QFE: Fix @ modifier not being applied correctly on subqueries (thanos…

…-io#8016)

Signed-off-by: 🌲 Harry 🌊 John 🏔 <[email protected]>

CHANGELOG.md

@@ -13,6 +13,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 ### Fixed
 
 - [#7978](https://github.com/thanos-io/thanos/pull/7978) Receive: Fix deadlock during local writes when `split-tenant-label-name` is used
+- [#8016](https://github.com/thanos-io/thanos/pull/8016) Query Frontend: Fix @ modifier not being applied correctly on sub queries.
 
 ### Added
 

internal/cortex/querier/queryrange/split_by_interval.go

@@ -5,10 +5,11 @@ package queryrange
 
 import (
 	"context"
-	"github.com/thanos-io/thanos/pkg/extpromql"
 	"net/http"
 	"time"
 
+	"github.com/thanos-io/thanos/pkg/extpromql"
+
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/promauto"
 	"github.com/prometheus/prometheus/promql/parser"
@@ -112,6 +113,15 @@ func EvaluateAtModifierFunction(query string, start, end int64) (string, error)
 			}
 			selector.StartOrEnd = 0
 		}
+		if selector, ok := n.(*parser.SubqueryExpr); ok {
+			switch selector.StartOrEnd {
+			case parser.START:
+				selector.Timestamp = &start
+			case parser.END:
+				selector.Timestamp = &end
+			}
+			selector.StartOrEnd = 0
+		}
 		return nil
 	})
 	return expr.String(), err

internal/cortex/querier/queryrange/split_by_interval_test.go

@@ -374,6 +374,14 @@ func Test_evaluateAtModifier(t *testing.T) {
 				[2m:])
 			[10m:])`,
 		},
+		{
+			in:       `irate(kube_pod_info{namespace="test"}[1h:1m] @ start())`,
+			expected: `irate(kube_pod_info{namespace="test"}[1h:1m] @ 1546300.800)`,
+		},
+		{
+			in:       `irate(kube_pod_info{namespace="test"} @ end()[1h:1m] @ start())`,
+			expected: `irate(kube_pod_info{namespace="test"} @ 1646300.800 [1h:1m] @ 1546300.800)`,
+		},
 		{
 			// parse error: @ modifier must be preceded by an instant vector selector or range vector selector or a subquery
 			in:                "sum(http_requests_total[5m]) @ 10.001",