diff --git a/lib/logstorage/filter.go b/lib/logstorage/filter.go
index ecee1de7a..93a2e6005 100644
--- a/lib/logstorage/filter.go
+++ b/lib/logstorage/filter.go
@@ -24,32 +24,6 @@ type filter interface {
 	apply(bs *blockSearch, bm *bitmap)
 }
 
-// notFilter negates the filter.
-//
-// It is expressed as `NOT f` or `!f` in LogsQL.
-type notFilter struct {
-	f filter
-}
-
-func (fn *notFilter) String() string {
-	s := fn.f.String()
-	switch fn.f.(type) {
-	case *filterAnd, *filterOr:
-		s = "(" + s + ")"
-	}
-	return "!" + s
-}
-
-func (fn *notFilter) apply(bs *blockSearch, bm *bitmap) {
-	// Minimize the number of rows to check by the filter by applying it
-	// only to the rows, which match the bm, e.g. they may change the bm result.
-	bmTmp := getBitmap(bm.bitsLen)
-	bmTmp.copyFrom(bm)
-	fn.f.apply(bs, bmTmp)
-	bm.andNot(bmTmp)
-	putBitmap(bmTmp)
-}
-
 // streamFilter is the filter for `_stream:{...}`
 type streamFilter struct {
 	// f is the filter to apply
diff --git a/lib/logstorage/filter_not.go b/lib/logstorage/filter_not.go
new file mode 100644
index 000000000..37b36f2e7
--- /dev/null
+++ b/lib/logstorage/filter_not.go
@@ -0,0 +1,27 @@
+package logstorage
+
+// filterNot negates the filter.
+//
+// It is expressed as `NOT f` or `!f` in LogsQL.
+type filterNot struct {
+	f filter
+}
+
+func (fn *filterNot) String() string {
+	s := fn.f.String()
+	switch fn.f.(type) {
+	case *filterAnd, *filterOr:
+		s = "(" + s + ")"
+	}
+	return "!" + s
+}
+
+func (fn *filterNot) apply(bs *blockSearch, bm *bitmap) {
+	// Minimize the number of rows to check by the filter by applying it
+	// only to the rows, which match the bm, e.g. they may change the bm result.
+	bmTmp := getBitmap(bm.bitsLen)
+	bmTmp.copyFrom(bm)
+	fn.f.apply(bs, bmTmp)
+	bm.andNot(bmTmp)
+	putBitmap(bmTmp)
+}
diff --git a/lib/logstorage/filter_not_test.go b/lib/logstorage/filter_not_test.go
new file mode 100644
index 000000000..722dc7f43
--- /dev/null
+++ b/lib/logstorage/filter_not_test.go
@@ -0,0 +1,75 @@
+package logstorage
+
+import (
+	"testing"
+)
+
+func TestFilterNot(t *testing.T) {
+	columns := []column{
+		{
+			name: "foo",
+			values: []string{
+				"a foo",
+				"a foobar",
+				"aa abc a",
+				"ca afdf a,foobar baz",
+				"a fddf foobarbaz",
+				"",
+				"a foobar",
+				"a kjlkjf dfff",
+				"a ТЕСТЙЦУК НГКШ ",
+				"a !!,23.(!1)",
+			},
+		},
+	}
+
+	// match
+	fn := &filterNot{
+		f: &phraseFilter{
+			fieldName: "foo",
+			phrase:    "",
+		},
+	}
+	testFilterMatchForColumns(t, columns, fn, "foo", []int{0, 1, 2, 3, 4, 6, 7, 8, 9})
+
+	fn = &filterNot{
+		f: &phraseFilter{
+			fieldName: "foo",
+			phrase:    "a",
+		},
+	}
+	testFilterMatchForColumns(t, columns, fn, "foo", []int{5})
+
+	fn = &filterNot{
+		f: &phraseFilter{
+			fieldName: "non-existing-field",
+			phrase:    "foobar",
+		},
+	}
+	testFilterMatchForColumns(t, columns, fn, "foo", []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9})
+
+	fn = &filterNot{
+		f: &prefixFilter{
+			fieldName: "non-existing-field",
+			prefix:    "",
+		},
+	}
+	testFilterMatchForColumns(t, columns, fn, "foo", []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9})
+
+	fn = &filterNot{
+		f: &prefixFilter{
+			fieldName: "foo",
+			prefix:    "",
+		},
+	}
+	testFilterMatchForColumns(t, columns, fn, "foo", []int{5})
+
+	// mismatch
+	fn = &filterNot{
+		f: &phraseFilter{
+			fieldName: "non-existing-field",
+			phrase:    "",
+		},
+	}
+	testFilterMatchForColumns(t, columns, fn, "foo", nil)
+}
diff --git a/lib/logstorage/filter_test.go b/lib/logstorage/filter_test.go
index 88df031d2..2779f5095 100644
--- a/lib/logstorage/filter_test.go
+++ b/lib/logstorage/filter_test.go
@@ -362,7 +362,7 @@ func TestComplexFilters(t *testing.T) {
 				fieldName: "foo",
 				phrase:    "foobar",
 			},
-			&notFilter{
+			&filterNot{
 				f: &phraseFilter{
 					fieldName: "foo",
 					phrase:    "baz",
@@ -391,7 +391,7 @@ func TestComplexFilters(t *testing.T) {
 				fieldName: "foo",
 				phrase:    "foobaz",
 			},
-			&notFilter{
+			&filterNot{
 				f: &phraseFilter{
 					fieldName: "foo",
 					phrase:    "baz",
@@ -420,7 +420,7 @@ func TestComplexFilters(t *testing.T) {
 				fieldName: "foo",
 				phrase:    "foobar",
 			},
-			&notFilter{
+			&filterNot{
 				f: &phraseFilter{
 					fieldName: "foo",
 					phrase:    "baz",
@@ -453,7 +453,7 @@ func TestComplexFilters(t *testing.T) {
 				fieldName: "foo",
 				phrase:    "foobar",
 			},
-			&notFilter{
+			&filterNot{
 				f: &phraseFilter{
 					fieldName: "foo",
 					phrase:    "qwert",
@@ -480,76 +480,6 @@ func TestComplexFilters(t *testing.T) {
 	testFilterMatchForColumns(t, columns, f, "foo", []int{1, 3, 6})
 }
 
