Disable scalar for vertical sharding

Signed-off-by: Justin Jung <jungjust@amazon.com>

CHANGELOG.md

@@ -25,6 +25,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 ### Changed
 - [#6168](https://github.com/thanos-io/thanos/pull/6168) Receiver: Make ketama hashring fail early when configured with number of nodes lower than the replication factor.
 - [#6201](https://github.com/thanos-io/thanos/pull/6201) Query-Frontend: Disable absent and absent_over_time for vertical sharding.
+- [#6212](https://github.com/thanos-io/thanos/pull/6212) Query-Frontend: Disable scalar for vertical sharding.
 
 ### Removed
 

pkg/querysharding/analyzer.go

@@ -105,7 +105,7 @@ func (a *QueryAnalyzer) Analyze(query string) (QueryAnalysis, error) {
 				if n.Func.Name == "label_join" || n.Func.Name == "label_replace" {
 					dstLabel := stringFromArg(n.Args[1])
 					dynamicLabels = append(dynamicLabels, dstLabel)
-				} else if n.Func.Name == "absent_over_time" || n.Func.Name == "absent" {
+				} else if n.Func.Name == "absent_over_time" || n.Func.Name == "absent" || n.Func.Name == "scalar" {
 					isShardable = false
 					return notShardableErr
 				}

pkg/querysharding/analyzer_test.go

@@ -75,6 +75,10 @@ http_requests_total`,
 			name:       "absent is not shardable",
 			expression: `sum by (url) (absent(http_requests_total{code="400"}))`,
 		},
+		{
+			name:       "scalar is not shardable",
+			expression: `scalar(sum by (url) (http_requests_total{code="400"}))`,
+		},
 	}
 
 	shardableByLabels := []testCase{