update comment

.golangci.yml

@@ -1,9 +1,18 @@
 version: "2"
 linters:
+  enable:
+    - errorlint
   settings:
     errcheck:
       exclude-functions:
         - (net/http.ResponseWriter).Write
+    errorlint:
+      errorf: true
+      # Do not enable `comparison` and `asserts`: they produce false positives,
+      # since many call sites intentionally compare sentinel errors directly (e.g. err == io.EOF)
+      # when the producer is documented to return them unwrapped. See https://github.com/VictoriaMetrics/VictoriaLogs/pull/1490
+      comparison: false
+      asserts: false
   exclusions:
     generated: lax
     presets:

app/vmctl/utils.go

@@ -74,9 +74,9 @@ func wrapErr(vmErr *vm.ImportError, verbose bool) error {
 		verboseMsg = "(enable `--verbose` output to get more details)"
 	}
 	if vmErr.Err == nil {
-		return fmt.Errorf("%s\n\tLatest delivered batch for timestamps range %d - %d %s\n%s",
+		return fmt.Errorf("%w\n\tLatest delivered batch for timestamps range %d - %d %s\n%s",
 			vmErr.Err, minTS, maxTS, verboseMsg, errTS)
 	}
-	return fmt.Errorf("%s\n\tImporting batch failed for timestamps range %d - %d %s\n%s",
+	return fmt.Errorf("%w\n\tImporting batch failed for timestamps range %d - %d %s\n%s",
 		vmErr.Err, minTS, maxTS, verboseMsg, errTS)
 }

lib/mergeset/table_search_timing_test.go

@@ -94,7 +94,7 @@ func benchmarkTableSearchKeysExt(b *testing.B, tb *Table, keys [][]byte, stripSu
 				}
 				ts.Seek(searchKey)
 				if !ts.NextItem() {
-					panic(fmt.Errorf("BUG: NextItem must return true for searchKeys[%d]=%q; err=%v", i, searchKey, ts.Error()))
+					panic(fmt.Errorf("BUG: NextItem must return true for searchKeys[%d]=%q; err=%w", i, searchKey, ts.Error()))
 				}
 				if !bytes.HasPrefix(ts.Item, searchKey) {
 					panic(fmt.Errorf("BUG: unexpected item found for searchKey[%d]=%q; got %q; want %q", i, searchKey, ts.Item, key))

lib/storage/index_db.go

@@ -1242,9 +1242,12 @@ func (db *indexDB) GetSeriesCount(deadline uint64) (uint64, error) {
 func (is *indexSearch) getSeriesCount() (uint64, error) {
 	ts := &is.ts
 	kb := &is.kb
+	mp := &is.mp
 	loopsPaceLimiter := 0
 	var metricIDsLen uint64
-	kb.B = is.marshalCommonPrefix(kb.B[:0], nsPrefixMetricIDToTSID)
+	// Extract the number of series from ((__name__=value): metricIDs) rows
+	kb.B = is.marshalCommonPrefix(kb.B[:0], nsPrefixTagToMetricIDs)
+	kb.B = marshalTagValue(kb.B, nil)
 	ts.Seek(kb.B)
 	for ts.NextItem() {
 		if loopsPaceLimiter&paceLimiterFastIterationsMask == 0 {
@@ -1257,10 +1260,19 @@ func (is *indexSearch) getSeriesCount() (uint64, error) {
 		if !bytes.HasPrefix(item, kb.B) {
 			break
 		}
+		tail := item[len(kb.B):]
+		n := bytes.IndexByte(tail, tagSeparatorChar)
+		if n < 0 {
+			return 0, fmt.Errorf("invalid tag->metricIDs line %q: cannot find tagSeparatorChar %d", item, tagSeparatorChar)
+		}
+		tail = tail[n+1:]
+		if err := mp.InitOnlyTail(item, tail); err != nil {
+			return 0, err
+		}
 		// Take into account deleted timeseries too.
 		// It is OK if series can be counted multiple times in rare cases -
 		// the returned number is an estimation.
-		metricIDsLen++
+		metricIDsLen += uint64(mp.MetricIDsLen())
 	}
 	if err := ts.Error(); err != nil {
 		return 0, fmt.Errorf("error when counting unique timeseries: %w", err)