refactor(stringlabels): Support stringlabels in `logql/log` package (#17838)

This is another step towards supporting Prometheus' stringlabels implementation in Loki. It adds support in the `logql/log` package.

Part of https://github.com/grafana/loki/issues/17122

The tests should now compile and pass with `-tags stringlabels`.

---
Co-authored-by: Karsten Jeschkies <karsten.jeschkies@grafana.com>

pkg/chunkenc/memchunk.go

@@ -1317,7 +1317,7 @@ func (hb *headBlock) SampleIterator(
 	for _, e := range hb.entries {
 		for _, extractor := range extractors {
 			stats.AddHeadChunkBytes(int64(len(e.s)))
-			samples, ok := extractor.ProcessString(e.t, e.s, e.structuredMetadata...)
+			samples, ok := extractor.ProcessString(e.t, e.s, e.structuredMetadata)
 			if !ok || len(samples) == 0 {
 				continue
 			}
@@ -1769,7 +1769,7 @@ func (e *sampleBufferedIterator) Next() bool {
 	for e.bufferedIterator.Next() {
 		e.stats.AddPostFilterLines(1)
 
-		samples, ok := e.extractor.Process(e.currTs, e.currLine, e.currStructuredMetadata...)
+		samples, ok := e.extractor.Process(e.currTs, e.currLine, e.currStructuredMetadata)
 		if !ok || len(samples) == 0 {
 			continue
 		}

pkg/chunkenc/memchunk_test.go

@@ -527,7 +527,7 @@ func TestSerialization(t *testing.T) {
 							require.Equal(t, labels.FromStrings("foo", strconv.Itoa(i)), logproto.FromLabelAdaptersToLabels(e.StructuredMetadata))
 						} else {
 							require.Equal(t, labels.EmptyLabels().String(), it.Labels())
-							require.Nil(t, e.StructuredMetadata)
+							require.Empty(t, logproto.FromLabelAdaptersToLabels(e.StructuredMetadata))
 						}
 					}
 					require.NoError(t, it.Err())

pkg/chunkenc/symbols_test.go

@@ -161,32 +161,32 @@ func TestSymbolizerLabelNormalization(t *testing.T) {
 		{
 			name: "basic label normalization",
 			labelsToAdd: []labels.Labels{
-				{
-					{Name: "foo-bar", Value: "value1"},
-					{Name: "fizz_buzz", Value: "value2"},
-				},
+				labels.FromStrings(
+					"foo-bar", "value1",
+					"fizz_buzz", "value2",
+				),
 			},
 			expectedLabels: []labels.Labels{
-				{
-					{Name: "foo_bar", Value: "value1"},
-					{Name: "fizz_buzz", Value: "value2"},
-				},
+				labels.FromStrings(
+					"foo_bar", "value1",
+					"fizz_buzz", "value2",
+				),
 			},
 			description: "hyphens should be converted to underscores in label names",
 		},
 		{
 			name: "same string as name and value",
 			labelsToAdd: []labels.Labels{
-				{
-					{Name: "foo-bar", Value: "foo-bar"},
-					{Name: "fizz-buzz", Value: "fizz-buzz"},
-				},
+				labels.FromStrings(
+					"foo-bar", "foo-bar",
+					"fizz-buzz", "fizz-buzz",
+				),
 			},
 			expectedLabels: []labels.Labels{
-				{
-					{Name: "foo_bar", Value: "foo-bar"},
-					{Name: "fizz_buzz", Value: "fizz-buzz"},
-				},
+				labels.FromStrings(
+					"foo_bar", "foo-bar",
+					"fizz_buzz", "fizz-buzz",
+				),
 			},
 			description: "only normalize when string is used as a name, not as a value",
 		},
@@ -267,10 +267,10 @@ func TestSymbolizerLabelNormalizationAfterCheckpointing(t *testing.T) {
 	s := newSymbolizer()
 
 	// Add some labels and serialize them
-	originalLabels := labels.Labels{
-		{Name: "foo-bar", Value: "value1"},
-		{Name: "fizz-buzz", Value: "value2"},
-	}
+	originalLabels := labels.FromStrings(
+		"foo-bar", "value1",
+		"fizz-buzz", "value2",
+	)
 	_, err := s.Add(originalLabels)
 	require.NoError(t, err)
 
@@ -282,19 +282,21 @@ func TestSymbolizerLabelNormalizationAfterCheckpointing(t *testing.T) {
 	loaded := symbolizerFromCheckpoint(buf.Bytes())
 
 	// Add new labels with the same names but different values
-	newLabels := labels.Labels{
-		{Name: "foo-bar", Value: "new-value1"},
-		{Name: "fizz-buzz", Value: "new-value2"},
-	}
+	newLabels := labels.FromStrings(
+		"foo-bar", "new-value1",
+		"fizz-buzz", "new-value2",
+	)
 	symbols, err := loaded.Add(newLabels)
 	require.NoError(t, err)
 
 	// Check that the normalization is consistent
 	result := loaded.Lookup(symbols, nil)
-	require.Equal(t, "foo_bar", result[0].Name, "first label should be normalized")
-	require.Equal(t, "new-value1", result[0].Value, "first value should be unchanged")
-	require.Equal(t, "fizz_buzz", result[1].Name, "second label should be normalized")
-	require.Equal(t, "new-value2", result[1].Value, "second value should be unchanged")
+	expected := map[string]string{
+		"foo_bar":   "new-value1",
+		"fizz_buzz": "new-value2",
+	}
+
+	require.Equal(t, expected, result.Map(), "label names should be normalized")
 }
 
 func TestSymbolizerLabelNormalizationSameNameValue(t *testing.T) {

pkg/chunkenc/unordered.go

@@ -333,7 +333,7 @@ func (hb *unorderedHeadBlock) SampleIterator(
 			structuredMetadata = hb.symbolizer.Lookup(structuredMetadataSymbols, labelsBuilder)
 
 			for _, extractor := range extractor {
-				samples, ok := extractor.ProcessString(ts, line, structuredMetadata...)
+				samples, ok := extractor.ProcessString(ts, line, structuredMetadata)
 				if !ok || len(samples) == 0 {
 					return nil
 				}

pkg/chunkenc/unordered_test.go

@@ -26,9 +26,7 @@ func iterEq(t *testing.T, exp []entry, got iter.EntryIterator) {
 			Timestamp:          time.Unix(0, exp[i].t),
 			Line:               exp[i].s,
 			StructuredMetadata: logproto.FromLabelsToLabelAdapters(exp[i].structuredMetadata),
-		}
-		if exp[i].structuredMetadata.IsEmpty() {
-			expected.StructuredMetadata = nil
+			Parsed:             logproto.EmptyLabelAdapters(),
 		}
 		require.Equal(t, expected, got.At())
 		require.Equal(t, exp[i].structuredMetadata.String(), got.Labels())
@@ -729,20 +727,24 @@ func TestReorderAcrossBlocks(t *testing.T) {
 
 	exp := []entry{
 		{
-			t: time.Unix(1, 0).UnixNano(),
-			s: "1",
+			t:                  time.Unix(1, 0).UnixNano(),
+			s:                  "1",
+			structuredMetadata: labels.EmptyLabels(),
 		},
 		{
-			t: time.Unix(3, 0).UnixNano(),
-			s: "3",
+			t:                  time.Unix(3, 0).UnixNano(),
+			s:                  "3",
+			structuredMetadata: labels.EmptyLabels(),
 		},
 		{
-			t: time.Unix(5, 0).UnixNano(),
-			s: "5",
+			t:                  time.Unix(5, 0).UnixNano(),
+			s:                  "5",
+			structuredMetadata: labels.EmptyLabels(),
 		},
 		{
-			t: time.Unix(7, 0).UnixNano(),
-			s: "7",
+			t:                  time.Unix(7, 0).UnixNano(),
+			s:                  "7",
+			structuredMetadata: labels.EmptyLabels(),
 		},
 	}
 	iterEq(t, exp, itr)

pkg/chunkenc/variants.go

@@ -58,7 +58,7 @@ func (e *multiExtractorSampleBufferedIterator) Next() bool {
 		e.stats.AddPostFilterLines(1)
 
 		for _, extractor := range e.extractors {
-			samples, ok := extractor.Process(e.currTs, e.currLine, e.currStructuredMetadata...)
+			samples, ok := extractor.Process(e.currTs, e.currLine, e.currStructuredMetadata)
 			if !ok || len(samples) == 0 {
 				continue
 			}

pkg/compactor/retention/retention_test.go

@@ -631,6 +631,7 @@ func TestChunkRewriter(t *testing.T) {
 							Timestamp:          curr.Time(),
 							Line:               curr.String(),
 							StructuredMetadata: logproto.FromLabelsToLabelAdapters(expectedStructuredMetadata),
+							Parsed:             logproto.EmptyLabelAdapters(),
 						}, newChunkItr.At())
 						require.Equal(t, expectedStructuredMetadata.String(), newChunkItr.Labels())
 					}

pkg/dataobj/querier/iter.go

@@ -252,7 +252,7 @@ func newSampleIterator(ctx context.Context,
 				timestamp := record.Timestamp.UnixNano()
 
 				statistics.AddDecompressedLines(1)
-				samples, ok := streamExtractor.Process(timestamp, record.Line, record.Metadata...)
+				samples, ok := streamExtractor.Process(timestamp, record.Line, record.Metadata)
 				if !ok {
 					continue
 				}

pkg/dataobj/querier/store_test.go

@@ -377,8 +377,21 @@ func TestStore_SelectLogs(t *testing.T) {
 		},
 	}
 
+	emptyLabelAdapters := logproto.EmptyLabelAdapters()
+
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
+			// Make sure all empty label sets use an empty slice, rather than nil, to make assertions below easier.
+			for i := range tt.want {
+				if len(tt.want[i].Entry.Parsed) == 0 {
+					tt.want[i].Entry.Parsed = emptyLabelAdapters
+				}
+
+				if len(tt.want[i].Entry.StructuredMetadata) == 0 {
+					tt.want[i].Entry.StructuredMetadata = emptyLabelAdapters
+				}
+			}
+
 			it, err := store.SelectLogs(ctx, logql.SelectLogParams{
 				QueryRequest: &logproto.QueryRequest{
 					Start:     tt.start,

pkg/ingester/checkpoint_test.go

@@ -424,12 +424,16 @@ var (
 		Labels: labels.FromStrings("stream", "1").String(),
 		Entries: []logproto.Entry{
 			{
-				Timestamp: time.Unix(0, 1),
-				Line:      "1",
+				Timestamp:          time.Unix(0, 1),
+				Line:               "1",
+				StructuredMetadata: logproto.EmptyLabelAdapters(),
+				Parsed:             logproto.EmptyLabelAdapters(),
 			},
 			{
-				Timestamp: time.Unix(0, 2),
-				Line:      "2",
+				Timestamp:          time.Unix(0, 2),
+				Line:               "2",
+				StructuredMetadata: logproto.EmptyLabelAdapters(),
+				Parsed:             logproto.EmptyLabelAdapters(),
 			},
 		},
 	}
@@ -437,12 +441,16 @@ var (
 		Labels: labels.FromStrings("stream", "2").String(),
 		Entries: []logproto.Entry{
 			{
-				Timestamp: time.Unix(0, 1),
-				Line:      "3",
+				Timestamp:          time.Unix(0, 1),
+				Line:               "3",
+				StructuredMetadata: logproto.EmptyLabelAdapters(),
+				Parsed:             logproto.EmptyLabelAdapters(),
 			},
 			{
-				Timestamp: time.Unix(0, 2),
-				Line:      "4",
+				Timestamp:          time.Unix(0, 2),
+				Line:               "4",
+				StructuredMetadata: logproto.EmptyLabelAdapters(),
+				Parsed:             logproto.EmptyLabelAdapters(),
 			},
 		},
 	}

pkg/ingester/flush_test.go

@@ -568,6 +568,19 @@ func buildTestStreams(offset int) []logproto.Stream {
 // check that the store is holding data equivalent to what we expect
 func (s *testStore) checkData(t *testing.T, testData map[string][]logproto.Stream) {
 	for userID, expected := range testData {
+		// Ensure all empty label sets use an empty set of adapters, rather than a nil slice, to make the assertion below easier.
+		for _, stream := range expected {
+			for i := range stream.Entries {
+				if len(stream.Entries[i].Parsed) == 0 {
+					stream.Entries[i].Parsed = logproto.EmptyLabelAdapters()
+				}
+
+				if len(stream.Entries[i].StructuredMetadata) == 0 {
+					stream.Entries[i].StructuredMetadata = logproto.EmptyLabelAdapters()
+				}
+			}
+		}
+
 		streams := s.getStreamsForUser(t, userID)
 		require.Equal(t, expected, streams)
 	}

pkg/ingester/instance_test.go

@@ -1035,14 +1035,14 @@ func (p *mockStreamExtractor) BaseLabels() log.LabelsResult {
 	return p.wrappedSP.BaseLabels()
 }
 