-func TestNotFilter(t *testing.T) {
-	columns := []column{
-		{
-			name: "foo",
-			values: []string{
-				"a foo",
-				"a foobar",
-				"aa abc a",
-				"ca afdf a,foobar baz",
-				"a fddf foobarbaz",
-				"",
-				"a foobar",
-				"a kjlkjf dfff",
-				"a ТЕСТЙЦУК НГКШ ",
-				"a !!,23.(!1)",
-			},
-		},
-	}
-
-	// match
-	nf := &notFilter{
-		f: &phraseFilter{
-			fieldName: "foo",
-			phrase:    "",
-		},
-	}
-	testFilterMatchForColumns(t, columns, nf, "foo", []int{0, 1, 2, 3, 4, 6, 7, 8, 9})
-
-	nf = &notFilter{
-		f: &phraseFilter{
-			fieldName: "foo",
-			phrase:    "a",
-		},
-	}
-	testFilterMatchForColumns(t, columns, nf, "foo", []int{5})
-
-	nf = &notFilter{
-		f: &phraseFilter{
-			fieldName: "non-existing-field",
-			phrase:    "foobar",
-		},
-	}
-	testFilterMatchForColumns(t, columns, nf, "foo", []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9})
-
-	nf = &notFilter{
-		f: &prefixFilter{
-			fieldName: "non-existing-field",
-			prefix:    "",
-		},
-	}
-	testFilterMatchForColumns(t, columns, nf, "foo", []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9})
-
-	nf = &notFilter{
-		f: &prefixFilter{
-			fieldName: "foo",
-			prefix:    "",
-		},
-	}
-	testFilterMatchForColumns(t, columns, nf, "foo", []int{5})
-
-	// mismatch
-	nf = &notFilter{
-		f: &phraseFilter{
-			fieldName: "non-existing-field",
-			phrase:    "",
-		},
-	}
-	testFilterMatchForColumns(t, columns, nf, "foo", nil)
-}
-
 func TestTimeFilter(t *testing.T) {
 	timestamps := []int64{
 		1,
diff --git a/lib/logstorage/parser.go b/lib/logstorage/parser.go
index 5acb4ab4b..2072f33dd 100644
--- a/lib/logstorage/parser.go
+++ b/lib/logstorage/parser.go
@@ -242,17 +242,17 @@ func parseFilter(lex *lexer) (filter, error) {
 	if !lex.mustNextToken() || lex.isKeyword("|") {
 		return nil, fmt.Errorf("missing query")
 	}
-	fo, err := parseOrFilter(lex, "")
+	fo, err := parseFilterOr(lex, "")
 	if err != nil {
 		return nil, err
 	}
 	return fo, nil
 }
 
