make aggregations deterministic (#9459)

* Add deterministic test for aggregations

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

* Make aggregations deterministic

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

* Increase testing

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

promql/engine.go

@@ -2138,6 +2138,7 @@ type groupedAggregation struct {
 func (ev *evaluator) aggregation(op parser.ItemType, grouping []string, without bool, param interface{}, vec Vector, seriesHelper []EvalSeriesHelper, enh *EvalNodeHelper) Vector {
 
 	result := map[uint64]*groupedAggregation{}
+	orderedResult := []*groupedAggregation{}
 	var k int64
 	if op == parser.TOPK || op == parser.BOTTOMK {
 		f := param.(float64)
@@ -2206,12 +2207,16 @@ func (ev *evaluator) aggregation(op parser.ItemType, grouping []string, without
 			} else {
 				m = metric.WithLabels(grouping...)
 			}
-			result[groupingKey] = &groupedAggregation{
+			newAgg := &groupedAggregation{
 				labels:     m,
 				value:      s.V,
 				mean:       s.V,
 				groupCount: 1,
 			}
+
+			result[groupingKey] = newAgg
+			orderedResult = append(orderedResult, newAgg)
+
 			inputVecLen := int64(len(vec))
 			resultSize := k
 			if k > inputVecLen {
@@ -2333,7 +2338,7 @@ func (ev *evaluator) aggregation(op parser.ItemType, grouping []string, without
 	}
 
 	// Construct the result Vector from the aggregated groups.
-	for _, aggr := range result {
+	for _, aggr := range orderedResult {
 		switch op {
 		case parser.AVG:
 			aggr.value = aggr.mean

promql/testdata/aggregators.test

@@ -497,3 +497,13 @@ eval instant at 1m avg(data{test="-big"})
 
 eval instant at 1m avg(data{test="bigzero"})
 	{} 0
+
+clear
+
+# Test that aggregations are deterministic.
+load 10s
+	up{job="prometheus"} 1
+	up{job="prometheus2"} 1
+
+eval instant at 1m count(topk(1,max(up) without()) == topk(1,max(up) without()) == topk(1,max(up) without()) == topk(1,max(up) without()) == topk(1,max(up) without()))
+	{} 1