Remove check for availability of PG upsert

With >= PG11, this is not necessary anymore

lib/gitlab/database.rb

@@ -107,10 +107,6 @@ module Gitlab
       version.to_f >= MINIMUM_POSTGRES_VERSION
     end
 
-    def self.upsert_supported?
-      version.to_f >= 9.5
-    end
-
     def self.check_postgres_version_and_print_warning
       return if Gitlab::Database.postgresql_minimum_supported_version?
       return if Gitlab::Runtime.rails_runner?
@@ -221,9 +217,7 @@ module Gitlab
         VALUES #{tuples.map { |tuple| "(#{tuple.join(', ')})" }.join(', ')}
       EOF
 
-      if upsert_supported? && on_conflict == :do_nothing
-        sql = "#{sql} ON CONFLICT DO NOTHING"
-      end
+      sql = "#{sql} ON CONFLICT DO NOTHING" if on_conflict == :do_nothing
 
       sql = "#{sql} RETURNING id" if return_ids
 

spec/lib/gitlab/database_spec.rb

@@ -283,7 +283,6 @@ RSpec.describe Gitlab::Database do
   describe '.bulk_insert' do
     before do
       allow(described_class).to receive(:connection).and_return(connection)
-      allow(described_class).to receive(:version).and_return(version)
       allow(connection).to receive(:quote_column_name, &:itself)
       allow(connection).to receive(:quote, &:itself)
       allow(connection).to receive(:execute)
@@ -298,8 +297,6 @@ RSpec.describe Gitlab::Database do
       ]
     end
 
-    let_it_be(:version) { 9.6 }
-
     it 'does nothing with empty rows' do
       expect(connection).not_to receive(:execute)
 
@@ -366,28 +363,13 @@ RSpec.describe Gitlab::Database do
         expect(ids).to eq([10])
       end
 
-      context 'with version >= 9.5' do
-        it 'allows setting the upsert to do nothing' do
-          expect(connection)
-            .to receive(:execute)
-            .with(/ON CONFLICT DO NOTHING/)
-
-          described_class
-            .bulk_insert('test', [{ number: 10 }], on_conflict: :do_nothing)
-        end
-      end
-
-      context 'with version < 9.5' do
-        let(:version) { 9.4 }
-
-        it 'refuses setting the upsert' do
-          expect(connection)
-            .not_to receive(:execute)
-            .with(/ON CONFLICT/)
+      it 'allows setting the upsert to do nothing' do
+        expect(connection)
+          .to receive(:execute)
+          .with(/ON CONFLICT DO NOTHING/)
 
-          described_class
-            .bulk_insert('test', [{ number: 10 }], on_conflict: :do_nothing)
-        end
+        described_class
+          .bulk_insert('test', [{ number: 10 }], on_conflict: :do_nothing)
       end
     end
   end