Further remove code branches by database type

We dropped MySQL support and a lot of mysql specific code has been
removed in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/29608.

This comes in from the other direction and removes any `if postgresql?`
branches.

app/finders/issuable_finder.rb

@@ -320,7 +320,6 @@ class IssuableFinder
   def use_cte_for_search?
     strong_memoize(:use_cte_for_search) do
       next false unless search
-      next false unless Gitlab::Database.postgresql?
       # Only simple unsorted & simple sorts can use CTE
       next false if params[:sort].present? && !params[:sort].in?(klass.simple_sorts.keys)

app/finders/members_finder.rb

@@ -59,35 +59,16 @@ class MembersFinder
   def distinct_on(union)
     # We're interested in a list of members without duplicates by user_id.
     # We prefer project members over group members, project members should go first.
-    if Gitlab::Database.postgresql?
-      <<~SQL
-          SELECT DISTINCT ON (user_id, invite_email) member_union.*
-          FROM (#{union.to_sql}) AS member_union
-          ORDER BY user_id,
-            invite_email,
-            CASE
-              WHEN type = 'ProjectMember' THEN 1
-              WHEN type = 'GroupMember' THEN 2
-              ELSE 3
-            END
-      SQL
-    else
-      # Older versions of MySQL do not support window functions (and DISTINCT ON is postgres-specific).
-      <<~SQL
-          SELECT t1.*
-          FROM (#{union.to_sql}) AS t1
-          JOIN (
-            SELECT
-              COALESCE(user_id, -1) AS user_id,
-              COALESCE(invite_email, 'NULL') AS invite_email,
-              MIN(CASE WHEN type = 'ProjectMember' THEN 1 WHEN type = 'GroupMember' THEN 2 ELSE 3 END) AS type_number
-            FROM
-            (#{union.to_sql}) AS t3
-            GROUP BY COALESCE(user_id, -1), COALESCE(invite_email, 'NULL')
-          ) AS t2 ON COALESCE(t1.user_id, -1) = t2.user_id
-                 AND COALESCE(t1.invite_email, 'NULL') = t2.invite_email
-                 AND CASE WHEN t1.type = 'ProjectMember' THEN 1 WHEN t1.type = 'GroupMember' THEN 2 ELSE 3 END = t2.type_number
-      SQL
-    end
+    <<~SQL
+        SELECT DISTINCT ON (user_id, invite_email) member_union.*
+        FROM (#{union.to_sql}) AS member_union
+        ORDER BY user_id,
+          invite_email,
+          CASE
+            WHEN type = 'ProjectMember' THEN 1
+            WHEN type = 'GroupMember' THEN 2
+            ELSE 3
+          END
+    SQL
   end
 end

app/models/merge_request.rb

@@ -1249,15 +1249,8 @@ class MergeRequest < ApplicationRecord
   end
   def all_commits
-    # MySQL doesn't support LIMIT in a subquery.
-    diffs_relation = if Gitlab::Database.postgresql?
-                       merge_request_diffs.recent
-                     else
-                       merge_request_diffs
-                     end
-
     MergeRequestDiffCommit
-      .where(merge_request_diff: diffs_relation)
+      .where(merge_request_diff: merge_request_diffs.recent)
       .limit(10_000)
   end

app/models/milestone.rb

@@ -149,29 +149,10 @@ class Milestone < ApplicationRecord
   end
   def self.upcoming_ids(projects, groups)
-    rel = unscoped
-            .for_projects_and_groups(projects, groups)
-            .active.where('milestones.due_date > CURRENT_DATE')
-
-    if Gitlab::Database.postgresql?
-      rel.order(:project_id, :group_id, :due_date).select('DISTINCT ON (project_id, group_id) id')
-    else
-      # We need to use MySQL's NULL-safe comparison operator `<=>` here
-      # because one of `project_id` or `group_id` is always NULL
-      join_clause = <<~HEREDOC
-        LEFT OUTER JOIN milestones earlier_milestones
-          ON milestones.project_id <=> earlier_milestones.project_id
-            AND milestones.group_id <=> earlier_milestones.group_id
-            AND milestones.due_date > earlier_milestones.due_date
-            AND earlier_milestones.due_date > CURRENT_DATE
-            AND earlier_milestones.state = 'active'
-      HEREDOC
-
-      rel
-        .joins(join_clause)
-        .where('earlier_milestones.id IS NULL')
-        .select(:id)
-    end
+    unscoped
+      .for_projects_and_groups(projects, groups)
+      .active.where('milestones.due_date > CURRENT_DATE')
+      .order(:project_id, :group_id, :due_date).select('DISTINCT ON (project_id, group_id) id')
   end
   def participants