-func (p *mockStreamExtractor) Process(ts int64, line []byte, lbs ...labels.Label) ([]log.ExtractedSample, bool) {
+func (p *mockStreamExtractor) Process(ts int64, line []byte, lbs labels.Labels) ([]log.ExtractedSample, bool) {
 	p.called++
-	return p.wrappedSP.Process(ts, line, lbs...)
+	return p.wrappedSP.Process(ts, line, lbs)
 }
 
-func (p *mockStreamExtractor) ProcessString(ts int64, line string, lbs ...labels.Label) ([]log.ExtractedSample, bool) {
+func (p *mockStreamExtractor) ProcessString(ts int64, line string, lbs labels.Labels) ([]log.ExtractedSample, bool) {
 	p.called++
-	return p.wrappedSP.ProcessString(ts, line, lbs...)
+	return p.wrappedSP.ProcessString(ts, line, lbs)
 }
 
 func Test_QueryWithDelete(t *testing.T) {

pkg/ingester/recovery_test.go

@@ -294,8 +294,10 @@ func TestSeriesRecoveryNoDuplicates(t *testing.T) {
 			Labels: lbls.String(),
 			Entries: []logproto.Entry{
 				{
-					Timestamp: time.Unix(1, 0),
-					Line:      "line 1",
+					Timestamp:          time.Unix(1, 0),
+					Line:               "line 1",
+					StructuredMetadata: logproto.EmptyLabelAdapters(),
+					Parsed:             logproto.EmptyLabelAdapters(),
 				},
 			},
 			Hash: lbls.Hash(),

pkg/ingester/tailer_test.go

@@ -315,9 +315,10 @@ func Test_StructuredMetadata(t *testing.T) {
 						Labels: labels.NewBuilder(lbs).Set("foo", "1").Labels().String(),
 						Entries: []logproto.Entry{
 							{
-								Timestamp: time.Unix(0, 1),
-								Line:      "foo=1",
-								Parsed:    logproto.FromLabelsToLabelAdapters(labels.FromStrings("foo", "1")),
+								Timestamp:          time.Unix(0, 1),
+								Line:               "foo=1",
+								Parsed:             logproto.FromLabelsToLabelAdapters(labels.FromStrings("foo", "1")),
+								StructuredMetadata: logproto.EmptyLabelAdapters(),
 							},
 						},
 					},

pkg/logproto/compat.go

@@ -61,6 +61,10 @@ func FromLabelsToLabelAdapters(ls labels.Labels) []LabelAdapter {
 	return *(*[]LabelAdapter)(unsafe.Pointer(&ls)) // #nosec G103 -- we know the string is not mutated
 }
 
+func EmptyLabelAdapters() []LabelAdapter {
+	return FromLabelsToLabelAdapters(labels.EmptyLabels())
+}
+
 // FromLabelAdaptersToMetric converts []LabelAdapter to a model.Metric.
 // Don't do this on any performance sensitive paths.
 func FromLabelAdaptersToMetric(ls []LabelAdapter) model.Metric {

pkg/logql/log/consolidated_variant_extractor.go

@@ -37,7 +37,7 @@ func (c *consolidatedMultiVariantStreamExtractor) BaseLabels() LabelsResult {
 	return c.commonPipeline.BaseLabels()
 }
 
-func (c *consolidatedMultiVariantStreamExtractor) Process(ts int64, line []byte, structuredMetadata ...labels.Label) ([]ExtractedSample, bool) {
+func (c *consolidatedMultiVariantStreamExtractor) Process(ts int64, line []byte, structuredMetadata labels.Labels) ([]ExtractedSample, bool) {
 	// Process the line through the common pipeline
 	processedLine, commonLabels, ok := c.commonPipeline.Process(ts, line, structuredMetadata)
 	if !ok {
@@ -57,7 +57,7 @@ func (c *consolidatedMultiVariantStreamExtractor) Process(ts int64, line []byte,
 	lbls := commonLabels.Labels()
 	for i, variant := range c.variants {
 		streamVariantExtractor := variant.ForStream(lbls)
-		samples, ok := streamVariantExtractor.Process(ts, processedLine, commonStructuredMetadata...)
+		samples, ok := streamVariantExtractor.Process(ts, processedLine, commonStructuredMetadata)
 		if ok {
 			for _, sample := range samples {
 				sample.Labels = appendVariantLabel(sample.Labels, i)
@@ -74,14 +74,15 @@ func (c *consolidatedMultiVariantStreamExtractor) Process(ts int64, line []byte,
 }
 
 func appendVariantLabel(lbls LabelsResult, variantIndex int) LabelsResult {
-	streamLbls := lbls.Stream()
+	newLblsBuilder := labels.NewScratchBuilder(lbls.Stream().Len() + 1)
 
-	newLbls := make(labels.Labels, 0, len(streamLbls)+1)
-	newLbls = append(newLbls, labels.Label{
-		Name:  constants.VariantLabel,
-		Value: strconv.Itoa(variantIndex),
+	lbls.Stream().Range(func(l labels.Label) {
+		newLblsBuilder.Add(l.Name, l.Value)
 	})
-	newLbls = append(newLbls, streamLbls...)
+
+	newLblsBuilder.Add(constants.VariantLabel, strconv.Itoa(variantIndex))
+	newLblsBuilder.Sort()
+	newLbls := newLblsBuilder.Labels()
 
 	builder := NewBaseLabelsBuilder().ForLabels(newLbls, newLbls.Hash())
 	builder.Add(StructuredMetadataLabel, lbls.StructuredMetadata())
@@ -89,8 +90,8 @@ func appendVariantLabel(lbls LabelsResult, variantIndex int) LabelsResult {
 	return builder.LabelsResult()
 }
 
-func (c *consolidatedMultiVariantStreamExtractor) ProcessString(ts int64, line string, structuredMetadata ...labels.Label) ([]ExtractedSample, bool) {
-	return c.Process(ts, unsafeGetBytes(line), structuredMetadata...)
+func (c *consolidatedMultiVariantStreamExtractor) ProcessString(ts int64, line string, structuredMetadata labels.Labels) ([]ExtractedSample, bool) {
+	return c.Process(ts, unsafeGetBytes(line), structuredMetadata)
 }
 
 func (c *consolidatedMultiVariantStreamExtractor) ReferencedStructuredMetadata() bool {

pkg/logql/log/consolidated_variant_extractor_test.go

@@ -34,12 +34,10 @@ func Test_ConsolidatedMultiVariantExtractor(t *testing.T) {
 		// Attempt to create a consolidated multi-variant extractor
 		// This will fail because the function doesn't exist yet
 		extractor := NewConsolidatedMultiVariantExtractor(commonPipeline, variants)
-		streamExtractor := extractor.ForStream(labels.Labels{
-			{Name: "foo", Value: "bar"},
-		})
+		streamExtractor := extractor.ForStream(labels.FromStrings("foo", "bar"))
 
 		// Process a log line
-		samples, ok := streamExtractor.ProcessString(1000, "test log line")
+		samples, ok := streamExtractor.ProcessString(1000, "test log line", labels.EmptyLabels())
 		require.True(t, ok)
 		require.Len(t, samples, 2)
 
@@ -80,8 +78,8 @@ func (m *MockCommonPipeline) Reset() {
 	panic("not implemented") // TODO: Implement
 }
 
-func (m *MockCommonPipeline) ForStream(labels labels.Labels) StreamPipeline {
-	lblsResult := NewLabelsResult(labels.String(), labels.Hash(), labels, nil, nil)
+func (m *MockCommonPipeline) ForStream(lbls labels.Labels) StreamPipeline {
+	lblsResult := NewLabelsResult(lbls.String(), lbls.Hash(), lbls, labels.EmptyLabels(), labels.EmptyLabels())
 	return &MockCommonStreamPipeline{
 		counter:       m.counter,
 		shouldPass:    m.shouldPass,
@@ -122,8 +120,8 @@ type MockVariantSpecificExtractor struct {
 	shouldExtract  bool
 }
 
-func (m *MockVariantSpecificExtractor) ForStream(labels labels.Labels) StreamSampleExtractor {
-	lblsResult := NewLabelsResult(labels.String(), labels.Hash(), labels, nil, nil)
+func (m *MockVariantSpecificExtractor) ForStream(lbls labels.Labels) StreamSampleExtractor {
+	lblsResult := NewLabelsResult(lbls.String(), lbls.Hash(), lbls, labels.EmptyLabels(), labels.EmptyLabels())
 	return &mockVariantSpecificStreamExtractor{
 		valueToExtract: m.valueToExtract,
 		shouldExtract:  m.shouldExtract,
@@ -142,7 +140,7 @@ func (m *mockVariantSpecificStreamExtractor) BaseLabels() LabelsResult {
 	panic("not implemented") // TODO: Implement
 }
 
-func (m *mockVariantSpecificStreamExtractor) Process(_ int64, _ []byte, _ ...labels.Label) ([]ExtractedSample, bool) {
+func (m *mockVariantSpecificStreamExtractor) Process(_ int64, _ []byte, _ labels.Labels) ([]ExtractedSample, bool) {
 	result := []ExtractedSample{
 		{
 			Value:  m.valueToExtract,
@@ -153,8 +151,8 @@ func (m *mockVariantSpecificStreamExtractor) Process(_ int64, _ []byte, _ ...lab
 	return result, m.shouldExtract
 }
 
-func (m *mockVariantSpecificStreamExtractor) ProcessString(ts int64, line string, lbls ...labels.Label) ([]ExtractedSample, bool) {
-	return m.Process(ts, []byte(line), lbls...)
+func (m *mockVariantSpecificStreamExtractor) ProcessString(ts int64, line string, lbls labels.Labels) ([]ExtractedSample, bool) {
+	return m.Process(ts, []byte(line), lbls)
 }
 
 func (m *mockVariantSpecificStreamExtractor) ReferencedStructuredMetadata() bool {

pkg/logql/log/fmt_test.go

@@ -711,47 +711,47 @@ func Test_labelsFormatter_Format(t *testing.T) {
 		{
 			"unixToTime days",
 			mustNewLabelsFormatter([]LabelFmt{NewTemplateLabelFmt("foo", `{{ .bar | unixToTime }}`)}),
-			labels.Labels{{Name: "foo", Value: ""}, {Name: "bar", Value: "19503"}},
-			labels.Labels{
-				{Name: "bar", Value: "19503"},
-				{Name: "foo", Value: epochDay19503.String()},
-			},
+			labels.FromStrings("foo", "", "bar", "19503"),
+			labels.FromStrings(
+				"bar", "19503",
+				"foo", epochDay19503.String(),
+			),
 		},
 		{
 			"unixToTime seconds",
 			mustNewLabelsFormatter([]LabelFmt{NewTemplateLabelFmt("foo", `{{ .bar | unixToTime }}`)}),
-			labels.Labels{{Name: "foo", Value: ""}, {Name: "bar", Value: "1679577215"}},
-			labels.Labels{
-				{Name: "bar", Value: "1679577215"},
-				{Name: "foo", Value: epochSeconds1679577215.String()},
-			},
+			labels.FromStrings("foo", "", "bar", "1679577215"),
+			labels.FromStrings(
+				"bar", "1679577215",
+				"foo", epochSeconds1679577215.String(),
+			),
 		},
 		{
 			"unixToTime milliseconds",
 			mustNewLabelsFormatter([]LabelFmt{NewTemplateLabelFmt("foo", `{{ .bar | unixToTime }}`)}),
-			labels.Labels{{Name: "foo", Value: ""}, {Name: "bar", Value: "1257894000000"}},
-			labels.Labels{
-				{Name: "bar", Value: "1257894000000"},
-				{Name: "foo", Value: epochMilliseconds1257894000000.String()},
-			},
+			labels.FromStrings("foo", "", "bar", "1257894000000"),
+			labels.FromStrings(
+				"bar", "1257894000000",
+				"foo", epochMilliseconds1257894000000.String(),
+			),
 		},
 		{
 			"unixToTime microseconds",
 			mustNewLabelsFormatter([]LabelFmt{NewTemplateLabelFmt("foo", `{{ .bar | unixToTime }}`)}),
-			labels.Labels{{Name: "foo", Value: ""}, {Name: "bar", Value: "1673798889902000"}},
-			labels.Labels{
-				{Name: "bar", Value: "1673798889902000"},
-				{Name: "foo", Value: epochMicroseconds1673798889902000.String()},
-			},
+			labels.FromStrings("foo", "", "bar", "1673798889902000"),
+			labels.FromStrings(
+				"bar", "1673798889902000",
+				"foo", epochMicroseconds1673798889902000.String(),
+			),
 		},
 		{
 			"unixToTime nanoseconds",
 			mustNewLabelsFormatter([]LabelFmt{NewTemplateLabelFmt("foo", `{{ .bar | unixToTime }}`)}),
-			labels.Labels{{Name: "foo", Value: ""}, {Name: "bar", Value: "1000000000000000000"}},
-			labels.Labels{
-				{Name: "bar", Value: "1000000000000000000"},
-				{Name: "foo", Value: epochNanoseconds1000000000000000000.String()},
-			},
+			labels.FromStrings("foo", "", "bar", "1000000000000000000"),
+			labels.FromStrings(
+				"bar", "1000000000000000000",
+				"foo", epochNanoseconds1000000000000000000.String(),
+			),
 		},
 	}
 

pkg/logql/log/label_filter_test.go

@@ -385,25 +385,25 @@ func TestStringLabelFilter(t *testing.T) {
 		{
 			name:        `logfmt|msg=~"(?i)hello" (with label)`,
 			filter:      NewStringLabelFilter(labels.MustNewMatcher(labels.MatchRegexp, "msg", "(?i)hello")),
-			labels:      labels.Labels{{Name: "msg", Value: "HELLO"}, {Name: "subqueries", Value: ""}}, // label `msg` contains HELLO
+			labels:      labels.FromStrings("msg", "HELLO", "subqueries", ""), // label `msg` contains HELLO
 			shouldMatch: true,
 		},
 		{
 			name:        `logfmt|msg=~"(?i)hello" (with label)`,
 			filter:      NewStringLabelFilter(labels.MustNewMatcher(labels.MatchRegexp, "msg", "(?i)hello")),
-			labels:      labels.Labels{{Name: "msg", Value: "hello"}, {Name: "subqueries", Value: ""}}, // label `msg` contains hello
+			labels:      labels.FromStrings("msg", "hello", "subqueries", ""), // label `msg` contains hello
 			shouldMatch: true,
 		},
 		{
 			name:        `logfmt|msg=~"(?i)HELLO" (with label)`,
 			filter:      NewStringLabelFilter(labels.MustNewMatcher(labels.MatchRegexp, "msg", "(?i)HELLO")),
-			labels:      labels.Labels{{Name: "msg", Value: "HELLO"}, {Name: "subqueries", Value: ""}}, // label `msg` contains HELLO
+			labels:      labels.FromStrings("msg", "HELLO", "subqueries", ""), // label `msg` contains HELLO
 			shouldMatch: true,
 		},
 		{
 			name:        `logfmt|msg=~"(?i)HELLO" (with label)`,
 			filter:      NewStringLabelFilter(labels.MustNewMatcher(labels.MatchRegexp, "msg", "(?i)HELLO")),
-			labels:      labels.Labels{{Name: "msg", Value: "hello"}, {Name: "subqueries", Value: ""}}, // label `msg` contains hello
+			labels:      labels.FromStrings("msg", "hello", "subqueries", ""), // label `msg` contains hello
 			shouldMatch: true,
 		},
 	}

pkg/logql/log/labels.go

@@ -2,9 +2,6 @@ package log
 
 import (
 	"fmt"
-	"slices"
-	"sort"
-	"strings"
 	"sync"
 
 	"github.com/prometheus/prometheus/model/labels"
@@ -53,7 +50,21 @@ func (l labelsResult) String() string {
 }
 
 func (l labelsResult) Labels() labels.Labels {
-	return flattenLabels(nil, l.stream, l.structuredMetadata, l.parsed)
+	size := l.stream.Len() + l.structuredMetadata.Len() + l.parsed.Len()
+	b := labels.NewScratchBuilder(size)
+
+	l.stream.Range(func(l labels.Label) {
+		b.Add(l.Name, l.Value)
+	})
+	l.structuredMetadata.Range(func(l labels.Label) {
+		b.Add(l.Name, l.Value)
+	})
+	l.parsed.Range(func(l labels.Label) {
+		b.Add(l.Name, l.Value)
+	})
+
+	b.Sort()
+	return b.Labels()
 }
 
 func (l labelsResult) Hash() uint64 {
@@ -61,44 +72,17 @@ func (l labelsResult) Hash() uint64 {
 }
 
 func (l labelsResult) Stream() labels.Labels {
-	if len(l.stream) == 0 {
-		return nil
-	}
 	return l.stream
 }
 
 func (l labelsResult) StructuredMetadata() labels.Labels {
-	if len(l.structuredMetadata) == 0 {
-		return nil
-	}
 	return l.structuredMetadata
 }
 
 func (l labelsResult) Parsed() labels.Labels {
-	if len(l.parsed) == 0 {
-		return nil
-	}
 	return l.parsed
 }
 
-type hasher struct {
-	buf []byte // buffer for computing hash without bytes slice allocation.
-}
-
-// newHasher allow to compute hashes for labels by reusing the same buffer.
-func newHasher() *hasher {
-	return &hasher{
-		buf: make([]byte, 0, 1024),
-	}
-}
-
-// Hash hashes the labels
-func (h *hasher) Hash(lbs labels.Labels) uint64 {
-	var hash uint64
-	hash, h.buf = lbs.HashWithoutLabels(h.buf, []string(nil)...)
-	return hash
-}
-
 type LabelCategory int
 
 const (
@@ -129,7 +113,7 @@ func categoriesContain(categories []LabelCategory, category LabelCategory) bool
 // Only one base builder is used and it contains cache for each LabelsBuilders.
 type BaseLabelsBuilder struct {
 	del []string
-	add [numValidCategories]labels.Labels
+	add [numValidCategories][]labels.Label
 	// nolint:structcheck
 	// https://github.com/golangci/golangci-lint/issues/826
 	err string
@@ -150,7 +134,7 @@ type BaseLabelsBuilder struct {
 // LabelsBuilder is the same as labels.Builder but tailored for this package.
 type LabelsBuilder struct {
 	base          labels.Labels
-	buf           labels.Labels
+	buf           []labels.Label
 	currentResult LabelsResult
 	groupedResult LabelsResult
 
@@ -166,10 +150,10 @@ func NewBaseLabelsBuilderWithGrouping(groups []string, parserKeyHints ParserHint
 	const labelsCapacity = 16
 	return &BaseLabelsBuilder{
 		del: make([]string, 0, 5),
-		add: [numValidCategories]labels.Labels{
-			StreamLabel:             make(labels.Labels, 0, labelsCapacity),
-			StructuredMetadataLabel: make(labels.Labels, 0, labelsCapacity),
-			ParsedLabel:             make(labels.Labels, 0, labelsCapacity),
+		add: [numValidCategories][]labels.Label{
+			StreamLabel:             make([]labels.Label, 0, labelsCapacity),
+			StructuredMetadataLabel: make([]labels.Label, 0, labelsCapacity),
+			ParsedLabel:             make([]labels.Label, 0, labelsCapacity),
 		},
 		resultCache:    make(map[uint64]LabelsResult),
 		hasher:         newHasher(),
@@ -315,11 +299,12 @@ func (b *LabelsBuilder) getWithCategory(key string) (string, LabelCategory, bool
 		}
 	}
 
-	for _, l := range b.base {
-		if l.Name == key {
-			return l.Value, StreamLabel, true
-		}
+	value := b.base.Get(key)
+
+	if value != "" {
+		return value, StreamLabel, true
 	}
+
 	return "", InvalidCategory, false
 }
 
@@ -437,15 +422,7 @@ func (b *LabelsBuilder) GetJSONPath(labelName string) []string {
 	return path
 }
 
-// Labels returns the labels from the builder. If no modifications
-// were made, the original labels are returned.
-func (b *LabelsBuilder) labels(categories ...LabelCategory) labels.Labels {
-	b.buf = b.UnsortedLabels(b.buf, categories...)
-	sort.Sort(b.buf)
-	return b.buf
-}
-
-func (b *LabelsBuilder) appendErrors(buf labels.Labels) labels.Labels {
+func (b *LabelsBuilder) appendErrors(buf []labels.Label) []labels.Label {
 	if b.err != "" {
 		buf = append(buf, labels.Label{
 			Name:  logqlmodel.ErrorLabel,
@@ -461,18 +438,22 @@ func (b *LabelsBuilder) appendErrors(buf labels.Labels) labels.Labels {
 	return buf
 }
 
-func (b *LabelsBuilder) UnsortedLabels(buf labels.Labels, categories ...LabelCategory) labels.Labels {
+func (b *LabelsBuilder) UnsortedLabels(buf []labels.Label, categories ...LabelCategory) []labels.Label {
 	if categories == nil {
 		categories = allCategories
 	}
 
 	if !b.hasDel() && !b.hasAdd() && categoriesContain(categories, StreamLabel) {
 		if buf == nil {
-			buf = make(labels.Labels, 0, len(b.base)+1) // +1 for error label.
+			buf = make([]labels.Label, 0, b.base.Len()+1) // +1 for error label.
 		} else {
 			buf = buf[:0]
 		}
-		buf = append(buf, b.base...)
+
+		b.base.Range(func(l labels.Label) {
+			buf = append(buf, l)
+		})
+
 		if categoriesContain(categories, ParsedLabel) {
 			buf = b.appendErrors(buf)
 		}
@@ -483,39 +464,38 @@ func (b *LabelsBuilder) UnsortedLabels(buf labels.Labels, categories ...LabelCat
 	// In the general case, labels are removed, modified or moved
 	// rather than added.
 	if buf == nil {
-		size := len(b.base) + b.sizeAdd() + 1
-		buf = make(labels.Labels, 0, size)
+		size := b.base.Len() + b.sizeAdd() + 1
+		buf = make([]labels.Label, 0, size)
 	} else {
 		buf = buf[:0]
 	}
 
 	if categoriesContain(categories, StreamLabel) {
-	Outer:
-		for _, l := range b.base {
+		b.base.Range(func(l labels.Label) {
 			// Skip stream labels to be deleted
 			for _, n := range b.del {
 				if l.Name == n {
-					continue Outer
+					return
 				}
 			}
 
 			// Skip stream labels which value will be replaced by structured metadata
 			if labelsContain(b.add[StructuredMetadataLabel], l.Name) {
-				continue
+				return
 			}
 
 			// Skip stream labels which value will be replaced by parsed labels
 			if labelsContain(b.add[ParsedLabel], l.Name) {
-				continue
+				return
 			}
 
 			// Take value from stream label if present
-			if labelsContain(b.add[StreamLabel], l.Name) {
-				buf = append(buf, labels.Label{Name: l.Name, Value: b.add[StreamLabel].Get(l.Name)})
+			if value, found := findLabelValue(b.add[StreamLabel], l.Name); found {
+				buf = append(buf, labels.Label{Name: l.Name, Value: value})
 			} else {
 				buf = append(buf, l)
 			}
-		}
+		})
 	}
 
 	if categoriesContain(categories, StructuredMetadataLabel) {
@@ -611,9 +591,8 @@ func (b *LabelsBuilder) LabelsResult() LabelsResult {
 
 	// Get all labels at once and sort them
 	b.buf = b.UnsortedLabels(b.buf)
-	// sort.Sort(b.buf)
-	slices.SortFunc(b.buf, func(a, b labels.Label) int { return strings.Compare(a.Name, b.Name) })
-	hash := b.hasher.Hash(b.buf)
+	lbls := labels.New(b.buf...)
+	hash := b.hasher.Hash(lbls)
 
 	if cached, ok := b.resultCache[hash]; ok {
 		return cached
@@ -639,47 +618,38 @@ func (b *LabelsBuilder) LabelsResult() LabelsResult {
 		}
 	}
 
-	result := NewLabelsResult(b.buf.String(), hash, labels.New(stream...), labels.New(meta...), labels.New(parsed...))
+	result := NewLabelsResult(lbls.String(), hash, labels.New(stream...), labels.New(meta...), labels.New(parsed...))
 	b.resultCache[hash] = result
 
 	return result
 }
 
-func flattenLabels(buf labels.Labels, many ...labels.Labels) labels.Labels {
-	var size int
-	for _, lbls := range many {
-		size += len(lbls)
-	}
-
-	if buf == nil || cap(buf) < size {
-		buf = make(labels.Labels, 0, size)
-	} else {
-		buf = buf[:0]
-	}
-
-	for _, lbls := range many {
-		buf = append(buf, lbls...)
+func labelsContain(labels []labels.Label, name string) bool {
+	for _, l := range labels {
+		if l.Name == name {
+			return true
+		}
 	}
-	sort.Sort(buf)
-	return buf
+	return false
 }
 
