Step-align end split from ingester query window

Signed-off-by: Danny Kopping <danny.kopping@grafana.com>

pkg/querier/queryrange/split_by_interval_test.go

@@ -412,8 +412,6 @@ func Test_splitQuery(t *testing.T) {
 
 					splits, err := intervals.splitter.split(refTime, []string{tenantID}, req, intervals.splitInterval)
 					require.NoError(t, err)
-					//require.Equal(t, want, splits)
-
 					if !assert.Equal(t, want, splits) {
 						t.Logf("expected and actual do not match\n")
 						defer t.Fail()
@@ -867,7 +865,7 @@ func Test_splitMetricQuery(t *testing.T) {
 				},
 				&LokiRequest{
 					StartTs: time.Date(2023, 1, 15, 5, 0, 0, 0, time.UTC),
-					EndTs:   time.Date(2023, 1, 15, 5, 5, 30, 0, time.UTC),
+					EndTs:   time.Date(2023, 1, 15, 5, 5, 15, 0, time.UTC),
 					Step:    15 * seconds,
 					Query:   shortRange,
 				},

pkg/querier/queryrange/splitters.go

@@ -217,7 +217,12 @@ func (s *metricQuerySplitter) split(execTime time.Time, tenantIDs []string, r qu
 		s.buildMetricSplits(lokiReq.GetStep(), ingesterQueryInterval, start, end, factory)
 
 		// rebound after ingester queries have been split out
-		end = start
+		//
+		// the end time should now be the boundary of the `query_ingester_within` window, which is "start" currently;
+		// but since start is already step-aligned we need to subtract 1ns to align it down by 1 more step so that we
+		// get a consistent step between splits
+		end, _ = s.alignStartEnd(r.GetStep(), start.Add(-time.Nanosecond), end)
+		// we restore the previous start time (the start time of the query)
 		start = origStart
 
 		// query only overlaps ingester query window, nothing more to do