diff --git a/lib/logstorage/block_result.go b/lib/logstorage/block_result.go
index 48a529316..d73df433a 100644
--- a/lib/logstorage/block_result.go
+++ b/lib/logstorage/block_result.go
@@ -95,7 +95,7 @@ func (br *blockResult) clone() *blockResult {
 
 // initFromNeededColumns initializes br from brSrc, by copying only the given neededColumns for rows identified by set bits at bm.
 //
-// The br valid until brSrc is reset or bm is updated.
+// The br valid until brSrc or bm is updated.
 func (br *blockResult) initFromNeededColumns(brSrc *blockResult, bm *bitmap, neededColumns []string) {
 	br.reset()
 
@@ -106,6 +106,11 @@ func (br *blockResult) initFromNeededColumns(brSrc *blockResult, bm *bitmap, nee
 	})
 	br.timestamps = dstTimestamps
 
+	if len(br.timestamps) == 0 {
+		// There is no need in initializing columns for zero rows.
+		return
+	}
+
 	for _, neededColumn := range neededColumns {
 		cSrc := brSrc.getColumnByName(neededColumn)
 
@@ -1277,6 +1282,9 @@ func (br *blockResult) areSameColumns(columnNames []string) bool {
 }
 
 func (br *blockResult) getColumnByName(columnName string) *blockResultColumn {
+	if columnName == "" {
+		columnName = "_msg"
+	}
 	for _, c := range br.getColumns() {
 		if c.name == columnName {
 			return c
diff --git a/lib/logstorage/filter_phrase.go b/lib/logstorage/filter_phrase.go
index 76658c5b3..4ca15e6f7 100644
--- a/lib/logstorage/filter_phrase.go
+++ b/lib/logstorage/filter_phrase.go
@@ -32,8 +32,8 @@ func (fp *filterPhrase) String() string {
 	return quoteFieldNameIfNeeded(fp.fieldName) + quoteTokenIfNeeded(fp.phrase)
 }
 
-func (fp *filterPhrase) updateNeededFields(neededColumns fieldsSet) {
-	neededColumns.add(fp.fieldName)
+func (fp *filterPhrase) updateNeededFields(neededFields fieldsSet) {
+	neededFields.add(fp.fieldName)
 }
 
 func (fp *filterPhrase) getTokens() []string {
diff --git a/lib/logstorage/pipe_stats.go b/lib/logstorage/pipe_stats.go
index b9a211350..0a19bb65b 100644
--- a/lib/logstorage/pipe_stats.go
+++ b/lib/logstorage/pipe_stats.go
@@ -523,16 +523,16 @@ func parsePipeStats(lex *lexer) (*pipeStats, error) {
 		}
 		f.f = sf
 
-		neededFields := newFieldsSet()
-		f.f.updateNeededFields(neededFields)
-		f.neededFieldsForFunc = neededFields.getAll()
-
 		if lex.isKeyword("if") {
 			iff, err := parseIfFilter(lex)
 			if err != nil {
 				return nil, fmt.Errorf("cannot parse 'if' filter for %s: %w", sf, err)
 			}
 			f.iff = iff
+
+			neededFields := newFieldsSet()
+			iff.updateNeededFields(neededFields)
+			f.neededFieldsForFunc = neededFields.getAll()
 		}
 
 		resultName, err := parseResultName(lex)