-func labelsContain(labels labels.Labels, name string) bool {
+func findLabelValue(labels []labels.Label, name string) (string, bool) {
 	for _, l := range labels {
 		if l.Name == name {
-			return true
+			return l.Value, true
 		}
 	}
-	return false
+	return "", false
 }
 
-func (b *BaseLabelsBuilder) toUncategorizedResult(buf labels.Labels) LabelsResult {
-	hash := b.hasher.Hash(buf)
+func (b *BaseLabelsBuilder) toUncategorizedResult(buf []labels.Label) LabelsResult {
+	lbls := labels.New(buf...)
+	hash := b.hasher.Hash(lbls)
 	if cached, ok := b.resultCache[hash]; ok {
 		return cached
 	}
 
-	res := NewLabelsResult(buf.String(), hash, buf.Copy(), nil, nil)
+	res := NewLabelsResult(lbls.String(), hash, lbls, labels.EmptyLabels(), labels.EmptyLabels())
 	b.resultCache[hash] = res
 	return res
 }
@@ -714,7 +684,7 @@ func (b *LabelsBuilder) GroupedLabels() LabelsResult {
 
 func (b *LabelsBuilder) withResult() LabelsResult {
 	if b.buf == nil {
-		b.buf = make(labels.Labels, 0, len(b.groups))
+		b.buf = make([]labels.Label, 0, len(b.groups))
 	} else {
 		b.buf = b.buf[:0]
 	}
@@ -736,11 +706,10 @@ Outer:
 				}
 			}
 		}
-		for _, l := range b.base {
-			if g == l.Name {
-				b.buf = append(b.buf, l)
-				continue Outer
-			}
+
+		value := b.base.Get(g)
+		if value != "" {
+			b.buf = append(b.buf, labels.Label{Name: g, Value: value})
 		}
 	}
 	return b.toUncategorizedResult(b.buf)
@@ -748,35 +717,35 @@ Outer:
 
 func (b *LabelsBuilder) withoutResult() LabelsResult {
 	if b.buf == nil {
-		size := len(b.base) + b.sizeAdd() - len(b.del) - len(b.groups)
+		size := b.base.Len() + b.sizeAdd() - len(b.del) - len(b.groups)
 		if size < 0 {
 			size = 0
 		}
-		b.buf = make(labels.Labels, 0, size)
+		b.buf = make([]labels.Label, 0, size)
 	} else {
 		b.buf = b.buf[:0]
 	}
-Outer:
-	for _, l := range b.base {
+
+	b.base.Range(func(l labels.Label) {
 		for _, n := range b.del {
 			if l.Name == n {
-				continue Outer
+				return
 			}
 		}
 		for _, lbls := range b.add {
 			for _, la := range lbls {
 				if l.Name == la.Name {
-					continue Outer
+					return
 				}
 			}
 		}
 		for _, lg := range b.groups {
 			if l.Name == lg {
-				continue Outer
+				return
 			}
 		}
 		b.buf = append(b.buf, l)
-	}
+	})
 
 	for category, lbls := range b.add {
 	OuterAdd:
@@ -792,7 +761,7 @@ Outer:
 			b.buf = append(b.buf, la)
 		}
 	}
-	sort.Sort(b.buf)
+
 	return b.toUncategorizedResult(b.buf)
 }
 
@@ -806,7 +775,7 @@ func (b *LabelsBuilder) toBaseGroup() LabelsResult {
 	} else {
 		lbs = labels.NewBuilder(b.base).Keep(b.groups...).Labels()
 	}
-	res := NewLabelsResult(lbs.String(), lbs.Hash(), lbs, nil, nil)
+	res := NewLabelsResult(lbs.String(), lbs.Hash(), lbs, labels.EmptyLabels(), labels.EmptyLabels())
 	b.groupedResult = res
 	return res
 }
@@ -831,26 +800,3 @@ func (i internedStringSet) Get(data []byte, createNew func() (string, bool)) (st
 	}{s: newStr, ok: ok}
 	return newStr, ok
 }
-
-// BufferedLabelsBuilder is a simple builder that uses a label buffer passed in.
-// It is used to avoid allocations when building labels.
-type BufferedLabelsBuilder struct {
-	buf labels.Labels
-}
-
-func NewBufferedLabelsBuilder(labels labels.Labels) *BufferedLabelsBuilder {
-	return &BufferedLabelsBuilder{buf: labels[:0]}
-}
-
-func (b *BufferedLabelsBuilder) Reset() {
-	b.buf = b.buf[:0]
-}
-
-func (b *BufferedLabelsBuilder) Add(label labels.Label) {
-	b.buf = append(b.buf, label)
-}
-
-func (b *BufferedLabelsBuilder) Labels() labels.Labels {
-	//slices.SortFunc(b.buf, func(a, b labels.Label) int { return strings.Compare(a.Name, b.Name) })
-	return b.buf
-}

pkg/logql/log/labels_slicelabels.go

@@ -0,0 +1,47 @@
+//go:build !stringlabels && !dedupelabels
+
+package log
+
+import "github.com/prometheus/prometheus/model/labels"
+
+type hasher struct {
+	buf []byte // buffer for computing hash without bytes slice allocation.
+}
+
+// newHasher returns a hasher that computes hashes for labels by reusing the same buffer.
+func newHasher() *hasher {
+	return &hasher{
+		buf: make([]byte, 0, 1024),
+	}
+}
+
+// Hash computes a hash of lbs.
+// It is not guaranteed to be stable across different Loki processes or versions.
+func (h *hasher) Hash(lbs labels.Labels) uint64 {
+	var hash uint64
+	hash, h.buf = lbs.HashWithoutLabels(h.buf, []string(nil)...)
+	return hash
+}
+
+// BufferedLabelsBuilder is a simple builder that uses a label buffer passed in.
+// It is used to avoid allocations when building labels.
+type BufferedLabelsBuilder struct {
+	buf labels.Labels
+}
+
+func NewBufferedLabelsBuilder(labels labels.Labels) *BufferedLabelsBuilder {
+	return &BufferedLabelsBuilder{buf: labels[:0]}
+}
+
+func (b *BufferedLabelsBuilder) Reset() {
+	b.buf = b.buf[:0]
+}
+
+func (b *BufferedLabelsBuilder) Add(label labels.Label) {
+	b.buf = append(b.buf, label)
+}
+
+func (b *BufferedLabelsBuilder) Labels() labels.Labels {
+	//slices.SortFunc(b.buf, func(a, b labels.Label) int { return strings.Compare(a.Name, b.Name) })
+	return b.buf
+}

pkg/logql/log/labels_stringlabels.go

@@ -0,0 +1,43 @@
+//go:build stringlabels
+
+package log
+
+import "github.com/prometheus/prometheus/model/labels"
+
+type hasher struct{}
+
+// newHasher returns a hasher that computes hashes for labels.
+func newHasher() *hasher {
+	return &hasher{}
+}
+
+// Hash computes a hash of lbs.
+// It is not guaranteed to be stable across different Loki processes or versions.
+func (h *hasher) Hash(lbs labels.Labels) uint64 {
+	// We use Hash() here because there's no performance advantage to using HashWithoutLabels() with stringlabels.
+	// The results from Hash(l) and HashWithoutLabels(l, []string{}) are different with stringlabels, so using Hash
+	// here also simplifies our tests.
+	return lbs.Hash()
+}
+
+// BufferedLabelsBuilder is a simple builder that uses a label buffer passed in.
+// It is used to avoid allocations when building labels.
+type BufferedLabelsBuilder struct {
+	builder *labels.Builder
+}
+
+func NewBufferedLabelsBuilder(l labels.Labels) *BufferedLabelsBuilder {
+	return &BufferedLabelsBuilder{builder: labels.NewBuilder(l)}
+}
+
+func (b *BufferedLabelsBuilder) Reset() {
+	b.builder.Reset(labels.EmptyLabels())
+}
+
+func (b *BufferedLabelsBuilder) Add(label labels.Label) {
+	b.builder.Set(label.Name, label.Value)
+}
+
+func (b *BufferedLabelsBuilder) Labels() labels.Labels {
+	return b.builder.Labels()
+}

pkg/logql/log/labels_test.go

@@ -2,7 +2,8 @@ package log
 
 import (
 	"fmt"
-	"sort"
+	"slices"
+	"strings"
 	"testing"
 	"time"
 
@@ -64,7 +65,7 @@ func TestLabelsBuilder_LabelsError(t *testing.T) {
 	require.Equal(t, expectedLbs.String(), lbsWithErr.String())
 	require.Equal(t, expectedLbs.Hash(), lbsWithErr.Hash())
 	require.Equal(t, labels.FromStrings("already", "in"), lbsWithErr.Stream())
-	require.Nil(t, lbsWithErr.StructuredMetadata())
+	require.Equal(t, labels.EmptyLabels(), lbsWithErr.StructuredMetadata())
 	require.Equal(t, labels.FromStrings(logqlmodel.ErrorLabel, "err"), lbsWithErr.Parsed())
 
 	// make sure the original labels is unchanged.
@@ -89,7 +90,7 @@ func TestLabelsBuilder_LabelsErrorFromAdd(t *testing.T) {
 	require.Equal(t, expectedLbs.String(), lbsWithErr.String())
 	require.Equal(t, expectedLbs.Hash(), lbsWithErr.Hash())
 	require.Equal(t, labels.FromStrings("already", "in"), lbsWithErr.Stream())
-	require.Nil(t, lbsWithErr.StructuredMetadata())
+	require.Equal(t, labels.EmptyLabels(), lbsWithErr.StructuredMetadata())
 	require.Equal(t, labels.FromStrings(logqlmodel.ErrorLabel, "test error", logqlmodel.ErrorDetailsLabel, "test details"), lbsWithErr.Parsed())
 
 	// make sure the original labels is unchanged.
@@ -187,11 +188,8 @@ func TestLabelsBuilder_LabelsResult(t *testing.T) {
 		"buzz", "fuzz",
 		"ToReplace", "other",
 	)
-	expected := make(labels.Labels, 0, len(expectedStreamLbls)+len(expectedStucturedMetadataLbls)+len(expectedParsedLbls))
-	expected = append(expected, expectedStreamLbls...)
-	expected = append(expected, expectedStucturedMetadataLbls...)
-	expected = append(expected, expectedParsedLbls...)
-	expected = labels.New(expected...)
+
+	expected := mergeLabels(expectedStreamLbls, expectedStucturedMetadataLbls, expectedParsedLbls)
 
 	assertLabelResult(t, expected, b.LabelsResult())
 	// cached.
@@ -220,11 +218,7 @@ func TestLabelsBuilder_LabelsResult(t *testing.T) {
 		"ToReplace", "other",
 	)
 
-	expected = make(labels.Labels, 0, len(expectedStreamLbls)+len(expectedStucturedMetadataLbls)+len(expectedParsedLbls))
-	expected = append(expected, expectedStreamLbls...)
-	expected = append(expected, expectedStucturedMetadataLbls...)
-	expected = append(expected, expectedParsedLbls...)
-	expected = labels.New(expected...)
+	expected = mergeLabels(expectedStreamLbls, expectedStucturedMetadataLbls, expectedParsedLbls)
 	assertLabelResult(t, expected, b.LabelsResult())
 	// cached.
 	assertLabelResult(t, expected, b.LabelsResult())
@@ -250,11 +244,7 @@ func TestLabelsBuilder_Set(t *testing.T) {
 	expectedStucturedMetadataLbls := labels.FromStrings("stzz", "stvzz")
 	expectedParsedLbls := labels.FromStrings("toreplace", "buzz")
 
-	expected := make(labels.Labels, 0, len(expectedStreamLbls)+len(expectedStucturedMetadataLbls)+len(expectedParsedLbls))
-	expected = append(expected, expectedStreamLbls...)
-	expected = append(expected, expectedStucturedMetadataLbls...)
-	expected = append(expected, expectedParsedLbls...)
-	expected = labels.New(expected...)
+	expected := mergeLabels(expectedStreamLbls, expectedStucturedMetadataLbls, expectedParsedLbls)
 
 	actual := b.LabelsResult()
 	assertLabelResult(t, expected, actual)
@@ -272,11 +262,7 @@ func TestLabelsBuilder_Set(t *testing.T) {
 	expectedStucturedMetadataLbls = labels.FromStrings("stzz", "stvzz")
 	expectedParsedLbls = labels.FromStrings("toreplace", "buzz")
 
