Rename pg_stat_wal_receiver_supported? DB helper

From pg_stat_wal_receiver_supported? to
postgresql_minimum_supported_version?

Also add test coverage

lib/gitlab/database.rb

@@ -76,7 +76,7 @@ module Gitlab
       postgresql? && version.to_f >= 9.4
     end
-    def self.pg_stat_wal_receiver_supported?
+    def self.postgresql_minimum_supported_version?
       postgresql? && version.to_f >= 9.6
     end
@@ -98,6 +98,10 @@ module Gitlab
       Gitlab::Database.postgresql_9_or_less? ? 'pg_last_xlog_replay_location' : 'pg_last_wal_replay_lsn'
     end
+    def self.pg_last_xact_replay_timestamp
+      'pg_last_xact_replay_timestamp'
+    end
+
     def self.nulls_last_order(field, direction = 'ASC')
       order = "#{field} #{direction}"

spec/lib/gitlab/database_spec.rb

@@ -87,6 +87,38 @@ describe Gitlab::Database do
     end
   end
+  describe '.postgresql_minimum_supported_version?' do
+    it 'returns false when not using PostgreSQL' do
+      allow(described_class).to receive(:postgresql?).and_return(false)
+
+      expect(described_class.postgresql_minimum_supported_version?).to eq(false)
+    end
+
+    context 'when using PostgreSQL' do
+      before do
+        allow(described_class).to receive(:postgresql?).and_return(true)
+      end
+
+      it 'returns false when using PostgreSQL 9.5' do
+        allow(described_class).to receive(:version).and_return('9.5')
+
+        expect(described_class.postgresql_minimum_supported_version?).to eq(false)
+      end
+
+      it 'returns true when using PostgreSQL 9.6' do
+        allow(described_class).to receive(:version).and_return('9.6')
+
+        expect(described_class.postgresql_minimum_supported_version?).to eq(true)
+      end
+
+      it 'returns true when using PostgreSQL 10 or newer' do
+        allow(described_class).to receive(:version).and_return('10')
+
+        expect(described_class.postgresql_minimum_supported_version?).to eq(true)
+      end
+    end
+  end
+
   describe '.join_lateral_supported?' do
     it 'returns false when using MySQL' do
       allow(described_class).to receive(:postgresql?).and_return(false)
@@ -195,6 +227,12 @@ describe Gitlab::Database do
     end
   end
+  describe '.pg_last_xact_replay_timestamp' do
+    it 'returns pg_last_xact_replay_timestamp' do
+      expect(described_class.pg_last_xact_replay_timestamp).to eq('pg_last_xact_replay_timestamp')
+    end
+  end
+
   describe '.nulls_last_order' do
     context 'when using PostgreSQL' do
       before do