app/models/redirect_route.rb

@@ -11,11 +11,7 @@ class RedirectRoute < ApplicationRecord
     uniqueness: { case_sensitive: false }
   scope :matching_path_and_descendants, -> (path) do
-    wheres = if Gitlab::Database.postgresql?
-               'LOWER(redirect_routes.path) = LOWER(?) OR LOWER(redirect_routes.path) LIKE LOWER(?)'
-             else
-               'redirect_routes.path = ? OR redirect_routes.path LIKE ?'
-             end
+    wheres = 'LOWER(redirect_routes.path) = LOWER(?) OR LOWER(redirect_routes.path) LIKE LOWER(?)'
     where(wheres, path, "#{sanitize_sql_like(path)}/%")
   end

app/services/cohorts_service.rb

@@ -95,10 +95,6 @@ class CohortsService
   # rubocop: enable CodeReuse/ActiveRecord
   def column_to_date(column)
-    if Gitlab::Database.postgresql?
-      "CAST(DATE_TRUNC('month', #{column}) AS date)"
-    else
-      "STR_TO_DATE(DATE_FORMAT(#{column}, '%Y-%m-01'), '%Y-%m-%d')"
-    end
+    "CAST(DATE_TRUNC('month', #{column}) AS date)"
   end
 end

app/services/projects/base_move_relations_service.rb

@@ -13,14 +13,9 @@ module Projects
     private
-    # rubocop: disable CodeReuse/ActiveRecord
     def prepare_relation(relation, id_param = :id)
-      if Gitlab::Database.postgresql?
-        relation
-      else
-        relation.model.where("#{id_param}": relation.pluck(id_param))
-      end
+      # TODO: Refactor and remove this method (https://gitlab.com/gitlab-org/gitlab-ce/issues/65054)
+      relation
     end
-    # rubocop: enable CodeReuse/ActiveRecord
   end
 end

app/services/projects/fetch_statistics_increment_service.rb

@@ -12,14 +12,9 @@ module Projects
       increment_fetch_count_sql = <<~SQL
         INSERT INTO #{table_name} (project_id, date, fetch_count)
         VALUES (#{project.id}, '#{Date.today}', 1)
+        ON CONFLICT (project_id, date) DO UPDATE SET fetch_count = #{table_name}.fetch_count + 1
       SQL
-      increment_fetch_count_sql += if Gitlab::Database.postgresql?
-                                     "ON CONFLICT (project_id, date) DO UPDATE SET fetch_count = #{table_name}.fetch_count + 1"
-                                   else
-                                     "ON DUPLICATE KEY UPDATE fetch_count = #{table_name}.fetch_count + 1"
-                                   end
-
       ActiveRecord::Base.connection.execute(increment_fetch_count_sql)
     end

app/workers/background_migration_worker.rb

@@ -76,8 +76,6 @@ class BackgroundMigrationWorker
   # class_name - The name of the background migration that we might want to
   #              run.
   def healthy_database?
-    return true unless Gitlab::Database.postgresql?
-
     !Postgresql::ReplicationSlot.lag_too_great?
   end

lib/gitlab/background_migration/migrate_stage_index.rb

@@ -13,34 +13,22 @@ module Gitlab
       private
       def migrate_stage_index_sql(start_id, stop_id)
-        if Gitlab::Database.postgresql?
-          <<~SQL
-            WITH freqs AS (
-              SELECT stage_id, stage_idx, COUNT(*) AS freq FROM ci_builds
-                WHERE stage_id BETWEEN #{start_id} AND #{stop_id}
-                  AND stage_idx IS NOT NULL
-                GROUP BY stage_id, stage_idx
-            ), indexes AS (
-              SELECT DISTINCT stage_id, first_value(stage_idx)
-                OVER (PARTITION BY stage_id ORDER BY freq DESC) AS index
-                FROM freqs
-            )
-            UPDATE ci_stages SET position = indexes.index
-              FROM indexes WHERE indexes.stage_id = ci_stages.id
-                AND ci_stages.position IS NULL;
-          SQL
-        else
-          <<~SQL
-            UPDATE ci_stages
-              SET position =
-                (SELECT stage_idx FROM ci_builds
-                  WHERE ci_builds.stage_id = ci_stages.id
-                  GROUP BY ci_builds.stage_idx ORDER BY COUNT(*) DESC LIMIT 1)
-            WHERE ci_stages.id BETWEEN #{start_id} AND #{stop_id}
-              AND ci_stages.position IS NULL
-          SQL
-        end
+        <<~SQL
+          WITH freqs AS (
+            SELECT stage_id, stage_idx, COUNT(*) AS freq FROM ci_builds
+              WHERE stage_id BETWEEN #{start_id} AND #{stop_id}
+                AND stage_idx IS NOT NULL
+              GROUP BY stage_id, stage_idx
+          ), indexes AS (
+            SELECT DISTINCT stage_id, first_value(stage_idx)
+              OVER (PARTITION BY stage_id ORDER BY freq DESC) AS index
+              FROM freqs
+          )
+          UPDATE ci_stages SET position = indexes.index
+            FROM indexes WHERE indexes.stage_id = ci_stages.id
+              AND ci_stages.position IS NULL;
+        SQL
       end
     end
   end

