Remove redundant and dead code related to MySQL

In https://gitlab.com/gitlab-org/gitlab-foss/merge_requests/29790 we
removed support for MySQL.

Follow up https://gitlab.com/gitlab-org/gitlab/commit/4aa76dddecc048cef24963323afe59f1c120cb72

db/migrate/20180113220114_rework_redirect_routes_indexes.rb

@@ -25,10 +25,6 @@ class ReworkRedirectRoutesIndexes < ActiveRecord::Migration[4.2]
         remove_concurrent_index(:redirect_routes, :permanent)
       end
 
-      # If we're on MySQL then the existing index on path is ok. But on
-      # Postgres we need to clean things up:
-      break unless Gitlab::Database.postgresql?
-
       if_not_exists = Gitlab::Database.version.to_f >= 9.5 ? "IF NOT EXISTS" : ""
 
       # Unique index on lower(path) across both types of redirect_routes:
@@ -53,8 +49,6 @@ class ReworkRedirectRoutesIndexes < ActiveRecord::Migration[4.2]
     disable_statement_timeout do
       add_concurrent_index(:redirect_routes, :permanent)
 
-      break unless Gitlab::Database.postgresql?
-
       execute("CREATE INDEX CONCURRENTLY #{OLD_INDEX_NAME_PATH_TPOPS} ON redirect_routes (path varchar_pattern_ops);")
       execute("CREATE INDEX CONCURRENTLY #{OLD_INDEX_NAME_PATH_LOWER} ON redirect_routes (LOWER(path));")
 

db/migrate/20180308052825_add_section_name_id_index_on_ci_build_trace_sections.rb

@@ -8,16 +8,10 @@ class AddSectionNameIdIndexOnCiBuildTraceSections < ActiveRecord::Migration[4.2]
   disable_ddl_transaction!
 
   def up
-    # MySQL may already have this as a foreign key
-    unless index_exists?(:ci_build_trace_sections, :section_name_id, name: INDEX_NAME)
-      add_concurrent_index :ci_build_trace_sections, :section_name_id, name: INDEX_NAME
-    end
+    add_concurrent_index :ci_build_trace_sections, :section_name_id, name: INDEX_NAME
   end
 
   def down
-    # We cannot remove index for MySQL because it's needed for foreign key
-    if Gitlab::Database.postgresql?
-      remove_concurrent_index :ci_build_trace_sections, :section_name_id, name: INDEX_NAME
-    end
+    remove_concurrent_index :ci_build_trace_sections, :section_name_id, name: INDEX_NAME
   end
 end

db/migrate/20180320182229_add_indexes_for_user_activity_queries.rb

@@ -13,28 +13,6 @@ class AddIndexesForUserActivityQueries < ActiveRecord::Migration[4.2]
   def down
     remove_concurrent_index :events, [:author_id, :project_id] if index_exists?(:events, [:author_id, :project_id])
 
-    patch_foreign_keys do
-      remove_concurrent_index :user_interacted_projects, :user_id if index_exists?(:user_interacted_projects, :user_id)
-    end
-  end
-
-  private
-
-  def patch_foreign_keys
-    return yield if Gitlab::Database.postgresql?
-
-    # MySQL doesn't like to remove the index with a foreign key using it.
-    remove_foreign_key :user_interacted_projects, :users if fk_exists?(:user_interacted_projects, :user_id)
-
-    yield
-
-    # Let's re-add the foreign key using the existing index on (user_id, project_id)
-    add_concurrent_foreign_key :user_interacted_projects, :users, column: :user_id unless fk_exists?(:user_interacted_projects, :user_id)
-  end
-
-  def fk_exists?(table, column)
-    foreign_keys(table).any? do |key|
-      key.options[:column] == column.to_s
-    end
+    remove_concurrent_index :user_interacted_projects, :user_id if index_exists?(:user_interacted_projects, :user_id)
   end
 end

db/migrate/20180711103851_drop_duplicate_protected_tags.rb

@@ -29,14 +29,7 @@ class DropDuplicateProtectedTags < ActiveRecord::Migration[4.2]
         .where(project_id: projects)
         .where.not(id: ids)
 
-      if Gitlab::Database.postgresql?
-        tags.delete_all
-      else
-        # Workaround needed for MySQL
-        sql = "SELECT id FROM (#{tags.to_sql}) protected_tags"
-
-        ProtectedTag.where("id IN (#{sql})").delete_all # rubocop:disable GitlabSecurity/SqlInjection
-      end
+      tags.delete_all
     end
   end
 

db/migrate/20180927073410_add_index_to_project_deploy_tokens_deploy_token_id.rb

@@ -8,11 +8,10 @@ class AddIndexToProjectDeployTokensDeployTokenId < ActiveRecord::Migration[4.2]
   disable_ddl_transaction!
 
   def up
-    # MySQL already has index inserted
-    add_concurrent_index :project_deploy_tokens, :deploy_token_id if Gitlab::Database.postgresql?
+    add_concurrent_index :project_deploy_tokens, :deploy_token_id
   end
 
   def down
-    remove_concurrent_index(:project_deploy_tokens, :deploy_token_id) if Gitlab::Database.postgresql?
+    remove_concurrent_index(:project_deploy_tokens, :deploy_token_id)
   end
 end

db/post_migrate/20180119121225_remove_redundant_pipeline_stages.rb

@@ -50,17 +50,9 @@ class RemoveRedundantPipelineStages < ActiveRecord::Migration[4.2]
         UPDATE ci_builds SET stage_id = NULL WHERE stage_id IN (#{redundant_stages_ids})
       SQL
 
