promql: pass down subquery interval (#11163)

If we are populating series for a subquery then set the interval
parameter accordingly so that downstream users could use that
information.

Signed-off-by: Giedrius Statkevičius <giedrius.statkevicius@vinted.com>

promql/engine.go

@@ -824,6 +824,20 @@ func (ng *Engine) getTimeRangesForSelector(s *parser.EvalStmt, n *parser.VectorS
 	return start, end
 }
 
+func (ng *Engine) getLastSubqueryInterval(path []parser.Node) time.Duration {
+	var interval time.Duration
+	for _, node := range path {
+		switch n := node.(type) {
+		case *parser.SubqueryExpr:
+			interval = n.Step
+			if n.Step == 0 {
+				interval = time.Duration(ng.noStepSubqueryIntervalFn(durationMilliseconds(n.Range))) * time.Millisecond
+			}
+		}
+	}
+	return interval
+}
+
 func (ng *Engine) populateSeries(querier storage.Querier, s *parser.EvalStmt) {
 	// Whenever a MatrixSelector is evaluated, evalRange is set to the corresponding range.
 	// The evaluation of the VectorSelector inside then evaluates the given range and unsets
@@ -834,10 +848,14 @@ func (ng *Engine) populateSeries(querier storage.Querier, s *parser.EvalStmt) {
 		switch n := node.(type) {
 		case *parser.VectorSelector:
 			start, end := ng.getTimeRangesForSelector(s, n, path, evalRange)
+			interval := ng.getLastSubqueryInterval(path)
+			if interval == 0 {
+				interval = s.Interval
+			}
 			hints := &storage.SelectHints{
 				Start: start,
 				End:   end,
-				Step:  durationMilliseconds(s.Interval),
+				Step:  durationMilliseconds(interval),
 				Range: durationMilliseconds(evalRange),
 				Func:  extractFuncFromPath(path),
 			}

promql/engine_test.go

@@ -330,56 +330,56 @@ func TestSelectHintsSetCorrectly(t *testing.T) {
 		}, {
 			query: "foo[2m:1s]", start: 300000,
 			expected: []*storage.SelectHints{
-				{Start: 175000, End: 300000},
+				{Start: 175000, End: 300000, Step: 1000},
 			},
 		}, {
 			query: "count_over_time(foo[2m:1s])", start: 300000,
 			expected: []*storage.SelectHints{
-				{Start: 175000, End: 300000, Func: "count_over_time"},
+				{Start: 175000, End: 300000, Func: "count_over_time", Step: 1000},
 			},
 		}, {
 			query: "count_over_time(foo[2m:1s] @ 300)", start: 200000,
 			expected: []*storage.SelectHints{
-				{Start: 175000, End: 300000, Func: "count_over_time"},
+				{Start: 175000, End: 300000, Func: "count_over_time", Step: 1000},
 			},
 		}, {
 			query: "count_over_time(foo[2m:1s] @ 200)", start: 200000,
 			expected: []*storage.SelectHints{
-				{Start: 75000, End: 200000, Func: "count_over_time"},
+				{Start: 75000, End: 200000, Func: "count_over_time", Step: 1000},
 			},
 		}, {
 			query: "count_over_time(foo[2m:1s] @ 100)", start: 200000,
 			expected: []*storage.SelectHints{
-				{Start: -25000, End: 100000, Func: "count_over_time"},
+				{Start: -25000, End: 100000, Func: "count_over_time", Step: 1000},
 			},
 		}, {
 			query: "count_over_time(foo[2m:1s] offset 10s)", start: 300000,
 			expected: []*storage.SelectHints{
-				{Start: 165000, End: 290000, Func: "count_over_time"},
+				{Start: 165000, End: 290000, Func: "count_over_time", Step: 1000},
 			},
 		}, {
 			query: "count_over_time((foo offset 10s)[2m:1s] offset 10s)", start: 300000,
 			expected: []*storage.SelectHints{
-				{Start: 155000, End: 280000, Func: "count_over_time"},
+				{Start: 155000, End: 280000, Func: "count_over_time", Step: 1000},
 			},
 		}, {
 			// When the @ is on the vector selector, the enclosing subquery parameters
 			// don't affect the hint ranges.
 			query: "count_over_time((foo @ 200 offset 10s)[2m:1s] offset 10s)", start: 300000,
 			expected: []*storage.SelectHints{
-				{Start: 185000, End: 190000, Func: "count_over_time"},
+				{Start: 185000, End: 190000, Func: "count_over_time", Step: 1000},
 			},
 		}, {
 			// When the @ is on the vector selector, the enclosing subquery parameters
 			// don't affect the hint ranges.
 			query: "count_over_time((foo @ 200 offset 10s)[2m:1s] @ 100 offset 10s)", start: 300000,
 			expected: []*storage.SelectHints{
-				{Start: 185000, End: 190000, Func: "count_over_time"},
+				{Start: 185000, End: 190000, Func: "count_over_time", Step: 1000},
 			},
 		}, {
 			query: "count_over_time((foo offset 10s)[2m:1s] @ 100 offset 10s)", start: 300000,
 			expected: []*storage.SelectHints{
-				{Start: -45000, End: 80000, Func: "count_over_time"},
+				{Start: -45000, End: 80000, Func: "count_over_time", Step: 1000},
 			},
 		}, {
 			query: "foo", start: 10000, end: 20000,
@@ -498,13 +498,13 @@ func TestSelectHintsSetCorrectly(t *testing.T) {
 		}, {
 			query: "(max by (dim1) (foo))[5s:1s]", start: 10000,
 			expected: []*storage.SelectHints{
-				{Start: 0, End: 10000, Func: "max", By: true, Grouping: []string{"dim1"}},
+				{Start: 0, End: 10000, Func: "max", By: true, Grouping: []string{"dim1"}, Step: 1000},
 			},
 		}, {
 			query: "(sum(http_requests{group=~\"p.*\"})+max(http_requests{group=~\"c.*\"}))[20s:5s]", start: 120000,
 			expected: []*storage.SelectHints{
-				{Start: 95000, End: 120000, Func: "sum", By: true},
-				{Start: 95000, End: 120000, Func: "max", By: true},
+				{Start: 95000, End: 120000, Func: "sum", By: true, Step: 5000},
+				{Start: 95000, End: 120000, Func: "max", By: true, Step: 5000},
 			},
 		}, {
 			query: "foo @ 50 + bar @ 250 + baz @ 900", start: 100000, end: 500000,
@@ -544,12 +544,12 @@ func TestSelectHintsSetCorrectly(t *testing.T) {
 		}, { // Hints are based on the inner most subquery timestamp.
 			query: `sum_over_time(sum_over_time(metric{job="1"}[100s])[100s:25s] @ 50)[3s:1s] @ 3000`, start: 100000,
 			expected: []*storage.SelectHints{
-				{Start: -150000, End: 50000, Range: 100000, Func: "sum_over_time"},
+				{Start: -150000, End: 50000, Range: 100000, Func: "sum_over_time", Step: 25000},
 			},
 		}, { // Hints are based on the inner most subquery timestamp.
 			query: `sum_over_time(sum_over_time(metric{job="1"}[100s])[100s:25s] @ 3000)[3s:1s] @ 50`,
 			expected: []*storage.SelectHints{
-				{Start: 2800000, End: 3000000, Range: 100000, Func: "sum_over_time"},
+				{Start: 2800000, End: 3000000, Range: 100000, Func: "sum_over_time", Step: 25000},
 			},
 		},
 	} {