[v9.5.x] Prometheus: Fix regression for $__rate_interval comparison (#67505)

Prometheus: Fix regression for $__rate_interval comparison (#67460)

* fix ,  comparison regression

* intervalMs was not pressent before the regression and this value changes the adjusted interval calculating giving a false positive in favor of the regression

(cherry picked from commit d4a22cff0a)

Co-authored-by: Brendan O'Handley <brendan.ohandley@grafana.com>

pkg/tsdb/prometheus/models/query.go

@@ -156,6 +156,10 @@ func calculatePrometheusInterval(
 	query backend.DataQuery,
 	intervalCalculator intervalv2.Calculator,
 ) (time.Duration, error) {
+	// we need to compare the original query model after it is overwritten below to variables so that we can
+	// calculate the rateInterval if it is equal to $__rate_interval or ${__rate_interval}
+	originalQueryInterval := queryInterval
+
 	// If we are using variable for interval/step, we will replace it with calculated interval
 	if isVariableInterval(queryInterval) {
 		queryInterval = ""
@@ -173,7 +177,8 @@ func calculatePrometheusInterval(
 		adjustedInterval = calculatedInterval.Value
 	}
 
-	if queryInterval == varRateInterval || queryInterval == varRateIntervalAlt {
+	// here is where we compare for $__rate_interval or ${__rate_interval}
+	if originalQueryInterval == varRateInterval || originalQueryInterval == varRateIntervalAlt {
 		// Rate interval is final and is not affected by resolution
 		return calculateRateInterval(adjustedInterval, timeInterval, intervalCalculator), nil
 	} else {

pkg/tsdb/prometheus/models/query_test.go

@@ -376,7 +376,6 @@ func TestParse(t *testing.T) {
 			"format": "time_series",
 			"intervalFactor": 1,
 			"interval": "$__rate_interval",
-			"intervalMs": 60000,
 			"refId": "A"
 		}`, timeRange)