-      if Gitlab::Database.postgresql?
-        execute <<~SQL
-          DELETE FROM ci_stages WHERE id IN (#{redundant_stages_ids})
-        SQL
-      else # We can't modify a table we are selecting from on MySQL
-        execute <<~SQL
-          DELETE a FROM ci_stages AS a, ci_stages AS b
-            WHERE a.pipeline_id = b.pipeline_id AND a.name = b.name
-              AND a.id <> b.id
-        SQL
-      end
+      execute <<~SQL
+        DELETE FROM ci_stages WHERE id IN (#{redundant_stages_ids})
+      SQL
     end
   end
 end

db/post_migrate/20180223124427_build_user_interacted_projects_table.rb

@@ -12,11 +12,7 @@ class BuildUserInteractedProjectsTable < ActiveRecord::Migration[4.2]
   disable_ddl_transaction!
 
   def up
-    if Gitlab::Database.postgresql?
-      PostgresStrategy.new
-    else
-      MysqlStrategy.new
-    end.up
+    PostgresStrategy.new.up
 
     if index_exists_by_name?(:user_interacted_projects, CreateUserInteractedProjectsTable::INDEX_NAME)
       remove_concurrent_index_by_name :user_interacted_projects, CreateUserInteractedProjectsTable::INDEX_NAME
@@ -140,30 +136,4 @@ class BuildUserInteractedProjectsTable < ActiveRecord::Migration[4.2]
       remove_concurrent_index(*args) if index_exists?(*args)
     end
   end
-
-  class MysqlStrategy < ActiveRecord::Migration[4.2]
-    include Gitlab::Database::MigrationHelpers
-
-    def up
-      execute <<~SQL
-        INSERT INTO user_interacted_projects (user_id, project_id)
-        SELECT e.user_id, e.project_id
-        FROM (SELECT DISTINCT author_id AS user_id, project_id FROM events WHERE project_id IS NOT NULL) AS e
-        LEFT JOIN user_interacted_projects ucp USING (user_id, project_id)
-        WHERE ucp.user_id IS NULL
-      SQL
-
-      unless index_exists?(:user_interacted_projects, [:project_id, :user_id])
-        add_concurrent_index :user_interacted_projects, [:project_id, :user_id], unique: true, name: UNIQUE_INDEX_NAME
-      end
-
-      unless foreign_key_exists?(:user_interacted_projects, :users, column: :user_id)
-        add_concurrent_foreign_key :user_interacted_projects, :users, column: :user_id, on_delete: :cascade
-      end
-
-      unless foreign_key_exists?(:user_interacted_projects, :projects, column: :project_id)
-        add_concurrent_foreign_key :user_interacted_projects, :projects, column: :project_id, on_delete: :cascade
-      end
-    end
-  end
 end

scripts/prepare_build.sh

@@ -16,13 +16,7 @@ retry gem install knapsack --no-document
 cp config/gitlab.yml.example config/gitlab.yml
 sed -i 's/bin_path: \/usr\/bin\/git/bin_path: \/usr\/local\/bin\/git/' config/gitlab.yml
 
-# Determine the database by looking at the job name.
-# This would make the default database postgresql.
-if [[ "${CI_JOB_NAME#*mysql}" != "$CI_JOB_NAME" ]]; then
-  export GITLAB_DATABASE='mysql'
-else
-  export GITLAB_DATABASE='postgresql'
-fi
+export GITLAB_DATABASE='postgresql'
 
 cp config/database.yml.$GITLAB_DATABASE config/database.yml
 
@@ -41,12 +35,6 @@ if [ "$GITLAB_DATABASE" = 'postgresql' ]; then
     sed -i 's/localhost/postgres/g' config/database_geo.yml
     sed -i 's/username: git/username: postgres/g' config/database_geo.yml
   fi
-else # Assume it's mysql
-  sed -i 's/localhost/mysql/g' config/database.yml
-
-  if [ -f config/database_geo.yml ]; then
-    sed -i 's/localhost/mysql/g' config/database_geo.yml
-  fi
 fi
 
 cp config/resque.yml.example config/resque.yml
@@ -63,6 +51,6 @@ sed -i 's|url:.*$|url: redis://redis:6379/12|g' config/redis.shared_state.yml
 
 if [ "$SETUP_DB" != "false" ]; then
   setup_db
-elif getent hosts postgres || getent hosts mysql; then
+elif getent hosts postgres; then
   setup_db_user_only
 fi

scripts/utils.sh

@@ -16,8 +16,6 @@ function retry() {
 function setup_db_user_only() {
     if [ "$GITLAB_DATABASE" = "postgresql" ]; then
         source scripts/create_postgres_user.sh
-    else
-        source scripts/create_mysql_user.sh
     fi
 }
 
@@ -26,10 +24,6 @@ function setup_db() {
 
     bundle exec rake db:drop db:create db:schema:load db:migrate
 
-    if [ "$GITLAB_DATABASE" = "mysql" ]; then
-        bundle exec rake add_limits_mysql
-    fi
-
     bundle exec rake gitlab:db:setup_ee
 }