From 505904f77b8420633d6840cb111ef70c2de66159 Mon Sep 17 00:00:00 2001
From: shantanualshi <shantanu.alshi@grafana.com>
Date: Thu, 4 Apr 2024 14:59:24 +0530
Subject: [PATCH] Bugfixes for detected  labels API

---
 pkg/ingester/ingester.go        |  4 ++--
 pkg/ingester/instance.go        |  2 --
 pkg/querier/ingester_querier.go | 19 +++++++++++++------
 pkg/querier/querier.go          |  8 +++++++-
 4 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/pkg/ingester/ingester.go b/pkg/ingester/ingester.go
index 244cd3b50d60e..937eceaa683e1 100644
--- a/pkg/ingester/ingester.go
+++ b/pkg/ingester/ingester.go
@@ -1389,7 +1389,7 @@ func (i *Ingester) GetDetectedLabels(ctx context.Context, req *logproto.Detected
 	}
 	var matchers []*labels.Matcher
 	if req.Query != "" {
-		matchers, err := syntax.ParseMatchers(req.Query, true)
+		matchers, err = syntax.ParseMatchers(req.Query, true)
 		if err != nil {
 			return nil, err
 		}
@@ -1403,7 +1403,7 @@ func (i *Ingester) GetDetectedLabels(ctx context.Context, req *logproto.Detected
 	}
 	result := make(map[string]*logproto.UniqueLabelValues)
 	for label, values := range labelMap {
-		uniqueValues := make([]string, len(values))
+		var uniqueValues []string
 		for v := range values {
 			uniqueValues = append(uniqueValues, v)
 		}
diff --git a/pkg/ingester/instance.go b/pkg/ingester/instance.go
index 5463eb16532b2..99bf587b21e85 100644
--- a/pkg/ingester/instance.go
+++ b/pkg/ingester/instance.go
@@ -564,8 +564,6 @@ func (i *instance) Label(ctx context.Context, req *logproto.LabelRequest, matche
 	}
 
 	labels := util.NewUniqueStrings(0)
-	// (shantanu) can create a map here to store label names::values and count the unique values
-	// just return a string to int map
 	err := i.forMatchingStreams(ctx, *req.Start, matchers, nil, func(s *stream) error {
 		for _, label := range s.labels {
 			if req.Values && label.Name == req.Name {
diff --git a/pkg/querier/ingester_querier.go b/pkg/querier/ingester_querier.go
index 68d88bbff4508..8b5b4d14a729e 100644
--- a/pkg/querier/ingester_querier.go
+++ b/pkg/querier/ingester_querier.go
@@ -370,17 +370,24 @@ func (q *IngesterQuerier) DetectedLabel(ctx context.Context, req *logproto.Detec
 	labelMap := make(map[string][]string)
 	for _, resp := range ingesterResponses {
 		thisIngester := resp.response.(*logproto.LabelToValuesResponse)
-		for label, values := range thisIngester.Labels {
-			uniqueValues := make([]string, len(values.Values))
-			allValues := thisIngester.Labels[label]
-			uniqueValues = append(uniqueValues, allValues.Values...)
 
-			labelMap[label] = uniqueValues
+		for label, thisIngesterValues := range thisIngester.Labels {
+			var combinedValues []string
+			allIngesterValues, isLabelPresent := labelMap[label]
+			if isLabelPresent {
+				combinedValues = append(allIngesterValues, thisIngesterValues.Values...)
+			} else {
+				combinedValues = thisIngesterValues.Values
+			}
+			labelMap[label] = combinedValues
 		}
 	}
+
+	// Dedupe all ingester values
 	mergedResult := make(map[string]*logproto.UniqueLabelValues)
 	for label, val := range labelMap {
-		uniqueValues := slices.CompactFunc(val, strings.EqualFold)
+		slices.Sort(val)
+		uniqueValues := slices.Compact(val)
 
 		mergedResult[label] = &logproto.UniqueLabelValues{
 			Values: uniqueValues,
diff --git a/pkg/querier/querier.go b/pkg/querier/querier.go
index dd550377d1a40..3c03cde0653b7 100644
--- a/pkg/querier/querier.go
+++ b/pkg/querier/querier.go
@@ -915,7 +915,7 @@ func (q *SingleTenantQuerier) DetectedLabels(ctx context.Context, req *logproto.
 
 	g, ctx := errgroup.WithContext(ctx)
 	ingesterQueryInterval, _ := q.buildQueryIntervals(*req.Start, *req.End)
-	if !q.cfg.QueryStoreOnly {
+	if !q.cfg.QueryStoreOnly && ingesterQueryInterval != nil {
 		g.Go(func() error {
 			var err error
 			splitReq := *req
@@ -932,6 +932,12 @@ func (q *SingleTenantQuerier) DetectedLabels(ctx context.Context, req *logproto.
 		return nil, err
 	}
 
+	if ingesterLabels == nil {
+		return &logproto.DetectedLabelsResponse{
+			DetectedLabels: []*logproto.DetectedLabel{},
+		}, nil
+	}
+
 	for label, values := range ingesterLabels.Labels {
 		if q.isLabelRelevant(label, values) {
 			detectedLabels = append(detectedLabels, &logproto.DetectedLabel{Label: label, Cardinality: uint64(len(values.Values))})