lib/logstorage: consistently use "pHits := m[..]" pattern

Consistency improves maintainability of the code a bit.

lib/logstorage/pipe_field_names.go

@@ -103,8 +103,8 @@ func (pfp *pipeFieldNamesProcessor) writeBlock(workerID uint, br *blockResult) {
 
 	cs := br.getColumns()
 	for _, c := range cs {
-		pHits, ok := m[c.name]
-		if !ok {
+		pHits := m[c.name]
+		if pHits == nil {
 			nameCopy := strings.Clone(c.name)
 			hits := uint64(0)
 			pHits = &hits
@@ -128,8 +128,8 @@ func (pfp *pipeFieldNamesProcessor) flush() error {
 	shards = shards[1:]
 	for i := range shards {
 		for name, pHitsSrc := range shards[i].getM() {
-			pHits, ok := m[name]
-			if !ok {
+			pHits := m[name]
+			if pHits == nil {
 				m[name] = pHitsSrc
 			} else {
 				*pHits += *pHitsSrc

lib/logstorage/pipe_uniq.go

@@ -217,8 +217,8 @@ func (shard *pipeUniqProcessorShard) writeBlock(br *blockResult) bool {
 
 func (shard *pipeUniqProcessorShard) updateState(v string, hits uint64) {
 	m := shard.getM()
-	pHits, ok := m[v]
-	if !ok {
+	pHits := m[v]
+	if pHits == nil {
 		vCopy := strings.Clone(v)
 		hits := uint64(0)
 		pHits = &hits

lib/logstorage/storage_search.go

@@ -337,8 +337,8 @@ func (s *Storage) GetStreamFieldNames(ctx context.Context, tenantIDs []TenantID,
 
 	m := make(map[string]*uint64)
 	forEachStreamField(streams, func(f Field, hits uint64) {
-		pHits, ok := m[f.Name]
-		if !ok {
+		pHits := m[f.Name]
+		if pHits == nil {
 			nameCopy := strings.Clone(f.Name)
 			hitsLocal := uint64(0)
 			pHits = &hitsLocal
@@ -364,8 +364,8 @@ func (s *Storage) GetStreamFieldValues(ctx context.Context, tenantIDs []TenantID
 		if f.Name != fieldName {
 			return
 		}
-		pHits, ok := m[f.Value]
-		if !ok {
+		pHits := m[f.Value]
+		if pHits == nil {
 			valueCopy := strings.Clone(f.Value)
 			hitsLocal := uint64(0)
 			pHits = &hitsLocal