ## Run tests
 
 In order to run the test you can use the following commands:

doc/development/swapping_tables.md

@@ -39,14 +39,6 @@ PostgreSQL you can use the `reset_pk_sequence!` method like so:
 reset_pk_sequence!('events')
 ```
 
-For MySQL however you need to do run the following:
-
-```ruby
-amount = Event.pluck('COALESCE(MAX(id), 1)').first
-
-execute "ALTER TABLE events AUTO_INCREMENT = #{amount}"
-```
-
 Failure to reset the primary keys will result in newly created rows starting
 with an ID value of 1. Depending on the existing data this can then lead to
 duplicate key constraints from popping up, preventing users from creating new

doc/install/installation.md

@@ -293,10 +293,9 @@ sudo adduser --disabled-login --gecos 'GitLab' git
 
 ## 6. Database
 
-We recommend using a PostgreSQL database. For MySQL, see the [MySQL setup guide](database_mysql.md).
-
 NOTE: **Note:**
-Because we need to make use of extensions and concurrent index removal, you need at least PostgreSQL 9.2.
+Starting from GitLab 12.1, only PostgreSQL is supported. Because we need to make
+use of extensions and concurrent index removal, you need at least PostgreSQL 9.2.
 
 1. Install the database packages:
 
@@ -502,13 +501,8 @@ If you want to use HTTPS, see [Using HTTPS](#using-https) for the additional ste
 ### Configure GitLab DB Settings
 
 ```sh
-# PostgreSQL only:
 sudo -u git cp config/database.yml.postgresql config/database.yml
 
-# MySQL only:
-sudo -u git cp config/database.yml.mysql config/database.yml
-
-# PostgreSQL only:
 # Remove host, username, and password lines from config/database.yml.
 # Once modified, the `production` settings will be as follows:
 #
@@ -520,7 +514,7 @@ sudo -u git cp config/database.yml.mysql config/database.yml
 #
 sudo -u git -H editor config/database.yml
 
-# MySQL and remote PostgreSQL only:
+# Remote PostgreSQL only:
 # Update username/password in config/database.yml.
 # You only need to adapt the production settings (first part).
 # If you followed the database guide then please do as follows:
@@ -528,7 +522,6 @@ sudo -u git -H editor config/database.yml
 # You can keep the double quotes around the password
 sudo -u git -H editor config/database.yml
 
-# PostgreSQL and MySQL:
 # Make config/database.yml readable to git only
 sudo -u git -H chmod o-rwx config/database.yml
 ```
@@ -544,11 +537,7 @@ Make sure you have `bundle` (run `bundle -v`):
 - `< 2.x`.
 
