diff --git a/lib/logstorage/pipes.go b/lib/logstorage/pipes.go
index 72adddb30..5106c1c1e 100644
--- a/lib/logstorage/pipes.go
+++ b/lib/logstorage/pipes.go
@@ -254,8 +254,8 @@ func (sp *statsPipe) newPipeProcessor(workersCount int, stopCh <-chan struct{},
 	shards := make([]statsPipeProcessorShard, workersCount)
 	for i := range shards {
 		shard := &shards[i]
+		shard.sp = sp
 		shard.m = make(map[string]*statsPipeGroup)
-		shard.funcs = sp.funcs
 		shard.stateSizeBudget = stateSizeBudgetChunk
 		maxStateSize -= stateSizeBudgetChunk
 	}
@@ -295,8 +295,8 @@ type statsPipeProcessorShard struct {
 }
 
 type statsPipeProcessorShardNopad struct {
-	m     map[string]*statsPipeGroup
-	funcs []statsFunc
+	sp *statsPipe
+	m  map[string]*statsPipeGroup
 
 	columnValues [][]string
 	keyBuf       []byte
@@ -304,11 +304,11 @@ type statsPipeProcessorShardNopad struct {
 	stateSizeBudget int
 }
 
-func (shard *statsPipeProcessorShard) getStatsPipeGroup(key []byte) *statsPipeGroup {
+func (shard *statsPipeProcessorShard) getStatsFuncProcessors(key []byte) []statsFuncProcessor {
 	spg := shard.m[string(key)]
 	if spg == nil {
-		sfps := make([]statsFuncProcessor, len(shard.funcs))
-		for i, f := range shard.funcs {
+		sfps := make([]statsFuncProcessor, len(shard.sp.funcs))
+		for i, f := range shard.sp.funcs {
 			sfp, stateSize := f.newStatsFuncProcessor()
 			sfps[i] = sfp
 			shard.stateSizeBudget -= stateSize
@@ -319,7 +319,7 @@ func (shard *statsPipeProcessorShard) getStatsPipeGroup(key []byte) *statsPipeGr
 		shard.m[string(key)] = spg
 		shard.stateSizeBudget -= len(key) + int(unsafe.Sizeof("")+unsafe.Sizeof(spg)+unsafe.Sizeof(sfps[0])*uintptr(len(sfps)))
 	}
-	return spg
+	return spg.sfps
 }
 
 type statsPipeGroup struct {
@@ -344,10 +344,10 @@ func (spp *statsPipeProcessor) writeBlock(workerID uint, timestamps []int64, col
 	}
 
 	byFields := spp.sp.byFields
-	if len(byFields) == 0 || len(byFields) == 1 && getBlockColumnIndex(columns, byFields[0]) < 0 {
+	if len(byFields) == 0 {
 		// Fast path - pass all the rows to a single group with empty key.
-		spg := shard.getStatsPipeGroup(nil)
-		for _, sfp := range spg.sfps {
+		sfps := shard.getStatsFuncProcessors(nil)
+		for _, sfp := range sfps {
 			shard.stateSizeBudget -= sfp.updateStatsForAllRows(timestamps, columns)
 		}
 		return
@@ -363,14 +363,14 @@ func (spp *statsPipeProcessor) writeBlock(workerID uint, timestamps []int64, col
 		}
 		values := columns[idx].Values
 
-		var spg *statsPipeGroup
+		var sfps []statsFuncProcessor
 		keyBuf := shard.keyBuf
 		for i := range timestamps {
 			if i <= 0 || values[i-1] != values[i] {
 				keyBuf = encoding.MarshalBytes(keyBuf[:0], bytesutil.ToUnsafeBytes(values[i]))
-				spg = shard.getStatsPipeGroup(keyBuf)
+				sfps = shard.getStatsFuncProcessors(keyBuf)
 			}
-			for _, sfp := range spg.sfps {
+			for _, sfp := range sfps {
 				shard.stateSizeBudget -= sfp.updateStatsForRow(timestamps, columns, i)
 			}
 		}
@@ -383,11 +383,11 @@ func (spp *statsPipeProcessor) writeBlock(workerID uint, timestamps []int64, col
 	shard.columnValues = appendBlockColumnValues(shard.columnValues[:0], columns, spp.sp.byFields)
 	columnValues := shard.columnValues
 
-	var spg *statsPipeGroup
+	var sfps []statsFuncProcessor
 	keyBuf := shard.keyBuf
 	for i := range timestamps {
 		// verify whether the key for 'by (...)' fields equals the previous key
-		sameValue := spg != nil
+		sameValue := sfps != nil
 		for _, values := range columnValues {
 			if values == nil {
 				continue
@@ -407,9 +407,9 @@ func (spp *statsPipeProcessor) writeBlock(workerID uint, timestamps []int64, col
 				}
 				keyBuf = encoding.MarshalBytes(keyBuf, bytesutil.ToUnsafeBytes(v))
 			}
-			spg = shard.getStatsPipeGroup(keyBuf)
+			sfps = shard.getStatsFuncProcessors(keyBuf)
 		}
-		for _, sfp := range spg.sfps {
+		for _, sfp := range sfps {
 			shard.stateSizeBudget -= sfp.updateStatsForRow(timestamps, columns, i)
 		}
 	}
@@ -451,7 +451,7 @@ func (spp *statsPipeProcessor) flush() error {
 	byFields := spp.sp.byFields
 	if len(byFields) == 0 && len(m) == 0 {
 		// Special case - zero matching rows.
-		_ = shards[0].getStatsPipeGroup(nil)
+		_ = shards[0].getStatsFuncProcessors(nil)
 		m = shards[0].m
 	}