lib/gitlab/background_migration/prepare_untracked_uploads.rb

@@ -147,19 +147,13 @@ module Gitlab
         "#{UntrackedFile.table_name} (path) VALUES #{values}"
       end
-      def postgresql?
-        strong_memoize(:postgresql) do
-          Gitlab::Database.postgresql?
-        end
-      end
-
       def can_bulk_insert_and_ignore_duplicates?
         !postgresql_pre_9_5?
       end
       def postgresql_pre_9_5?
         strong_memoize(:postgresql_pre_9_5) do
-          postgresql? && Gitlab::Database.version.to_f < 9.5
+          Gitlab::Database.version.to_f < 9.5
         end
       end

lib/gitlab/background_migration/remove_restricted_todos.rb

@@ -50,14 +50,7 @@ module Gitlab
       private
       def remove_non_members_todos(project_id)
-        if Gitlab::Database.postgresql?
-          batch_remove_todos_cte(project_id)
-        else
-          unauthorized_project_todos(project_id)
-            .each_batch(of: 5000) do |batch|
-              batch.delete_all
-            end
-        end
+        batch_remove_todos_cte(project_id)
       end
       def remove_confidential_issue_todos(project_id)
@@ -90,13 +83,7 @@ module Gitlab
           next if target_types.empty?
-          if Gitlab::Database.postgresql?
-            batch_remove_todos_cte(project_id, target_types)
-          else
-            unauthorized_project_todos(project_id)
-              .where(target_type: target_types)
-              .delete_all
-          end
+          batch_remove_todos_cte(project_id, target_types)
         end
       end

lib/gitlab/ci/charts.rb

@@ -21,16 +21,10 @@ module Gitlab
       module MonthlyInterval
         # rubocop: disable CodeReuse/ActiveRecord
         def grouped_count(query)
-          if Gitlab::Database.postgresql?
-            query
-              .group("to_char(#{::Ci::Pipeline.table_name}.created_at, '01 Month YYYY')")
-              .count(:created_at)
-              .transform_keys(&:squish)
-          else
-            query
-              .group("DATE_FORMAT(#{::Ci::Pipeline.table_name}.created_at, '01 %M %Y')")
-              .count(:created_at)
-          end
+          query
+            .group("to_char(#{::Ci::Pipeline.table_name}.created_at, '01 Month YYYY')")
+            .count(:created_at)
+            .transform_keys(&:squish)
         end
         # rubocop: enable CodeReuse/ActiveRecord

lib/gitlab/contributions_calendar.rb

@@ -84,11 +84,7 @@ module Gitlab
         .and(t[:created_at].lteq(Date.current.end_of_day))
         .and(t[:author_id].eq(contributor.id))
-      date_interval = if Gitlab::Database.postgresql?
-                        "INTERVAL '#{Time.zone.now.utc_offset} seconds'"
-                      else
-                        "INTERVAL #{Time.zone.now.utc_offset} SECOND"
-                      end
+      date_interval = "INTERVAL '#{Time.zone.now.utc_offset} seconds'"
       Event.reorder(nil)
         .select(t[:project_id], t[:target_type], t[:action], "date(created_at + #{date_interval}) AS date", 'count(id) as total_amount')

lib/gitlab/database.rb

@@ -46,6 +46,7 @@ module Gitlab
       end
     end
+    # @deprecated
     def self.postgresql?
       adapter_name.casecmp('postgresql').zero?
     end
@@ -79,19 +80,19 @@ module Gitlab
     end
     def self.postgresql_9_or_less?
-      postgresql? && version.to_f < 10
+      version.to_f < 10
     end
     def self.join_lateral_supported?
-      postgresql? && version.to_f >= 9.3
+      version.to_f >= 9.3
     end
     def self.replication_slots_supported?
-      postgresql? && version.to_f >= 9.4
+      version.to_f >= 9.4
     end
     def self.postgresql_minimum_supported_version?
-      postgresql? && version.to_f >= 9.6
+      version.to_f >= 9.6
     end
     # map some of the function names that changed between PostgreSQL 9 and 10