 ```sh
-# For PostgreSQL (note, the option says "without ... mysql")
 sudo -u git -H bundle install --deployment --without development test mysql aws kerberos
-
-# Or if you use MySQL (note, the option says "without ... postgres")
-sudo -u git -H bundle install --deployment --without development test postgres aws kerberos
 ```
 
 NOTE: **Note:**

doc/install/requirements.md

@@ -104,32 +104,10 @@ installation (e.g. the number of users, projects, etc).
 
 We currently support the following databases:
 
-- PostgreSQL (highly recommended)
-- MySQL/MariaDB (strongly discouraged, not all GitLab features are supported, no support for [MySQL/MariaDB GTID](https://mariadb.com/kb/en/mariadb/gtid/))
-
-We highly recommend the use of PostgreSQL instead of MySQL/MariaDB as not all
-features of GitLab work with MySQL/MariaDB:
-
-1. MySQL support for subgroups was [dropped with GitLab 9.3][post].
-   See [issue #30472][30472] for more information.
-1. Geo does [not support MySQL](../administration/geo/replication/database.md). This means no supported Disaster Recovery solution if using MySQL. **[PREMIUM ONLY]**
-1. [Zero downtime migrations](../update/README.md#upgrading-without-downtime) do not work with MySQL.
-1. [Database load balancing](../administration/database_load_balancing.md) is
-   supported only for PostgreSQL. **[PREMIUM ONLY]**
-1. GitLab [optimizes the loading of dashboard events](https://gitlab.com/gitlab-org/gitlab-ce/issues/31806) using [PostgreSQL LATERAL JOINs](https://blog.heapanalytics.com/postgresqls-powerful-new-join-type-lateral/).
-1. In general, SQL optimized for PostgreSQL may run much slower in MySQL due to
-   differences in query planners. For example, subqueries that work well in PostgreSQL
-   may not be [performant in MySQL](https://dev.mysql.com/doc/refman/5.7/en/optimizing-subqueries.html).
-1. Binary column index length is limited to 20 bytes. This is accomplished with [a hack](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/config/initializers/mysql_set_length_for_binary_indexes.rb).
-1. MySQL requires a variety of hacks to increase limits on various columns, [for example](https://gitlab.com/gitlab-org/gitlab-ce/issues/49583).
-1. [The milestone filter runs slower queries on MySQL](https://gitlab.com/gitlab-org/gitlab-ce/issues/51173#note_99391731).
-1. We expect this list to grow over time.
-
-Existing users using GitLab with MySQL/MariaDB are advised to
-[migrate to PostgreSQL](../update/mysql_to_postgresql.md) instead.
-
-[30472]: https://gitlab.com/gitlab-org/gitlab-ce/issues/30472
-[post]: https://about.gitlab.com/2017/06/22/gitlab-9-3-released/#dropping-support-for-subgroups-in-mysql
+- PostgreSQL
+
+Support for MySQL was removed in GitLab 12.1. Existing users using GitLab with
+MySQL/MariaDB are advised to [migrate to PostgreSQL](../update/mysql_to_postgresql.md) before upgrading.
 
 ### PostgreSQL Requirements
 

doc/integration/omniauth.md

@@ -194,11 +194,7 @@ from the Omniauth provider's documentation.
 
         gem "omniauth-your-auth-provider"
 
--   If you're using MySQL, install the new Omniauth provider gem by running the following command:
-
-        sudo -u git -H bundle install --without development test postgres --path vendor/bundle --no-deployment
-
--   If you're using PostgreSQL, install the new Omniauth provider gem by running the following command:
+-   Install the new Omniauth provider gem by running the following command:
 
         sudo -u git -H bundle install --without development test mysql --path vendor/bundle --no-deployment
 

doc/university/README.md

@@ -149,7 +149,6 @@ The GitLab University curriculum is composed of GitLab videos, screencasts, pres
 1. [How to Install GitLab with Omnibus - Video](https://www.youtube.com/watch?v=Q69YaOjqNhg)
 1. [Installing GitLab - Online Course](https://courses.platzi.com/classes/git-gitlab/concepto/part-1/part-3/material/)
 1. [Using a Non-Packaged PostgreSQL Database](https://gitlab.com/gitlab-org/omnibus-gitlab/blob/master/README.md#using-a-non-packaged-postgresql-database-management-server)
-1. [Using a MySQL Database](https://gitlab.com/gitlab-org/omnibus-gitlab/blob/master/README.md#using-a-mysql-database-management-server-enterprise-edition-only)
 1. [Installing GitLab on Microsoft Azure](https://about.gitlab.com/2016/07/13/how-to-setup-a-gitlab-instance-on-microsoft-azure/)
 1. [Installing GitLab on Digital Ocean](https://about.gitlab.com/2016/04/27/getting-started-with-gitlab-and-digitalocean/)
 

doc/update/README.md

@@ -49,8 +49,7 @@ However, for this to work there are the following requirements:
 - You have to use [post-deployment
    migrations](../development/post_deployment_migrations.md) (included in
    zero downtime update steps below).
-- You are using PostgreSQL. If you are using MySQL please look at the release
-   post to see if downtime is required.
+- You are using PostgreSQL. Starting from GitLab 12.1, MySQL is not supported.
 
 Most of the time you can safely upgrade from a patch release to the next minor
 release if the patch release is not the latest. For example, upgrading from
@@ -140,8 +139,6 @@ possible.
 
 - [MySQL to PostgreSQL](mysql_to_postgresql.md) guides you through migrating
   your database from MySQL to PostgreSQL.
-- [MySQL installation guide](../install/database_mysql.md) contains additional
-  information about configuring GitLab to work with a MySQL database.
 - [Restoring from backup after a failed upgrade](restore_after_failure.md)
 - [Upgrading PostgreSQL Using Slony](upgrading_postgresql_using_slony.md), for
   upgrading a PostgreSQL database with minimal downtime.

doc/update/mysql_to_postgresql.md

 ---
-last_updated: 2019-03-27
+last_updated: 2019-06-18
 ---
 
 # Migrating from MySQL to PostgreSQL
@@ -9,6 +9,10 @@ migrate it to a PostgreSQL database.
 
 ## Requirements
 
+NOTE: **Note:**
+Support for MySQL was removed in GitLab 12.1. This procedure should be performed
+**before** installing GitLab 12.1.
+
 [pgloader](http://pgloader.io) 3.4.1+ is required.
 
 You can install it directly from your distribution, for example in

doc/update/patch_versions.md

@@ -13,8 +13,6 @@ You can select the tag in the version dropdown in the top left corner of GitLab
 ### 0. Backup
 
 It's useful to make a backup just in case things go south:
-(With MySQL, this may require granting "LOCK TABLES" privileges to the GitLab
-user on the database version)
 
