LoadNextMsgMulti and LoadPrevMsgMulti use fast path for single filter

Signed-off-by: Neil Twigg <neil@nats.io>

Author: neilalexander

server/filestore.go

@@ -8369,6 +8369,9 @@ func (fs *fileStore) LoadNextMsgMulti(sl *gsl.SimpleSublist, start uint64, smp *
 	if sl == nil || sl.MatchesFullWildcard() {
 		return fs.LoadNextMsg(_EMPTY_, false, start, smp)
 	}
+	if filter, ok := sl.MatchesSingleFilter(); ok {
+		return fs.LoadNextMsg(filter, subjectHasWildcard(filter), start, smp)
+	}
 	fs.mu.RLock()
 	defer fs.mu.RUnlock()
 
@@ -8702,6 +8705,9 @@ func (fs *fileStore) LoadPrevMsgMulti(sl *gsl.SimpleSublist, start uint64, smp *
 	if sl == nil || sl.MatchesFullWildcard() {
 		return fs.LoadPrevMsg(_EMPTY_, false, start, smp)
 	}
+	if filter, ok := sl.MatchesSingleFilter(); ok {
+		return fs.LoadPrevMsg(filter, subjectHasWildcard(filter), start, smp)
+	}
 	fs.mu.RLock()
 	defer fs.mu.RUnlock()
 

server/gsl/gsl.go

@@ -194,7 +194,9 @@ func singleFilter[T comparable](l *level[T], filter string) (string, bool) {
 	if l == nil {
 		return filter, filter != _EMPTY_
 	}
-
+	if len(l.nodes) > 1 {
+		return _EMPTY_, false
+	}
 	var next *node[T]
 	branches := 0
 	if l.pwc != nil {
@@ -208,7 +210,6 @@ func singleFilter[T comparable](l *level[T], filter string) (string, bool) {
 	for _, n := range l.nodes {
 		next = n
 		branches++
-		break
 	}
 	if branches != 1 {
 		return _EMPTY_, false
@@ -221,7 +222,7 @@ func singleFilter[T comparable](l *level[T], filter string) (string, bool) {
 		return filter, filter != _EMPTY_
 	}
 	if filter != _EMPTY_ {
-		if _, ok := singleFilter(next.next, _EMPTY_); ok {
+		if next.next.numNodes() > 0 {
 			return _EMPTY_, false
 		}
 		return filter, true

server/gsl/gsl_test.go

@@ -275,10 +275,32 @@ func TestGenericSublistSingleFilter(t *testing.T) {
 	require_True(t, ok)
 	require_Equal(t, filter, "stream.A.child")
 
+	require_NoError(t, s.Insert("stream.A.other", 22))
+	filter, ok = s.MatchesSingleFilter()
+	require_False(t, ok)
+	require_Equal(t, filter, _EMPTY_)
+
 	require_NoError(t, s.Insert("stream.*", 33))
 	filter, ok = s.MatchesSingleFilter()
 	require_False(t, ok)
 	require_Equal(t, filter, _EMPTY_)
+
+	// Test that an ancestor with descendants correctly returns false.
+	s2 := NewSublist[int]()
+	require_NoError(t, s2.Insert("foo", 1))
+	require_NoError(t, s2.Insert("foo.bar", 2))
+	require_NoError(t, s2.Insert("foo.baz", 3))
+	filter, ok = s2.MatchesSingleFilter()
+	require_False(t, ok)
+	require_Equal(t, filter, _EMPTY_)
+
+	// Test that an ancestor with only descendants correctly returns false.
+	s3 := NewSublist[int]()
+	require_NoError(t, s3.Insert("foo.bar", 2))
+	require_NoError(t, s3.Insert("foo.baz", 3))
+	filter, ok = s3.MatchesSingleFilter()
+	require_False(t, ok)
+	require_Equal(t, filter, _EMPTY_)
 }
 
 // TestGenericSublistHasInterestStartingInRace tests that HasInterestStartingIn

server/memstore.go

@@ -1975,7 +1975,7 @@ func (ms *memStore) LoadPrevMsgMulti(sl *gsl.SimpleSublist, start uint64, smp *S
 			return smp, nseq, nil
 		}
 	}
-	return nil, ms.state.LastSeq, ErrStoreEOF
+	return nil, ms.state.FirstSeq, ErrStoreEOF
 }
 
 // RemoveMsg will remove the message from this store.