lib/gitlab/database/grant.rb

@@ -6,47 +6,25 @@ module Gitlab
     class Grant < ActiveRecord::Base
       include FromUnion
-      self.table_name =
-        if Database.postgresql?
-          'information_schema.role_table_grants'
-        else
-          'information_schema.schema_privileges'
-        end
+      self.table_name = 'information_schema.role_table_grants'
       # Returns true if the current user can create and execute triggers on the
       # given table.
       def self.create_and_execute_trigger?(table)
-        if Database.postgresql?
-          # We _must not_ use quote_table_name as this will produce double
-          # quotes on PostgreSQL and for "has_table_privilege" we need single
-          # quotes.
-          quoted_table = connection.quote(table)
-
-          begin
-            from(nil)
-              .pluck(Arel.sql("has_table_privilege(#{quoted_table}, 'TRIGGER')"))
-              .first
-          rescue ActiveRecord::StatementInvalid
-            # This error is raised when using a non-existing table name. In this
-            # case we just want to return false as a user technically can't
-            # create triggers for such a table.
-            false
-          end
-        else
-          queries = [
-            Grant.select(1)
-              .from('information_schema.user_privileges')
-              .where("PRIVILEGE_TYPE = 'SUPER'")
-              .where("GRANTEE = CONCAT('\\'', REPLACE(CURRENT_USER(), '@', '\\'@\\''), '\\'')"),
-
-            Grant.select(1)
-              .from('information_schema.schema_privileges')
-              .where("PRIVILEGE_TYPE = 'TRIGGER'")
-              .where('TABLE_SCHEMA = ?', Gitlab::Database.database_name)
-              .where("GRANTEE = CONCAT('\\'', REPLACE(CURRENT_USER(), '@', '\\'@\\''), '\\'')")
-          ]
-          Grant.from_union(queries, alias_as: 'privs').any?
+        # We _must not_ use quote_table_name as this will produce double
+        # quotes on PostgreSQL and for "has_table_privilege" we need single
+        # quotes.
+        quoted_table = connection.quote(table)
+        begin
+          from(nil)
+            .pluck(Arel.sql("has_table_privilege(#{quoted_table}, 'TRIGGER')"))
+            .first
+        rescue ActiveRecord::StatementInvalid
+          # This error is raised when using a non-existing table name. In this
+          # case we just want to return false as a user technically can't
+          # create triggers for such a table.
+          false
         end
       end
     end

lib/gitlab/database/median.rb

@@ -137,8 +137,6 @@ module Gitlab
       end
       def extract_diff_epoch(diff)
-        return diff unless Gitlab::Database.postgresql?
-
         Arel.sql(%Q{EXTRACT(EPOCH FROM (#{diff.to_sql}))})
       end

lib/gitlab/database/migration_helpers.rb

@@ -152,8 +152,6 @@ module Gitlab
       # Only available on Postgresql >= 9.2
       def supports_drop_index_concurrently?
-        return false unless Database.postgresql?
-
         version = select_one("SELECT current_setting('server_version_num') AS v")['v'].to_i
         version >= 90200

lib/gitlab/database/sha_attribute.rb

@@ -2,14 +2,9 @@
 module Gitlab
   module Database
-    BINARY_TYPE =
-      if Gitlab::Database.postgresql?
-        # PostgreSQL defines its own class with slightly different
-        # behaviour from the default Binary type.
-        ActiveRecord::ConnectionAdapters::PostgreSQL::OID::Bytea
-      else
-        ActiveModel::Type::Binary
-      end
+    # PostgreSQL defines its own class with slightly different
+    # behaviour from the default Binary type.
+    BINARY_TYPE = ActiveRecord::ConnectionAdapters::PostgreSQL::OID::Bytea
     # Class for casting binary data to hexadecimal SHA1 hashes (and vice-versa).
     #

lib/gitlab/health_checks/db_check.rb

@@ -18,11 +18,7 @@ module Gitlab
         def check
           catch_timeout 10.seconds do
-            if Gitlab::Database.postgresql?
-              ActiveRecord::Base.connection.execute('SELECT 1 as ping')&.first&.[]('ping')&.to_s
-            else
-              ActiveRecord::Base.connection.execute('SELECT 1 as ping')&.first&.first&.to_s
-            end
+            ActiveRecord::Base.connection.execute('SELECT 1 as ping')&.first&.[]('ping')&.to_s
           end
         end
       end