-	expected = make(labels.Labels, 0, len(expectedStreamLbls)+len(expectedStucturedMetadataLbls)+len(expectedParsedLbls))
-	expected = append(expected, expectedStreamLbls...)
-	expected = append(expected, expectedStucturedMetadataLbls...)
-	expected = append(expected, expectedParsedLbls...)
-	expected = labels.New(expected...)
+	expected = mergeLabels(expectedStreamLbls, expectedStucturedMetadataLbls, expectedParsedLbls)
 
 	actual = b.LabelsResult()
 	assertLabelResult(t, expected, actual)
@@ -293,11 +279,7 @@ func TestLabelsBuilder_Set(t *testing.T) {
 	expectedStucturedMetadataLbls = labels.FromStrings("toreplace", "muzz")
 	expectedParsedLbls = labels.FromStrings("stzz", "stvzz")
 
-	expected = make(labels.Labels, 0, len(expectedStreamLbls)+len(expectedStucturedMetadataLbls)+len(expectedParsedLbls))
-	expected = append(expected, expectedStreamLbls...)
-	expected = append(expected, expectedStucturedMetadataLbls...)
-	expected = append(expected, expectedParsedLbls...)
-	expected = labels.New(expected...)
+	expected = mergeLabels(expectedStreamLbls, expectedStucturedMetadataLbls, expectedParsedLbls)
 
 	actual = b.LabelsResult()
 	assertLabelResult(t, expected, actual)
@@ -315,11 +297,7 @@ func TestLabelsBuilder_Set(t *testing.T) {
 	expectedStucturedMetadataLbls = labels.FromStrings("stzz", "stvzzz")
 	expectedParsedLbls = labels.FromStrings("toreplace", "puzz")
 
-	expected = make(labels.Labels, 0, len(expectedStreamLbls)+len(expectedStucturedMetadataLbls)+len(expectedParsedLbls))
-	expected = append(expected, expectedStreamLbls...)
-	expected = append(expected, expectedStucturedMetadataLbls...)
-	expected = append(expected, expectedParsedLbls...)
-	expected = labels.New(expected...)
+	expected = mergeLabels(expectedStreamLbls, expectedStucturedMetadataLbls, expectedParsedLbls)
 
 	actual = b.LabelsResult()
 	assertLabelResult(t, expected, actual)
@@ -336,11 +314,7 @@ func TestLabelsBuilder_Set(t *testing.T) {
 	expectedStucturedMetadataLbls = labels.FromStrings("toreplace", "muzz")
 	expectedParsedLbls = labels.FromStrings("stzz", "stvzzz")
 
-	expected = make(labels.Labels, 0, len(expectedStreamLbls)+len(expectedStucturedMetadataLbls)+len(expectedParsedLbls))
-	expected = append(expected, expectedStreamLbls...)
-	expected = append(expected, expectedStucturedMetadataLbls...)
-	expected = append(expected, expectedParsedLbls...)
-	expected = labels.New(expected...)
+	expected = mergeLabels(expectedStreamLbls, expectedStucturedMetadataLbls, expectedParsedLbls)
 
 	actual = b.LabelsResult()
 	assertLabelResult(t, expected, actual)
@@ -357,31 +331,37 @@ func TestLabelsBuilder_UnsortedLabels(t *testing.T) {
 	}
 	lbs := labels.FromStrings(strs...)
 	b := NewBaseLabelsBuilder().ForLabels(lbs, lbs.Hash())
-	b.add[StructuredMetadataLabel] = labels.FromStrings("toreplace", "buzz", "fzz", "bzz")
-	b.add[ParsedLabel] = labels.FromStrings("pzz", "pvzz")
-	expected := labels.FromStrings("cluster", "us-central1", "namespace", "loki", "fzz", "bzz", "toreplace", "buzz", "pzz", "pvzz")
+	b.add[StructuredMetadataLabel] = []labels.Label{{"toreplace", "buzz"}, {"fzz", "bzz"}}
+	b.add[ParsedLabel] = []labels.Label{{"pzz", "pvzz"}}
+	expected := []labels.Label{{"cluster", "us-central1"}, {"namespace", "loki"}, {"fzz", "bzz"}, {"toreplace", "buzz"}, {"pzz", "pvzz"}}
 	actual := b.UnsortedLabels(nil)
 	require.ElementsMatch(t, expected, actual)
 
 	b.Reset()
-	b.add[StructuredMetadataLabel] = labels.FromStrings("fzz", "bzz")
-	b.add[ParsedLabel] = labels.FromStrings("toreplace", "buzz", "pzz", "pvzz")
-	expected = labels.FromStrings("cluster", "us-central1", "namespace", "loki", "fzz", "bzz", "toreplace", "buzz", "pzz", "pvzz")
+	b.add[StructuredMetadataLabel] = []labels.Label{{"fzz", "bzz"}}
+	b.add[ParsedLabel] = []labels.Label{{"toreplace", "buzz"}, {"pzz", "pvzz"}}
+	expected = []labels.Label{{"cluster", "us-central1"}, {"namespace", "loki"}, {"fzz", "bzz"}, {"toreplace", "buzz"}, {"pzz", "pvzz"}}
 	actual = b.UnsortedLabels(nil)
-	sort.Sort(expected)
-	sort.Sort(actual)
+	sortLabelSlice(expected)
+	sortLabelSlice(actual)
 	assert.Equal(t, expected, actual)
 
 	b.Reset()
-	b.add[StructuredMetadataLabel] = labels.FromStrings("fzz", "bzz", "toreplacezz", "test")
-	b.add[ParsedLabel] = labels.FromStrings("toreplacezz", "buzz", "pzz", "pvzz")
-	expected = labels.FromStrings("cluster", "us-central1", "namespace", "loki", "fzz", "bzz", "toreplace", "fuzz", "pzz", "pvzz", "toreplacezz", "buzz")
+	b.add[StructuredMetadataLabel] = []labels.Label{{"fzz", "bzz"}, {"toreplacezz", "test"}}
+	b.add[ParsedLabel] = []labels.Label{{"toreplacezz", "buzz"}, {"pzz", "pvzz"}}
+	expected = []labels.Label{{"cluster", "us-central1"}, {"namespace", "loki"}, {"fzz", "bzz"}, {"toreplace", "fuzz"}, {"pzz", "pvzz"}, {"toreplacezz", "buzz"}}
 	actual = b.UnsortedLabels(nil)
-	sort.Sort(expected)
-	sort.Sort(actual)
+	sortLabelSlice(expected)
+	sortLabelSlice(actual)
 	assert.Equal(t, expected, actual)
 }
 
+func sortLabelSlice(l []labels.Label) {
+	slices.SortFunc(l, func(a, b labels.Label) int {
+		return strings.Compare(a.Name, b.Name)
+	})
+}
+
 func TestLabelsBuilder_GroupedLabelsResult(t *testing.T) {
 	strs := []string{"namespace", "loki",
 		"job", "us-central1/loki",
@@ -466,6 +446,20 @@ func assertLabelResult(t *testing.T, lbs labels.Labels, res LabelsResult) {
 	)
 }
 
+func mergeLabels(streamLabels, structuredMetadataLabels, parsedLabels labels.Labels) labels.Labels {
+	builder := labels.NewBuilder(streamLabels)
+
+	structuredMetadataLabels.Range(func(l labels.Label) {
+		builder.Set(l.Name, l.Value)
+	})
+
+	parsedLabels.Range(func(l labels.Label) {
+		builder.Set(l.Name, l.Value)
+	})
+
+	return builder.Labels()
+}
+
 // benchmark streamLineSampleExtractor.Process method
 func BenchmarkStreamLineSampleExtractor_Process(b *testing.B) {
 	// Setup some test data
@@ -477,12 +471,12 @@ func BenchmarkStreamLineSampleExtractor_Process(b *testing.B) {
 		"stream", "stdout",
 	)
 
-	structuredMeta := []labels.Label{
-		{Name: "level", Value: "info"},
-		{Name: "caller", Value: "http.go:42"},
-		{Name: "user", Value: "john"},
-		{Name: "trace_id", Value: "abc123"},
-	}
+	structuredMeta := labels.FromStrings(
+		"level", "info",
+		"caller", "http.go:42",
+		"user", "john",
+		"trace_id", "abc123",
+	)
 
 	testLine := []byte(`{"timestamp":"2024-01-01T00:00:00Z","level":"info","message":"test message","duration_ms":150}`)
 
@@ -500,7 +494,7 @@ func BenchmarkStreamLineSampleExtractor_Process(b *testing.B) {
 	b.ResetTimer()
 
 	for i := 0; i < b.N; i++ {
-		_, _ = streamEx.Process(time.Now().UnixNano(), testLine, structuredMeta...)
+		_, _ = streamEx.Process(time.Now().UnixNano(), testLine, structuredMeta)
 	}
 }
 

pkg/logql/log/metrics_extraction.go

@@ -35,8 +35,8 @@ type SampleExtractor interface {
 // A StreamSampleExtractor never mutates the received line.
 type StreamSampleExtractor interface {
 	BaseLabels() LabelsResult
-	Process(ts int64, line []byte, structuredMetadata ...labels.Label) ([]ExtractedSample, bool)
-	ProcessString(ts int64, line string, structuredMetadata ...labels.Label) ([]ExtractedSample, bool)
+	Process(ts int64, line []byte, structuredMetadata labels.Labels) ([]ExtractedSample, bool)
+	ProcessString(ts int64, line string, structuredMetadata labels.Labels) ([]ExtractedSample, bool)
 	ReferencedStructuredMetadata() bool
 }
 
@@ -99,7 +99,7 @@ func (l *streamLineSampleExtractor) ReferencedStructuredMetadata() bool {
 	return l.builder.referencedStructuredMetadata
 }
 
-func (l *streamLineSampleExtractor) Process(ts int64, line []byte, structuredMetadata ...labels.Label) ([]ExtractedSample, bool) {
+func (l *streamLineSampleExtractor) Process(ts int64, line []byte, structuredMetadata labels.Labels) ([]ExtractedSample, bool) {
 	l.builder.Reset()
 	l.builder.Add(StructuredMetadataLabel, structuredMetadata)
 
@@ -120,9 +120,9 @@ func (l *streamLineSampleExtractor) Process(ts int64, line []byte, structuredMet
 	return []ExtractedSample{{Value: value, Labels: labels}}, true
 }
 
-func (l *streamLineSampleExtractor) ProcessString(ts int64, line string, structuredMetadata ...labels.Label) ([]ExtractedSample, bool) {
+func (l *streamLineSampleExtractor) ProcessString(ts int64, line string, structuredMetadata labels.Labels) ([]ExtractedSample, bool) {
 	// unsafe get bytes since we have the guarantee that the line won't be mutated.
-	return l.Process(ts, unsafeGetBytes(line), structuredMetadata...)
+	return l.Process(ts, unsafeGetBytes(line), structuredMetadata)
 }
 
 func (l *streamLineSampleExtractor) BaseLabels() LabelsResult { return l.builder.currentResult }
@@ -199,7 +199,7 @@ func (l *labelSampleExtractor) ForStream(labels labels.Labels) StreamSampleExtra
 	return res
 }
 
-func (l *streamLabelSampleExtractor) Process(ts int64, line []byte, structuredMetadata ...labels.Label) ([]ExtractedSample, bool) {
+func (l *streamLabelSampleExtractor) Process(ts int64, line []byte, structuredMetadata labels.Labels) ([]ExtractedSample, bool) {
 	// Apply the pipeline first.
 	l.builder.Reset()
 	l.builder.Add(StructuredMetadataLabel, structuredMetadata)
@@ -230,9 +230,9 @@ func (l *streamLabelSampleExtractor) Process(ts int64, line []byte, structuredMe
 	return []ExtractedSample{{Value: v, Labels: l.builder.GroupedLabels()}}, true
 }
 
-func (l *streamLabelSampleExtractor) ProcessString(ts int64, line string, structuredMetadata ...labels.Label) ([]ExtractedSample, bool) {
+func (l *streamLabelSampleExtractor) ProcessString(ts int64, line string, structuredMetadata labels.Labels) ([]ExtractedSample, bool) {
 	// unsafe get bytes since we have the guarantee that the line won't be mutated.
-	return l.Process(ts, unsafeGetBytes(line), structuredMetadata...)
+	return l.Process(ts, unsafeGetBytes(line), structuredMetadata)
 }
 
 func (l *streamLabelSampleExtractor) BaseLabels() LabelsResult { return l.builder.currentResult }
@@ -283,7 +283,7 @@ func (sp *filteringStreamExtractor) BaseLabels() LabelsResult {
 	return sp.extractor.BaseLabels()
 }
 
-func (sp *filteringStreamExtractor) Process(ts int64, line []byte, structuredMetadata ...labels.Label) ([]ExtractedSample, bool) {
+func (sp *filteringStreamExtractor) Process(ts int64, line []byte, structuredMetadata labels.Labels) ([]ExtractedSample, bool) {
 	for _, filter := range sp.filters {
 		if ts < filter.start || ts > filter.end {
 			continue
@@ -295,10 +295,10 @@ func (sp *filteringStreamExtractor) Process(ts int64, line []byte, structuredMet
 		}
 	}
 
