Merge pull request #17141 from prometheus/beorn7/histogram3

promql: Use `HistogramStatsIterator` more often

promql/bench_test.go

@@ -350,6 +350,14 @@ func BenchmarkNativeHistograms(b *testing.B) {
 			name:  "histogram_count with long rate interval",
 			query: "histogram_count(sum(rate(native_histogram_series[20m])))",
 		},
+		{
+			name:  "two-legged histogram_count/sum with short rate interval",
+			query: "histogram_count(sum(rate(native_histogram_series[2m]))) + histogram_sum(sum(rate(native_histogram_series[2m])))",
+		},
+		{
+			name:  "two-legged histogram_count/sum with long rate interval",
+			query: "histogram_count(sum(rate(native_histogram_series[20m]))) + histogram_sum(sum(rate(native_histogram_series[20m])))",
+		},
 	}
 
 	opts := promql.EngineOpts{

promql/engine.go

@@ -3920,7 +3920,7 @@ func detectHistogramStatsDecoding(expr parser.Expr) {
 				break pathLoop
 			}
 		}
-		return errors.New("stop")
+		return nil
 	})
 }
 

promql/promqltest/testdata/native_histograms.test

@@ -1660,3 +1660,20 @@ eval instant at 30s histogram_count(avg(reset))
 eval instant at 5m histogram_count(rate(reset{timing="late"}[5m]))
     expect no_warn
     {timing="late"} 0.0175
+
+clear
+
+# Test edge cases of HistogramStatsIterator detection.
+# We access the same series multiple times within the same expression,
+# once with and once without HistogramStatsIterator. The results here
+# at least prove that we do not use HistogramStatsIterator where we
+# should not.
+load 1m
+     histogram {{schema:0 count:10 sum:50 counter_reset_hint:gauge buckets:[1 2 3 4]}}
+
+eval instant at 1m histogram_count(histogram unless histogram_quantile(0.5, histogram) < 3)
+     {} 10
+
+eval instant at 1m histogram_quantile(0.5, histogram unless histogram_count(histogram) == 0)
+     {} 3.1748021039363987
+