Only support postgresql

MySQL support has been removed

.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?