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.

13 files changed, 47 insertions, 129 deletions

diff --git a/lib/gitlab/background_migration/migrate_stage_index.rb b/lib/gitlab/background_migration/migrate_stage_index.rb
index f921233460d..55608529cee 100644
--- a/lib/gitlab/background_migration/migrate_stage_index.rb
+++ b/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
-            )
+        <<~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
+          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
diff --git a/lib/gitlab/background_migration/prepare_untracked_uploads.rb b/lib/gitlab/background_migration/prepare_untracked_uploads.rb
index 806c3a7a369..2ac51dd7b55 100644
--- a/lib/gitlab/background_migration/prepare_untracked_uploads.rb
+++ b/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
 
diff --git a/lib/gitlab/background_migration/remove_restricted_todos.rb b/lib/gitlab/background_migration/remove_restricted_todos.rb
index 47579d46c1b..9ef6d8654ae 100644
--- a/lib/gitlab/background_migration/remove_restricted_todos.rb
+++ b/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
 
diff --git a/lib/gitlab/ci/charts.rb b/lib/gitlab/ci/charts.rb
index 7cabaadb122..3fbfdffe277 100644
--- a/lib/gitlab/ci/charts.rb
+++ b/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
 
diff --git a/lib/gitlab/contributions_calendar.rb b/lib/gitlab/contributions_calendar.rb
index f7d046600e8..5b0b91de5da 100644
--- a/lib/gitlab/contributions_calendar.rb
+++ b/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')
diff --git a/lib/gitlab/database.rb b/lib/gitlab/database.rb
index eef63536de4..cbdff0ab060 100644
--- a/lib/gitlab/database.rb
+++ b/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
diff --git a/lib/gitlab/database/grant.rb b/lib/gitlab/database/grant.rb
index 26adf4e221b..1f47f320a29 100644
--- a/lib/gitlab/database/grant.rb
+++ b/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(), '@', '\\'@\\''), '\\'')")
-          ]
+        # 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)
 
-          Grant.from_union(queries, alias_as: 'privs').any?
+        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
diff --git a/lib/gitlab/database/median.rb b/lib/gitlab/database/median.rb
index 391c1e85a7d..603b125d8b4 100644
--- a/lib/gitlab/database/median.rb
+++ b/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
 
diff --git a/lib/gitlab/database/migration_helpers.rb b/lib/gitlab/database/migration_helpers.rb
index 4bd09163bf2..9bba4f6ce1e 100644
--- a/lib/gitlab/database/migration_helpers.rb
+++ b/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
diff --git a/lib/gitlab/database/sha_attribute.rb b/lib/gitlab/database/sha_attribute.rb
index 109ae7893da..ddbabc9098e 100644
--- a/lib/gitlab/database/sha_attribute.rb
+++ b/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).
     #
diff --git a/lib/gitlab/health_checks/db_check.rb b/lib/gitlab/health_checks/db_check.rb
index 2bcd25cd3cc..ec4b97eaca4 100644
--- a/lib/gitlab/health_checks/db_check.rb
+++ b/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
diff --git a/lib/gitlab/sherlock/query.rb b/lib/gitlab/sherlock/query.rb
index 159ce27e702..cbd89b7629f 100644
--- a/lib/gitlab/sherlock/query.rb
+++ b/lib/gitlab/sherlock/query.rb
@@ -96,12 +96,7 @@ module Gitlab
       private
 
       def raw_explain(query)
-        explain =
-          if Gitlab::Database.postgresql?
-            "EXPLAIN ANALYZE #{query};"
-          else
-            "EXPLAIN #{query};"
-          end
+        explain = "EXPLAIN ANALYZE #{query};"
 
         ActiveRecord::Base.connection.execute(explain)
       end
diff --git a/lib/tasks/gitlab/setup.rake b/lib/tasks/gitlab/setup.rake
index e763de682f8..5d86d6e466c 100644
--- a/lib/tasks/gitlab/setup.rake
+++ b/lib/tasks/gitlab/setup.rake
@@ -45,8 +45,6 @@ namespace :gitlab do
   # method terminates all the connections so that a subsequent DROP
   # will work.
   def self.terminate_all_connections
-    return false unless Gitlab::Database.postgresql?
-
     cmd = <<~SQL
     SELECT pg_terminate_backend(pg_stat_activity.pid)
         FROM pg_stat_activity