-	return sp.extractor.Process(ts, line, structuredMetadata...)
+	return sp.extractor.Process(ts, line, structuredMetadata)
 }
 
-func (sp *filteringStreamExtractor) ProcessString(ts int64, line string, structuredMetadata ...labels.Label) ([]ExtractedSample, bool) {
+func (sp *filteringStreamExtractor) ProcessString(ts int64, line string, structuredMetadata labels.Labels) ([]ExtractedSample, bool) {
 	for _, filter := range sp.filters {
 		if ts < filter.start || ts > filter.end {
 			continue
@@ -310,7 +310,7 @@ func (sp *filteringStreamExtractor) ProcessString(ts int64, line string, structu
 		}
 	}
 
-	return sp.extractor.ProcessString(ts, line, labels.EmptyLabels()...)
+	return sp.extractor.ProcessString(ts, line, structuredMetadata)
 }
 
 func convertFloat(v string) (float64, error) {

pkg/logql/log/metrics_extraction_test.go

@@ -251,7 +251,7 @@ func Test_labelSampleExtractor_Extract(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			samples, ok := tt.ex.ForStream(tt.in).Process(0, []byte(tt.line), tt.structuredMetadata...)
+			samples, ok := tt.ex.ForStream(tt.in).Process(0, []byte(tt.line), tt.structuredMetadata)
 			require.Equal(t, tt.wantOk, ok)
 			if ok {
 				require.Len(t, samples, 1, "Expected exactly one sample")
@@ -259,7 +259,7 @@ func Test_labelSampleExtractor_Extract(t *testing.T) {
 				require.Equal(t, tt.wantLbs, samples[0].Labels.Labels())
 			}
 
-			samples, ok = tt.ex.ForStream(tt.in).ProcessString(0, tt.line, tt.structuredMetadata...)
+			samples, ok = tt.ex.ForStream(tt.in).ProcessString(0, tt.line, tt.structuredMetadata)
 			require.Equal(t, tt.wantOk, ok)
 			if ok {
 				require.Len(t, samples, 1, "Expected exactly one sample")
@@ -273,7 +273,7 @@ func Test_labelSampleExtractor_Extract(t *testing.T) {
 func Test_Extract_ExpectedLabels(t *testing.T) {
 	ex := mustSampleExtractor(LabelExtractorWithStages("duration", ConvertDuration, []string{"foo"}, false, false, []Stage{NewJSONParser(false)}, NoopStage))
 
-	samples, ok := ex.ForStream(labels.FromStrings("bar", "foo")).ProcessString(0, `{"duration":"20ms","foo":"json"}`)
+	samples, ok := ex.ForStream(labels.FromStrings("bar", "foo")).ProcessString(0, `{"duration":"20ms","foo":"json"}`, labels.EmptyLabels())
 	require.True(t, ok)
 	require.Len(t, samples, 1, "Expected exactly one sample")
 	require.Equal(t, (20 * time.Millisecond).Seconds(), samples[0].Value)
@@ -325,7 +325,7 @@ func TestLabelExtractorWithStages(t *testing.T) {
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
 			for _, line := range tc.checkLines {
-				samples, ok := tc.extractor.ForStream(labels.FromStrings("bar", "foo")).ProcessString(0, line.logLine)
+				samples, ok := tc.extractor.ForStream(labels.FromStrings("bar", "foo")).ProcessString(0, line.logLine, labels.EmptyLabels())
 				skipped := !ok
 				assert.Equal(t, line.skip, skipped, "line", line.logLine)
 				if !skipped {
@@ -360,13 +360,13 @@ func TestNewLineSampleExtractor(t *testing.T) {
 	)
 
 	sse := se.ForStream(lbs)
-	samples, ok := sse.Process(0, []byte(`foo`))
+	samples, ok := sse.Process(0, []byte(`foo`), labels.EmptyLabels())
 	require.True(t, ok)
 	require.Len(t, samples, 1, "Expected exactly one sample")
 	require.Equal(t, 1., samples[0].Value)
 	assertLabelResult(t, lbs, samples[0].Labels)
 
-	samples, ok = sse.ProcessString(0, `foo`)
+	samples, ok = sse.ProcessString(0, `foo`, labels.EmptyLabels())
 	require.True(t, ok)
 	require.Len(t, samples, 1, "Expected exactly one sample")
 	require.Equal(t, 1., samples[0].Value)
@@ -377,21 +377,21 @@ func TestNewLineSampleExtractor(t *testing.T) {
 	require.NoError(t, err)
 
 	sse = se.ForStream(lbs)
-	samples, ok = sse.Process(0, []byte(`foo`))
+	samples, ok = sse.Process(0, []byte(`foo`), labels.EmptyLabels())
 	require.True(t, ok)
 	require.Len(t, samples, 1, "Expected exactly one sample")
 	require.Equal(t, 3., samples[0].Value)
 	assertLabelResult(t, labels.FromStrings("namespace", "dev"), samples[0].Labels)
 
 	sse = se.ForStream(lbs)
-	_, ok = sse.Process(0, []byte(`nope`))
+	_, ok = sse.Process(0, []byte(`nope`), labels.EmptyLabels())
 	require.False(t, ok)
 }
 
 func TestNewLineSampleExtractorWithStructuredMetadata(t *testing.T) {
 	lbs := labels.FromStrings("foo", "bar")
 	structuredMetadata := labels.FromStrings("user", "bob")
-	expectedLabelsResults := append(lbs, structuredMetadata...)
+	expectedLabelsResults := appendLabels(lbs, structuredMetadata)
 	se, err := NewLineSampleExtractor(CountExtractor, []Stage{
 		NewStringLabelFilter(labels.MustNewMatcher(labels.MatchEqual, "foo", "bar")),
 		NewStringLabelFilter(labels.MustNewMatcher(labels.MatchEqual, "user", "bob")),
@@ -399,34 +399,28 @@ func TestNewLineSampleExtractorWithStructuredMetadata(t *testing.T) {
 	require.NoError(t, err)
 
 	sse := se.ForStream(lbs)
-	samples, ok := sse.Process(0, []byte(`foo`), structuredMetadata...)
+	samples, ok := sse.Process(0, []byte(`foo`), structuredMetadata)
 	require.True(t, ok)
 	require.Len(t, samples, 1, "Expected exactly one sample")
 	require.Equal(t, 1., samples[0].Value)
 	assertLabelResult(t, expectedLabelsResults, samples[0].Labels)
 
-	samples, ok = sse.ProcessString(0, `foo`, structuredMetadata...)
+	samples, ok = sse.ProcessString(0, `foo`, structuredMetadata)
 	require.True(t, ok)
 	require.Len(t, samples, 1, "Expected exactly one sample")
 	require.Equal(t, 1., samples[0].Value)
 	assertLabelResult(t, expectedLabelsResults, samples[0].Labels)
 
 	// test duplicated structured metadata with stream labels
-	expectedLabelsResults = append(lbs, labels.Label{
-		Name: "foo_extracted", Value: "baz",
-	})
-	expectedLabelsResults = append(expectedLabelsResults, structuredMetadata...)
-	samples, ok = sse.Process(0, []byte(`foo`), append(structuredMetadata, labels.Label{
-		Name: "foo", Value: "baz",
-	})...)
+	expectedLabelsResults = appendLabel(lbs, "foo_extracted", "baz")
+	expectedLabelsResults = appendLabels(expectedLabelsResults, structuredMetadata)
+	samples, ok = sse.Process(0, []byte(`foo`), appendLabel(structuredMetadata, "foo", "baz"))
 	require.True(t, ok)
 	require.Len(t, samples, 1, "Expected exactly one sample")
 	require.Equal(t, 1., samples[0].Value)
 	assertLabelResult(t, expectedLabelsResults, samples[0].Labels)
 
-	samples, ok = sse.ProcessString(0, `foo`, append(structuredMetadata, labels.Label{
-		Name: "foo", Value: "baz",
-	})...)
+	samples, ok = sse.ProcessString(0, `foo`, appendLabel(structuredMetadata, "foo", "baz"))
 	require.True(t, ok)
 	require.Len(t, samples, 1, "Expected exactly one sample")
 	require.Equal(t, 1., samples[0].Value)
@@ -440,21 +434,27 @@ func TestNewLineSampleExtractorWithStructuredMetadata(t *testing.T) {
 	require.NoError(t, err)
 
 	sse = se.ForStream(lbs)
-	samples, ok = sse.Process(0, []byte(`foo`), structuredMetadata...)
+	samples, ok = sse.Process(0, []byte(`foo`), structuredMetadata)
 	require.True(t, ok)
 	require.Len(t, samples, 1, "Expected exactly one sample")
 	require.Equal(t, 3., samples[0].Value)
 	assertLabelResult(t, labels.FromStrings("foo", "bar"), samples[0].Labels)
 
 	sse = se.ForStream(lbs)
-	_, ok = sse.Process(0, []byte(`nope`))
+	_, ok = sse.Process(0, []byte(`nope`), labels.EmptyLabels())
 	require.False(t, ok)
 }
 
+func appendLabel(l labels.Labels, name, value string) labels.Labels {
+	b := labels.NewBuilder(l)
+	b.Set(name, value)
+	return b.Labels()
+}
+
 func TestFilteringSampleExtractor(t *testing.T) {
 	se := NewFilteringSampleExtractor([]PipelineFilter{
-		newPipelineFilter(2, 4, labels.FromStrings("foo", "bar", "bar", "baz"), nil, "e"),
-		newPipelineFilter(3, 5, labels.FromStrings("baz", "foo"), nil, "e"),
+		newPipelineFilter(2, 4, labels.FromStrings("foo", "bar", "bar", "baz"), labels.EmptyLabels(), "e"),
+		newPipelineFilter(3, 5, labels.FromStrings("baz", "foo"), labels.EmptyLabels(), "e"),
 		newPipelineFilter(3, 5, labels.FromStrings("foo", "baz"), labels.FromStrings("user", "bob"), "e"),
 	}, newStubExtractor())
 
@@ -466,23 +466,23 @@ func TestFilteringSampleExtractor(t *testing.T) {
 		structuredMetadata labels.Labels
 		ok                 bool
 	}{
-		{"it is after the timerange", 6, "line", labels.FromStrings("baz", "foo"), nil, true},
-		{"it is before the timerange", 1, "line", labels.FromStrings("baz", "foo"), nil, true},
-		{"it doesn't match the filter", 3, "all good", labels.FromStrings("baz", "foo"), nil, true},
-		{"it doesn't match all the selectors", 3, "line", labels.FromStrings("foo", "bar"), nil, true},
-		{"it doesn't match any selectors", 3, "line", labels.FromStrings("beep", "boop"), nil, true},
-		{"it matches all selectors", 3, "line", labels.FromStrings("foo", "bar", "bar", "baz"), nil, false},
+		{"it is after the timerange", 6, "line", labels.FromStrings("baz", "foo"), labels.EmptyLabels(), true},
+		{"it is before the timerange", 1, "line", labels.FromStrings("baz", "foo"), labels.EmptyLabels(), true},
+		{"it doesn't match the filter", 3, "all good", labels.FromStrings("baz", "foo"), labels.EmptyLabels(), true},
+		{"it doesn't match all the selectors", 3, "line", labels.FromStrings("foo", "bar"), labels.EmptyLabels(), true},
+		{"it doesn't match any selectors", 3, "line", labels.FromStrings("beep", "boop"), labels.EmptyLabels(), true},
+		{"it matches all selectors", 3, "line", labels.FromStrings("foo", "bar", "bar", "baz"), labels.EmptyLabels(), false},
 		{"it doesn't match all structured metadata", 3, "line", labels.FromStrings("foo", "baz"), labels.FromStrings("user", "alice"), true},
 		{"it matches all structured metadata", 3, "line", labels.FromStrings("foo", "baz"), labels.FromStrings("user", "bob"), false},
-		{"it tries all the filters", 5, "line", labels.FromStrings("baz", "foo"), nil, false},
+		{"it tries all the filters", 5, "line", labels.FromStrings("baz", "foo"), labels.EmptyLabels(), false},
 	}
 
 	for _, test := range tt {
 		t.Run(test.name, func(t *testing.T) {
-			_, ok := se.ForStream(test.labels).Process(test.ts, []byte(test.line), test.structuredMetadata...)
+			_, ok := se.ForStream(test.labels).Process(test.ts, []byte(test.line), test.structuredMetadata)
 			require.Equal(t, test.ok, ok)
 
-			_, ok = se.ForStream(test.labels).ProcessString(test.ts, test.line, test.structuredMetadata...)
+			_, ok = se.ForStream(test.labels).ProcessString(test.ts, test.line, test.structuredMetadata)
 			require.Equal(t, test.ok, ok)
 		})
 	}
@@ -514,7 +514,7 @@ func (p *stubStreamExtractor) BaseLabels() LabelsResult {
 func (p *stubStreamExtractor) Process(
 	_ int64,
 	_ []byte,
-	structuredMetadata ...labels.Label,
+	structuredMetadata labels.Labels,
 ) ([]ExtractedSample, bool) {
 	builder := NewBaseLabelsBuilder().ForLabels(labels.FromStrings("foo", "bar"), 0)
 	builder.Add(StructuredMetadataLabel, structuredMetadata)
@@ -527,7 +527,7 @@ func (p *stubStreamExtractor) Process(
 func (p *stubStreamExtractor) ProcessString(
 	_ int64,
 	_ string,
-	structuredMetadata ...labels.Label,
+	structuredMetadata labels.Labels,
 ) ([]ExtractedSample, bool) {
 	builder := NewBaseLabelsBuilder().ForLabels(labels.FromStrings("foo", "bar"), 0)
 	builder.Add(StructuredMetadataLabel, structuredMetadata)

pkg/logql/log/parser_hints_test.go

@@ -234,7 +234,7 @@ func Test_ParserHints(t *testing.T) {
 			require.NoError(t, err)
 
 			for i, ex := range exs {
-				res, ok := ex.ForStream(lbs).Process(0, append([]byte{}, tt.line...))
+				res, ok := ex.ForStream(lbs).Process(0, append([]byte{}, tt.line...), labels.EmptyLabels())
 				require.Equal(t, tt.expectOk, ok)
 
 				for _, sample := range res {

pkg/logql/log/parser_test.go

@@ -2,7 +2,6 @@ package log
 
 import (
 	"fmt"
-	"sort"
 	"testing"
 
 	"github.com/grafana/loki/v3/pkg/logqlmodel"
@@ -238,7 +237,7 @@ func TestKeyShortCircuit(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			_, result = tt.p.Process(0, tt.line, lbs)
 
-			require.Len(t, lbs.labels(), 1)
+			require.Equal(t, 1, lbs.LabelsResult().Labels().Len())
 			require.False(t, result)
 		})
 	}
@@ -278,7 +277,7 @@ func TestLabelShortCircuit(t *testing.T) {
 		t.Run(tt.name, func(t *testing.T) {
 			_, result = tt.p.Process(0, tt.line, lbs)
 
-			require.Len(t, lbs.labels(), 1)
+			require.Equal(t, 1, lbs.LabelsResult().Labels().Len())
 			name, category, ok := lbs.GetWithCategory("name")
 			require.True(t, ok)
 			require.Equal(t, ParsedLabel, category)
@@ -1075,7 +1074,7 @@ func TestLogfmtParser_parse(t *testing.T) {
 			[]byte(`buzz=foo bar=<EFBFBD>f`),
 			labels.EmptyLabels(),
 			labels.FromStrings("bar", " f", "buzz", "foo"),
-			nil,
+			labels.EmptyLabels(),
 			NoParserHints(),
 		},
 		{
@@ -1084,7 +1083,7 @@ func TestLogfmtParser_parse(t *testing.T) {
 			labels.FromStrings("foo", "bar"),
 			labels.FromStrings("foo", "bar",
 				"bar", "foo"),
-			nil,
+			labels.EmptyLabels(),
 			NoParserHints(),
 		},
 		{
@@ -1094,7 +1093,7 @@ func TestLogfmtParser_parse(t *testing.T) {
 			labels.FromStrings("foo", "bar",
 				"foobar", "foo bar",
 			),
-			nil,
+			labels.EmptyLabels(),
 			NoParserHints(),
 		},
 		{
@@ -1104,7 +1103,7 @@ func TestLogfmtParser_parse(t *testing.T) {
 			labels.FromStrings("a", "b",
 				"foobar", "foo\nbar\tbaz",
 			),
-			nil,
+			labels.EmptyLabels(),
 			NoParserHints(),
 		},
 		{
@@ -1114,7 +1113,7 @@ func TestLogfmtParser_parse(t *testing.T) {
 			labels.FromStrings("a", "b",
 				"foobar", "foo\nbar\tbaz",
 			),
-			nil,
+			labels.EmptyLabels(),
 			NoParserHints(),
 		},
 		{
@@ -1124,7 +1123,7 @@ func TestLogfmtParser_parse(t *testing.T) {
 			labels.FromStrings("a", "b",
 				"foobar", `foo ba\r baz`,
 			),
-			nil,
+			labels.EmptyLabels(),
 			NoParserHints(),
 		},
 		{
@@ -1134,7 +1133,7 @@ func TestLogfmtParser_parse(t *testing.T) {
 			labels.FromStrings("a", "b",
 				"foobar", "foo bar\nb\\az",
 			),
-			nil,
+			labels.EmptyLabels(),
 			NoParserHints(),
 		},
 		{
@@ -1145,7 +1144,7 @@ func TestLogfmtParser_parse(t *testing.T) {
 				"foobar", "foo bar",
 				"latency", "10ms",
 			),
-			nil,
+			labels.EmptyLabels(),
 			NoParserHints(),
 		},
 		{
@@ -1155,7 +1154,7 @@ func TestLogfmtParser_parse(t *testing.T) {
 			labels.FromStrings("foo", "bar",
 				"foobar", "foo bar",
 			),
-			nil,
+			labels.EmptyLabels(),
 			NoParserHints(),
 		},
 		{
@@ -1166,7 +1165,7 @@ func TestLogfmtParser_parse(t *testing.T) {
 				"foo_extracted", "foo bar",
 				"foobar", "10ms",
 			),
-			nil,
+			labels.EmptyLabels(),
 			NoParserHints(),
 		},
 		{
@@ -1178,7 +1177,7 @@ func TestLogfmtParser_parse(t *testing.T) {
 				"foo_bar", "10ms",
 				"test_dash", "foo",
 			),
-			nil,
+			labels.EmptyLabels(),
 			NoParserHints(),
 		},
 		{
@@ -1186,7 +1185,7 @@ func TestLogfmtParser_parse(t *testing.T) {
 			nil,
 			labels.FromStrings("foo", "bar"),
 			labels.FromStrings("foo", "bar"),
-			nil,
+			labels.EmptyLabels(),
 			NoParserHints(),
 		},
 		{
@@ -1268,10 +1267,9 @@ func TestLogfmtParser_parse(t *testing.T) {
 				_, _ = p.Process(0, tt.line, b)
 
 				want := tt.want
-				if tt.wantStrict != nil {
+				if !tt.wantStrict.IsEmpty() {
 					want = tt.wantStrict
 				}
-				sort.Sort(want)
 				require.Equal(t, want, b.LabelsResult().Labels())
 			})
 		}
@@ -1338,7 +1336,6 @@ func TestLogfmtParser_keepEmpty(t *testing.T) {
 					_, _ = p.Process(0, tt.line, b)
 
 					want := tt.want
-					sort.Sort(want)
 					require.Equal(t, want, b.LabelsResult().Labels())
 				})
 			}

pkg/logql/log/pipeline_test.go

@@ -29,7 +29,7 @@ func TestNoopPipeline(t *testing.T) {
 	require.Equal(t, true, matches)
 
 	structuredMetadata := labels.FromStrings("y", "1", "z", "2")
-	expectedLabelsResults := append(lbs, structuredMetadata...)
+	expectedLabelsResults := appendLabels(lbs, structuredMetadata)
 	l, lbr, matches = pipeline.ForStream(lbs).Process(0, []byte(""), structuredMetadata)
 	require.Equal(t, []byte(""), l)
 	require.Equal(t, NewLabelsResult(expectedLabelsResults.String(), expectedLabelsResults.Hash(), lbs, structuredMetadata, labels.EmptyLabels()), lbr)
@@ -91,8 +91,8 @@ func TestPipeline(t *testing.T) {
 
 	// Reset caches
 	p.baseBuilder.del = []string{"foo", "bar"}
-	p.baseBuilder.add = [numValidCategories]labels.Labels{
-		ParsedLabel: labels.FromStrings("baz", "blip"),
+	p.baseBuilder.add = [numValidCategories][]labels.Label{
+		ParsedLabel: {{"baz", "blip"}},
 	}
 
 	p.Reset()
@@ -106,7 +106,7 @@ func TestPipeline(t *testing.T) {
 func TestPipelineWithStructuredMetadata(t *testing.T) {
 	lbs := labels.FromStrings("foo", "bar")
 	structuredMetadata := labels.FromStrings("user", "bob")
-	expectedLabelsResults := append(lbs, structuredMetadata...)
+	expectedLabelsResults := appendLabels(lbs, structuredMetadata)
 	p := NewPipeline([]Stage{
 		NewStringLabelFilter(labels.MustNewMatcher(labels.MatchEqual, "foo", "bar")),
 		NewStringLabelFilter(labels.MustNewMatcher(labels.MatchEqual, "user", "bob")),
@@ -130,7 +130,7 @@ func TestPipelineWithStructuredMetadata(t *testing.T) {
 	// test duplicated structured metadata with stream labels
 	expectedNonIndexedLabels := labels.FromStrings("user", "bob", "foo_extracted", "baz")
 	expectedLabelsResults = labels.FromStrings("foo", "bar", "foo_extracted", "baz")
-	expectedLabelsResults = append(expectedLabelsResults, structuredMetadata...)
+	expectedLabelsResults = appendLabels(expectedLabelsResults, structuredMetadata)
 	l, lbr, matches = p.ForStream(lbs).Process(0, []byte("line"), labels.NewBuilder(structuredMetadata).Set("foo", "baz").Labels())
 	require.Equal(t, []byte("lbs bar bob"), l)
 	require.Equal(t, NewLabelsResult(expectedLabelsResults.String(), expectedLabelsResults.Hash(), lbs, expectedNonIndexedLabels, labels.EmptyLabels()), lbr)
@@ -167,8 +167,8 @@ func TestPipelineWithStructuredMetadata(t *testing.T) {
 
 	// Reset caches
 	p.baseBuilder.del = []string{"foo", "bar"}
-	p.baseBuilder.add = [numValidCategories]labels.Labels{
-		ParsedLabel: labels.FromStrings("baz", "blip"),
+	p.baseBuilder.add = [numValidCategories][]labels.Label{
+		ParsedLabel: {{"baz", "blip"}},
 	}
 
 	p.Reset()
@@ -179,6 +179,16 @@ func TestPipelineWithStructuredMetadata(t *testing.T) {
 	}
 }
 
+func appendLabels(base labels.Labels, l labels.Labels) labels.Labels {
+	b := labels.NewBuilder(base)
+
+	l.Range(func(l labels.Label) {
+		b.Set(l.Name, l.Value)
+	})
+
+	return b.Labels()
+}
+
 func TestFilteringPipeline(t *testing.T) {
 	tt := []struct {
 		name               string
@@ -188,22 +198,22 @@ func TestFilteringPipeline(t *testing.T) {
 		structuredMetadata labels.Labels
 		ok                 bool
 	}{
-		{"it is before the timerange", 1, "line", labels.FromStrings("baz", "foo"), nil, true},
-		{"it is after the timerange", 6, "line", labels.FromStrings("baz", "foo"), nil, true},
-		{"it doesn't match the filter", 3, "all good", labels.FromStrings("baz", "foo"), nil, true},
-		{"it doesn't match all the selectors", 3, "line", labels.FromStrings("foo", "bar"), nil, true},
-		{"it doesn't match any selectors", 3, "line", labels.FromStrings("beep", "boop"), nil, true},
-		{"it matches all selectors", 3, "line", labels.FromStrings("foo", "bar", "bar", "baz"), nil, false},
+		{"it is before the timerange", 1, "line", labels.FromStrings("baz", "foo"), labels.EmptyLabels(), true},
+		{"it is after the timerange", 6, "line", labels.FromStrings("baz", "foo"), labels.EmptyLabels(), true},
+		{"it doesn't match the filter", 3, "all good", labels.FromStrings("baz", "foo"), labels.EmptyLabels(), true},
+		{"it doesn't match all the selectors", 3, "line", labels.FromStrings("foo", "bar"), labels.EmptyLabels(), true},
+		{"it doesn't match any selectors", 3, "line", labels.FromStrings("beep", "boop"), labels.EmptyLabels(), true},
+		{"it matches all selectors", 3, "line", labels.FromStrings("foo", "bar", "bar", "baz"), labels.EmptyLabels(), false},
 		{"it doesn't match all structured metadata", 3, "line", labels.FromStrings("foo", "baz"), labels.FromStrings("user", "alice"), true},
 		{"it matches all structured metadata", 3, "line", labels.FromStrings("foo", "baz"), labels.FromStrings("user", "bob"), false},
-		{"it tries all the filters", 5, "line", labels.FromStrings("baz", "foo"), nil, false},
+		{"it tries all the filters", 5, "line", labels.FromStrings("baz", "foo"), labels.EmptyLabels(), false},
 	}
 
 	for _, test := range tt {
 		downstream := newStubPipeline()
 		p := NewFilteringPipeline([]PipelineFilter{
-			newPipelineFilter(2, 4, labels.FromStrings("foo", "bar", "bar", "baz"), nil, "e"),
-			newPipelineFilter(3, 5, labels.FromStrings("baz", "foo"), nil, "e"),
+			newPipelineFilter(2, 4, labels.FromStrings("foo", "bar", "bar", "baz"), labels.EmptyLabels(), "e"),
+			newPipelineFilter(3, 5, labels.FromStrings("baz", "foo"), labels.EmptyLabels(), "e"),
 			newPipelineFilter(3, 5, labels.FromStrings("foo", "baz"), labels.FromStrings("user", "bob"), "e"),
 		}, downstream)
 
