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.

3 files changed, 18 insertions, 49 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