Address CR comments

Signed-off-by: Filip Petkovski <filip.petkovsky@gmail.com>

CHANGELOG.md

@@ -14,7 +14,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 ### Fixed
 - [#5502](https://github.com/thanos-io/thanos/pull/5502) Receive: Handle exemplar storage errors as conflict error.
 - [#5534](https://github.com/thanos-io/thanos/pull/5534) Query: Set struct return by query api alerts same as prometheus api.
-- [#5554](https://github.com/thanos-io/thanos/pull/5534) Query/Receiver: Fix querying exemplars from multi-tenant receivers.
+- [#5554](https://github.com/thanos-io/thanos/pull/5554) Query/Receiver: Fix querying exemplars from multi-tenant receivers.
 
 ### Added
 

pkg/exemplars/proxy.go

@@ -80,8 +80,10 @@ func (s *Proxy) Exemplars(req *exemplarspb.ExemplarsRequest, srv exemplarspb.Exe
 		exemplars []*exemplarspb.ExemplarData
 	)
 
+	queryParts := make([]string, 0)
+	labelMatchers := make([]string, 0)
 	for _, st := range s.exemplars() {
-		var queryParts []string
+		queryParts = queryParts[:0]
 
 	Matchers:
 		for _, matchers := range selectors {
@@ -102,12 +104,12 @@ func (s *Proxy) Exemplars(req *exemplarspb.ExemplarsRequest, srv exemplarspb.Exe
 				}
 			}
 
-			matchers := make([]string, 0, len(matcherSet))
+			labelMatchers = labelMatchers[:0]
 			for m := range matcherSet {
-				matchers = append(matchers, m)
+				labelMatchers = append(labelMatchers, m)
 			}
 
-			queryParts = append(queryParts, "{"+strings.Join(matchers, ", ")+"}")
+			queryParts = append(queryParts, "{"+strings.Join(labelMatchers, ", ")+"}")
 		}
 
 		// No matchers match this store.

pkg/exemplars/proxy_test.go

@@ -12,20 +12,18 @@ import (
 	"sync"
 	"testing"
 
-	"github.com/prometheus/prometheus/promql/parser"
-	"google.golang.org/grpc/codes"
-	"google.golang.org/grpc/status"
-
 	"github.com/go-kit/log"
 	"github.com/pkg/errors"
 	"github.com/prometheus/prometheus/model/labels"
-	"go.uber.org/atomic"
-	"google.golang.org/grpc"
-
+	"github.com/prometheus/prometheus/promql/parser"
 	"github.com/thanos-io/thanos/pkg/exemplars/exemplarspb"
 	"github.com/thanos-io/thanos/pkg/store/labelpb"
 	"github.com/thanos-io/thanos/pkg/store/storepb"
 	"github.com/thanos-io/thanos/pkg/testutil"
+	"go.uber.org/atomic"
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 )
 
 type testExemplarClient struct {