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.

2 files changed, 11 insertions, 31 deletions

diff --git a/app/finders/issuable_finder.rb b/app/finders/issuable_finder.rb
index f4fbeacfaba..1773ac2d508 100644
--- a/app/finders/issuable_finder.rb
+++ b/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)
 
diff --git a/app/finders/members_finder.rb b/app/finders/members_finder.rb
index 917de249104..f730b015c0a 100644
--- a/app/finders/members_finder.rb
+++ b/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