Make sure on a miss from a starting sequence that if no other msgs exists we avoid loading and blocks.

Signed-off-by: Derek Collison <derek@nats.io>

Author: derekcollison

server/filestore.go

@@ -2596,28 +2596,38 @@ func (fs *fileStore) FilteredState(sseq uint64, subj string) SimpleState {
 
 // This is used to see if we can selectively jump start blocks based on filter subject and a floor block index.
 // Will return -1 if no matches at all.
-func (fs *fileStore) checkSkipFirstBlock(filter string, wc bool) int {
-	start := uint32(math.MaxUint32)
+func (fs *fileStore) checkSkipFirstBlock(filter string, wc bool) (int, int) {
+	start, stop := uint32(math.MaxUint32), uint32(0)
 	if wc {
 		fs.psim.Match(stringToBytes(filter), func(_ []byte, psi *psi) {
 			if psi.fblk < start {
 				start = psi.fblk
 			}
+			if psi.lblk > stop {
+				stop = psi.lblk
+			}
 		})
 	} else if psi, ok := fs.psim.Find(stringToBytes(filter)); ok {
-		start = psi.fblk
+		start, stop = psi.fblk, psi.lblk
 	}
 	// Nothing found.
 	if start == uint32(math.MaxUint32) {
-		return -1
+		return -1, -1
 	}
-	// Here we need to translate this to index into fs.blks.
+	// Here we need to translate this to index into fs.blks properly.
 	mb := fs.bim[start]
 	if mb == nil {
-		return -1
+		return -1, -1
 	}
-	bi, _ := fs.selectMsgBlockWithIndex(atomic.LoadUint64(&mb.last.seq))
-	return bi
+	fi, _ := fs.selectMsgBlockWithIndex(atomic.LoadUint64(&mb.last.seq))
+
+	mb = fs.bim[stop]
+	if mb == nil {
+		return -1, -1
+	}
+	li, _ := fs.selectMsgBlockWithIndex(atomic.LoadUint64(&mb.last.seq))
+
+	return fi, li
 }
 
 // Optimized way for getting all num pending matching a filter subject.
@@ -6475,9 +6485,9 @@ func (fs *fileStore) LoadNextMsg(filter string, wc bool, start uint64, sm *Store
 				// Similar to above if start <= first seq.
 				// TODO(dlc) - For v2 track these by filter subject since they will represent filtered consumers.
 				if i == bi {
-					nbi := fs.checkSkipFirstBlock(filter, wc)
+					nbi, lbi := fs.checkSkipFirstBlock(filter, wc)
 					// Nothing available.
-					if nbi < 0 {
+					if nbi < 0 || lbi <= bi {
 						return nil, fs.state.LastSeq, ErrStoreEOF
 					}
 					// See if we can jump ahead here.

server/filestore_test.go

@@ -7263,6 +7263,58 @@ func TestFileStoreFilteredPendingPSIMFirstBlockUpdateNextBlock(t *testing.T) {
 	require_Equal(t, psi.lblk, 4)
 }
 
+func TestFileStoreLargeSparseMsgsDoNotLoadAfterLast(t *testing.T) {
+	sd := t.TempDir()
+	fs, err := newFileStore(
+		FileStoreConfig{StoreDir: sd, BlockSize: 128},
+		StreamConfig{Name: "zzz", Subjects: []string{"foo.*.*"}, Storage: FileStorage})
+	require_NoError(t, err)
+	defer fs.Stop()
+
+	msg := []byte("hello")
+	// Create 2 blocks with each, each block holds 2 msgs
+	for i := 0; i < 2; i++ {
+		fs.StoreMsg("foo.22.bar", nil, msg)
+		fs.StoreMsg("foo.22.baz", nil, msg)
+	}
+	// Now create 8 more blocks with just baz. So no matches for these 8 blocks
+	// for "foo.22.bar".
+	for i := 0; i < 8; i++ {
+		fs.StoreMsg("foo.22.baz", nil, msg)
+		fs.StoreMsg("foo.22.baz", nil, msg)
+	}
+	require_Equal(t, fs.numMsgBlocks(), 10)
+
+	// Remove all blk cache and fss.
+	fs.mu.RLock()
+	for _, mb := range fs.blks {
+		mb.mu.Lock()
+		mb.fss, mb.cache = nil, nil
+		mb.mu.Unlock()
+	}
+	fs.mu.RUnlock()
+
+	// "foo.22.bar" is at sequence 1 and 3.
+	// Make sure if we do a LoadNextMsg() starting at 4 that we do not load
+	// all the tail blocks.
+	_, _, err = fs.LoadNextMsg("foo.*.bar", true, 4, nil)
+	require_Error(t, err, ErrStoreEOF)
+
+	// Now make sure we did not load fss and cache.
+	var loaded int
+	fs.mu.RLock()
+	for _, mb := range fs.blks {
+		mb.mu.RLock()
+		if mb.cache != nil || mb.fss != nil {
+			loaded++
+		}
+		mb.mu.RUnlock()
+	}
+	fs.mu.RUnlock()
+	// We will load first block for starting seq 4, but no others should have loaded.
+	require_Equal(t, loaded, 1)
+}
+
 ///////////////////////////////////////////////////////////////////////////
 // Benchmarks
 ///////////////////////////////////////////////////////////////////////////
@@ -7520,3 +7572,32 @@ func Benchmark_FileStoreLoadNextMsgVerySparseMsgsInBetweenWithWildcard(b *testin
 		require_NoError(b, err)
 	}
 }
+
+func Benchmark_FileStoreLoadNextMsgVerySparseMsgsLargeTail(b *testing.B) {
+	fs, err := newFileStore(
+		FileStoreConfig{StoreDir: b.TempDir()},
+		StreamConfig{Name: "zzz", Subjects: []string{"foo.*.*"}, Storage: FileStorage})
+	require_NoError(b, err)
+	defer fs.Stop()
+
+	// Small om purpose.
+	msg := []byte("ok")
+
+	// Make first msg one that would match as well.
+	fs.StoreMsg("foo.1.baz", nil, msg)
+	// Add in a bunch of msgs.
+	// We need to make sure we have a range of subjects that could kick in a linear scan.
+	for i := 0; i < 1_000_000; i++ {
+		subj := fmt.Sprintf("foo.%d.bar", rand.Intn(100_000)+2)
+		fs.StoreMsg(subj, nil, msg)
+	}
+
+	b.ResetTimer()
+
+	var smv StoreMsg
+	for i := 0; i < b.N; i++ {
+		// Make sure not first seq.
+		_, _, err := fs.LoadNextMsg("foo.*.baz", true, 2, &smv)
+		require_Error(b, err, ErrStoreEOF)
+	}
+}