@@ -380,8 +390,8 @@ func TestDropLabelsPipeline(t *testing.T) {
 		for i, line := range tt.lines {
 			_, finalLbs, _ := sp.Process(0, line, labels.EmptyLabels())
 			require.Equal(t, tt.wantLabels[i], finalLbs.Labels())
-			require.Nil(t, finalLbs.Stream())
-			require.Nil(t, finalLbs.StructuredMetadata())
+			require.Equal(t, labels.EmptyLabels(), finalLbs.Stream())
+			require.Equal(t, labels.EmptyLabels(), finalLbs.StructuredMetadata())
 			require.Equal(t, tt.wantLabels[i], finalLbs.Parsed())
 			require.Equal(t, tt.wantLabels[i].Hash(), finalLbs.Hash())
 		}
@@ -502,13 +512,9 @@ func TestKeepLabelsPipeline(t *testing.T) {
 				finalLine, finalLbs, _ := sp.Process(0, line, labels.EmptyLabels())
 				require.Equal(t, tt.wantLine[i], finalLine)
 				require.Equal(t, tt.wantLabels[i], finalLbs.Labels())
-				require.Nil(t, finalLbs.Stream())
-				require.Nil(t, finalLbs.StructuredMetadata())
-				if len(tt.wantLabels[i]) > 0 {
-					require.Equal(t, tt.wantLabels[i], finalLbs.Parsed())
-				} else {
-					require.Nil(t, finalLbs.Parsed())
-				}
+				require.Equal(t, labels.EmptyLabels(), finalLbs.Stream())
+				require.Equal(t, labels.EmptyLabels(), finalLbs.StructuredMetadata())
+				require.Equal(t, tt.wantLabels[i], finalLbs.Parsed())
 				require.Equal(t, tt.wantLabels[i].Hash(), finalLbs.Hash())
 				require.Equal(t, tt.wantLabels[i].String(), finalLbs.String())
 			}
@@ -615,7 +621,7 @@ func Benchmark_Pipeline(b *testing.B) {
 	b.Run("line extractor bytes", func(b *testing.B) {
 		b.ResetTimer()
 		for n := 0; n < b.N; n++ {
-			samples, ok := ex.Process(0, line)
+			samples, ok := ex.Process(0, line, labels.EmptyLabels())
 			if ok && len(samples) > 0 {
 				resSample = samples[0].Value
 				resLbs = samples[0].Labels
@@ -628,7 +634,7 @@ func Benchmark_Pipeline(b *testing.B) {
 	b.Run("line extractor string", func(b *testing.B) {
 		b.ResetTimer()
 		for n := 0; n < b.N; n++ {
-			samples, ok := ex.ProcessString(0, lineString)
+			samples, ok := ex.ProcessString(0, lineString, labels.EmptyLabels())
 			if ok && len(samples) > 0 {
 				resSample = samples[0].Value
 				resLbs = samples[0].Labels
@@ -646,7 +652,7 @@ func Benchmark_Pipeline(b *testing.B) {
 	b.Run("label extractor bytes", func(b *testing.B) {
 		b.ResetTimer()
 		for n := 0; n < b.N; n++ {
-			samples, ok := ex.Process(0, line)
+			samples, ok := ex.Process(0, line, labels.EmptyLabels())
 			if ok && len(samples) > 0 {
 				resSample = samples[0].Value
 				resLbs = samples[0].Labels
@@ -659,7 +665,7 @@ func Benchmark_Pipeline(b *testing.B) {
 	b.Run("label extractor string", func(b *testing.B) {
 		b.ResetTimer()
 		for n := 0; n < b.N; n++ {
-			samples, ok := ex.ProcessString(0, lineString)
+			samples, ok := ex.ProcessString(0, lineString, labels.EmptyLabels())
 			if ok && len(samples) > 0 {
 				resSample = samples[0].Value
 				resLbs = samples[0].Labels

pkg/logql/syntax/extractor_test.go

@@ -157,7 +157,7 @@ func Test_MultiVariantExpr_Extractors(t *testing.T) {
 				streamExtractor := extractors[0].ForStream(lbls)
 				require.NotNil(t, streamExtractor, "stream extractor should not be nil")
 
-				samples, ok := streamExtractor.Process(now.UnixNano(), []byte(tc.testLine))
+				samples, ok := streamExtractor.Process(now.UnixNano(), []byte(tc.testLine), labels.EmptyLabels())
 				require.True(t, ok)
 
 				seen := make(map[string]float64, len(samples))
@@ -176,7 +176,7 @@ func Test_MultiVariantExpr_Extractors(t *testing.T) {
 				streamExtractor = extractors[0].ForStream(lbls)
 				require.NotNil(t, streamExtractor, "multi-variant stream extractor should not be nil")
 
-				mvSamples, ok := streamExtractor.Process(now.UnixNano(), []byte(tc.testLine))
+				mvSamples, ok := streamExtractor.Process(now.UnixNano(), []byte(tc.testLine), labels.EmptyLabels())
 				require.True(t, ok)
 
 				// remove variant label
@@ -412,7 +412,7 @@ func Test_MultiVariantExpr_Extractors(t *testing.T) {
 				streamExtractor := extractors[0].ForStream(lbls)
 				require.NotNil(t, streamExtractor, "stream extractor should not be nil")
 
-				samples, ok := streamExtractor.Process(now.UnixNano(), []byte(tc.testLine))
+				samples, ok := streamExtractor.Process(now.UnixNano(), []byte(tc.testLine), labels.EmptyLabels())
 				require.True(t, ok)
 
 				expectedSamples := make(map[string]float64, len(tc.expected))

pkg/logql/syntax/parser.go

@@ -3,7 +3,6 @@ package syntax
 import (
 	"errors"
 	"fmt"
-	"sort"
 	"strings"
 	"sync"
 
@@ -272,11 +271,8 @@ func ParseLogSelector(input string, validate bool) (LogSelectorExpr, error) {
 func ParseLabels(lbs string) (labels.Labels, error) {
 	ls, err := promql_parser.ParseMetric(lbs)
 	if err != nil {
-		return nil, err
+		return labels.EmptyLabels(), err
 	}
-	// Sort labels to ensure functionally equivalent
-	// inputs map to the same output
-	sort.Sort(ls)
 
 	// Use the label builder to trim empty label values.
 	// Empty label values are equivalent to absent labels

pkg/logql/syntax/parser_test.go

@@ -3506,7 +3506,7 @@ func Benchmark_MetricPipelineCombined(b *testing.B) {
 		b.ReportAllocs()
 		b.ResetTimer()
 		for i := 0; i < b.N; i++ {
-			samples, matches = sp.Process(0, in)
+			samples, matches = sp.Process(0, in, labels.EmptyLabels())
 		}
 
 		v = samples[0].Value
@@ -3678,6 +3678,22 @@ func TestParseLabels(t *testing.T) {
 			input:  `{job="foo"}`,
 			output: labels.FromStrings("job", "foo"),
 		},
+		{
+			desc:  "multiple labels, already sorted",
+			input: `{env="a", job="foo"}`,
+			output: labels.FromStrings(
+				"env", "a",
+				"job", "foo",
+			),
+		},
+		{
+			desc:  "multiple labels, not sorted",
+			input: `{job="foo", env="a"}`,
+			output: labels.FromStrings(
+				"env", "a",
+				"job", "foo",
+			),
+		},
 		{
 			desc:   "strip empty label value",
 			input:  `{job="foo", bar=""}`,

pkg/logql/test_utils.go

@@ -148,7 +148,7 @@ func processSeries(in []logproto.Stream, ex []log.SampleExtractor) ([]logproto.S
 			exs := extractor.ForStream(mustParseLabels(stream.Labels))
 			for _, e := range stream.Entries {
 
-				if samples, ok := exs.Process(e.Timestamp.UnixNano(), []byte(e.Line)); ok {
+				if samples, ok := exs.Process(e.Timestamp.UnixNano(), []byte(e.Line), labels.EmptyLabels()); ok {
 					for _, sample := range samples {
 						lbs := sample.Labels
 						f := sample.Value

pkg/storage/lazy_chunk_test.go

@@ -52,8 +52,10 @@ func TestLazyChunkIterator(t *testing.T) {
 					Hash:   fooLabelsWithName.Hash(),
 					Entries: []logproto.Entry{
 						{
-							Timestamp: from,
-							Line:      "1",
+							Timestamp:          from,
+							Line:               "1",
+							Parsed:             logproto.EmptyLabelAdapters(),
+							StructuredMetadata: logproto.EmptyLabelAdapters(),
 						},
 					},
 				}),
@@ -63,8 +65,10 @@ func TestLazyChunkIterator(t *testing.T) {
 						Hash:   fooLabels.Hash(),
 						Entries: []logproto.Entry{
 							{
-								Timestamp: from,
-								Line:      "1",
+								Timestamp:          from,
+								Line:               "1",
+								Parsed:             logproto.EmptyLabelAdapters(),
+								StructuredMetadata: logproto.EmptyLabelAdapters(),
 							},
 						},
 					},

pkg/storage/store_test.go

@@ -1133,14 +1133,14 @@ func (p *mockStreamExtractor) BaseLabels() lokilog.LabelsResult {
 	return p.wrappedSP.BaseLabels()
 }
 
-func (p *mockStreamExtractor) Process(ts int64, line []byte, lbs ...labels.Label) ([]lokilog.ExtractedSample, bool) {
+func (p *mockStreamExtractor) Process(ts int64, line []byte, lbs labels.Labels) ([]lokilog.ExtractedSample, bool) {
 	p.called++
-	return p.wrappedSP.Process(ts, line, lbs...)
+	return p.wrappedSP.Process(ts, line, lbs)
 }
 
-func (p *mockStreamExtractor) ProcessString(ts int64, line string, lbs ...labels.Label) ([]lokilog.ExtractedSample, bool) {
+func (p *mockStreamExtractor) ProcessString(ts int64, line string, lbs labels.Labels) ([]lokilog.ExtractedSample, bool) {
 	p.called++
-	return p.wrappedSP.ProcessString(ts, line, lbs...)
+	return p.wrappedSP.ProcessString(ts, line, lbs)
 }
 
 func Test_store_GetSeries(t *testing.T) {
@@ -2041,6 +2041,7 @@ func TestQueryReferencingStructuredMetadata(t *testing.T) {
 			entry := logproto.Entry{
 				Timestamp: ts,
 				Line:      fmt.Sprintf("ts=%d level=info", ts.Unix()),
+				Parsed:    logproto.EmptyLabelAdapters(),
 			}
 
 			if withStructuredMetadata {
@@ -2054,6 +2055,8 @@ func TestQueryReferencingStructuredMetadata(t *testing.T) {
 						Value: "1",
 					},
 				}
+			} else {
+				entry.StructuredMetadata = logproto.EmptyLabelAdapters()
 			}
 			dup, err := chunkEnc.Append(&entry)
 			require.False(t, dup)
@@ -2086,6 +2089,7 @@ func TestQueryReferencingStructuredMetadata(t *testing.T) {
 			expectedEntry := logproto.Entry{
 				Timestamp: ts.Truncate(0),
 				Line:      fmt.Sprintf("ts=%d level=info", ts.Unix()),
+				Parsed:    logproto.EmptyLabelAdapters(),
 			}
 
 			if withStructuredMetadata {
@@ -2099,6 +2103,8 @@ func TestQueryReferencingStructuredMetadata(t *testing.T) {
 						Value: "1",
 					},
 				}
+			} else {
+				expectedEntry.StructuredMetadata = logproto.EmptyLabelAdapters()
 			}
 			require.Equal(t, expectedEntry, it.At())
 		}