-func parseOrFilter(lex *lexer, fieldName string) (filter, error) {
+func parseFilterOr(lex *lexer, fieldName string) (filter, error) {
 	var filters []filter
 	for {
-		f, err := parseAndFilter(lex, fieldName)
+		f, err := parseFilterAnd(lex, fieldName)
 		if err != nil {
 			return nil, err
 		}
@@ -274,7 +274,7 @@ func parseOrFilter(lex *lexer, fieldName string) (filter, error) {
 	}
 }
 
-func parseAndFilter(lex *lexer, fieldName string) (filter, error) {
+func parseFilterAnd(lex *lexer, fieldName string) (filter, error) {
 	var filters []filter
 	for {
 		f, err := parseGenericFilter(lex, fieldName)
@@ -320,7 +320,7 @@ func parseGenericFilter(lex *lexer, fieldName string) (filter, error) {
 		}
 		return parseParensFilter(lex, fieldName)
 	case lex.isKeyword("not", "!"):
-		return parseNotFilter(lex, fieldName)
+		return parseFilterNot(lex, fieldName)
 	case lex.isKeyword("exact"):
 		return parseExactFilter(lex, fieldName)
 	case lex.isKeyword("i"):
@@ -444,7 +444,7 @@ func parseParensFilter(lex *lexer, fieldName string) (filter, error) {
 	if !lex.mustNextToken() {
 		return nil, fmt.Errorf("missing filter after '('")
 	}
-	f, err := parseOrFilter(lex, fieldName)
+	f, err := parseFilterOr(lex, fieldName)
 	if err != nil {
 		return nil, err
 	}
@@ -455,7 +455,7 @@ func parseParensFilter(lex *lexer, fieldName string) (filter, error) {
 	return f, nil
 }
 
-func parseNotFilter(lex *lexer, fieldName string) (filter, error) {
+func parseFilterNot(lex *lexer, fieldName string) (filter, error) {
 	notKeyword := lex.token
 	if !lex.mustNextToken() {
 		return nil, fmt.Errorf("missing filters after '%s'", notKeyword)
@@ -464,14 +464,14 @@ func parseNotFilter(lex *lexer, fieldName string) (filter, error) {
 	if err != nil {
 		return nil, err
 	}
-	nf, ok := f.(*notFilter)
+	fn, ok := f.(*filterNot)
 	if ok {
-		return nf.f, nil
+		return fn.f, nil
 	}
-	nf = &notFilter{
+	fn = &filterNot{
 		f: f,
 	}
-	return nf, nil
+	return fn, nil
 }
 
 func parseAnyCaseFilter(lex *lexer, fieldName string) (filter, error) {
diff --git a/lib/logstorage/storage_search.go b/lib/logstorage/storage_search.go
index 29f614d6a..b09bfba85 100644
--- a/lib/logstorage/storage_search.go
+++ b/lib/logstorage/storage_search.go
@@ -343,7 +343,7 @@ func hasStreamFilters(f filter) bool {
 		return hasStreamFiltersInList(t.filters)
 	case *filterOr:
 		return hasStreamFiltersInList(t.filters)
-	case *notFilter:
+	case *filterNot:
 		return hasStreamFilters(t.f)
 	case *streamFilter:
 		return true
@@ -371,8 +371,8 @@ func initStreamFilters(tenantIDs []TenantID, idb *indexdb, f filter) filter {
 		return &filterOr{
 			filters: initStreamFiltersList(tenantIDs, idb, t.filters),
 		}
-	case *notFilter:
-		return &notFilter{
+	case *filterNot:
+		return &filterNot{
 			f: initStreamFilters(tenantIDs, idb, t.f),
 		}
 	case *streamFilter: