feat: Add optimizer hint syntax to set a priority in request options

Author: Connorhd

lib/arel/visitors/spanner.rb

@@ -91,10 +91,17 @@ def visit_Arel_Nodes_OptimizerHints o, collector
               StalenessHint.new min_read_timestamp: time
             next
           end
-          next unless v.start_with? "read_timestamp:"
-          time = Time.xmlschema v.delete_prefix("read_timestamp:")
-          collector.hints[:staleness] =
-            StalenessHint.new read_timestamp: time
+          if v.start_with? "read_timestamp:"
+            time = Time.xmlschema v.delete_prefix("read_timestamp:")
+            collector.hints[:staleness] =
+              StalenessHint.new read_timestamp: time
+            next
+          end
+          next unless v.start_with? "priority:"
+          priority = v.delete_prefix("priority:").strip.to_sym
+          collector.hints[:request_options] ||=
+            Google::Cloud::Spanner::V1::RequestOptions.new
+          collector.hints[:request_options].priority = priority
         end
         collector
       end

test/activerecord_spanner_mock_server/spanner_active_record_with_mock_server_test.rb

@@ -1067,6 +1067,19 @@ def test_join_hint
       assert_equal sql, execute_sql_request.sql
     end
 
+    def test_query_priority_hint
+      sql = "SELECT  `singers`.* FROM `singers`"
+      @mock.put_statement_result sql, MockServerTests::create_random_singers_result(4)
+      Singer.optimizer_hints("priority: PRIORITY_LOW").all.each do |singer|
+        refute_nil singer.id, "singer.id should not be nil"
+      end
+      select_requests = @mock.requests.select { |req| req.is_a?(Google::Cloud::Spanner::V1::ExecuteSqlRequest) && req.sql == sql }
+      select_requests.each do |request|
+        assert request.request_options
+        assert_equal :PRIORITY_LOW, request.request_options.priority
+      end
+    end
+
     def test_query_annotate_request_tag
       sql = "SELECT `singers`.* FROM `singers` /* request_tag: selecting all singers */"
       @mock.put_statement_result sql, MockServerTests::create_random_singers_result(4)
@@ -1080,6 +1093,20 @@ def test_query_annotate_request_tag
       end
     end
 
+    def test_query_priority_hint_and_request_tag
+      sql = "SELECT  `singers`.* FROM `singers` /* request_tag: selecting all singers */"
+      @mock.put_statement_result sql, MockServerTests::create_random_singers_result(4)
+      Singer.annotate("request_tag: selecting all singers").optimizer_hints("priority: PRIORITY_LOW").all.each do |singer|
+        refute_nil singer.id, "singer.id should not be nil"
+      end
+      select_requests = @mock.requests.select { |req| req.is_a?(Google::Cloud::Spanner::V1::ExecuteSqlRequest) && req.sql == sql }
+      select_requests.each do |request|
+        assert request.request_options
+        assert_equal :PRIORITY_LOW, request.request_options.priority
+        assert_equal "selecting all singers", request.request_options.request_tag
+      end
+    end
+
     def test_query_annotate_transaction_tag
       sql = "SELECT `singers`.* FROM `singers` /* transaction_tag: selecting all singers */"
       @mock.put_statement_result sql, MockServerTests::create_random_singers_result(4)