 ```bash
 cd /home/git/gitlab
@@ -48,12 +46,8 @@ sudo -u git -H git checkout LATEST_TAG -b LATEST_TAG
 ```bash
 cd /home/git/gitlab
 
-# PostgreSQL
 sudo -u git -H bundle install --without development test mysql --deployment
 
-# MySQL
-sudo -u git -H bundle install --without development test postgres --deployment
-
 # Optional: clean up old gems
 sudo -u git -H bundle clean
 

doc/update/upgrading_from_source.md

@@ -239,29 +239,7 @@ sudo -u git -H git checkout v$(</home/git/gitlab/GITLAB_PAGES_VERSION)
 sudo -u git -H make
 ```
 
-### 12. Update MySQL permissions
-
-If you are using MySQL you need to grant the GitLab user the necessary
-permissions on the database:
-
-```bash
-mysql -u root -p -e "GRANT TRIGGER ON \`gitlabhq_production\`.* TO 'git'@'localhost';"
-```
-
-If you use MySQL with replication, or just have MySQL configured with binary logging,
-you will need to also run the following on all of your MySQL servers:
-
-```bash
-mysql -u root -p -e "SET GLOBAL log_bin_trust_function_creators = 1;"
-```
-
-You can make this setting permanent by adding it to your `my.cnf`:
-
-```
-log_bin_trust_function_creators=1
-```
-
-### 13. Update configuration files
+### 12. Update configuration files
 
 #### New configuration options for `gitlab.yml`
 
@@ -335,18 +313,13 @@ For Ubuntu 16.04.1 LTS:
 sudo systemctl daemon-reload
 ```
 
-### 14. Install libs, migrations, etc.
+### 13. Install libs, migrations, etc.
 
 ```bash
 cd /home/git/gitlab
 
-# PostgreSQL installations (note: the line below states '--without mysql')
 sudo -u git -H bundle install --deployment --without development test mysql aws kerberos
 
-# MySQL installations (note: the line below states '--without postgres')
-sudo -u git -H bundle install --deployment --without development test postgres aws kerberos
-
-
 # Optional: clean up old gems
 sudo -u git -H bundle clean
 
@@ -364,17 +337,14 @@ sudo -u git -H bundle exec rake yarn:install gitlab:assets:clean gitlab:assets:c
 sudo -u git -H bundle exec rake cache:clear RAILS_ENV=production
 ```
 
-**MySQL installations**: Run through the `MySQL strings limits` and `Tables and
-data conversion to utf8mb4` [tasks](../install/database_mysql.md).
-
-### 15. Start application
+### 14. Start application
 
 ```bash
 sudo service gitlab start
 sudo service nginx restart
 ```
 
-### 16. Check application status
+### 15. Check application status
 
 Check if GitLab and its environment are configured correctly:
 

doc/user/group/subgroups/index.md

@@ -5,8 +5,7 @@ type: reference, howto, concepts
 # Subgroups
 
 NOTE: **Note:**
-[Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/2772) in GitLab 9.0. Not available when using MySQL as external
-database (support removed in GitLab 9.3 [due to performance reasons](https://gitlab.com/gitlab-org/gitlab-ce/issues/30472#note_27747600)).
+[Introduced](https://gitlab.com/gitlab-org/gitlab-ce/issues/2772) in GitLab 9.0.
 
 Subgroups, also known as nested groups or hierarchical groups, allow you to have up to 20
 levels of groups.
@@ -21,16 +20,6 @@ By using subgroups you can do the following:
 - **Make it easier to manage people and control visibility.** Give people
   different [permissions](../../permissions.md#group-members-permissions) depending on their group [membership](#membership).
 
-## Database Requirements
-
-Subgroups are only supported when you use PostgreSQL. Supporting subgroups on MySQL in an
-efficient way is not possible due to MySQL's limitations.
-
-See the following links for more information:
-
-- <https://gitlab.com/gitlab-org/gitlab-ce/issues/30472>
-- <https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10885>
-
 ## Overview
 
 A group can have many subgroups inside it, and at the same time a group can have