lib/logstorage: fix uniq_values merge in cluster queries

apptest/tests/vlcluster_test.go

@@ -8,6 +8,34 @@ import (
 	"github.com/VictoriaMetrics/VictoriaLogs/apptest"
 )
 
+// TestVlclusterUniqValuesMerge verifies that uniq_values correctly merges results when some storage nodes have no matching values.
+func TestVlclusterUniqValuesMerge(t *testing.T) {
+	fs.MustRemoveDir(t.Name())
+	tc := apptest.NewTestCase(t)
+	defer tc.Stop()
+	sut := tc.MustStartDefaultVlcluster()
+
+	// Write the same group to two storage nodes. The first node has no x values,
+	// while the second node has x values. This exercises merging a non-empty
+	// uniq_values state into an empty destination state at vlselect.
+	storage0 := sut.StorageNode(0)
+	storage0.JSONLineWrite(t, []string{
+		`{"_msg":"no x","host":"h1","_time":"2025-01-01T01:00:00Z"}`,
+	}, apptest.IngestOpts{})
+	storage0.ForceFlush(t)
+
+	storage1 := sut.StorageNode(1)
+	storage1.JSONLineWrite(t, []string{
+		`{"_msg":"has x","host":"h1","x":"a","_time":"2025-01-01T01:00:00Z"}`,
+	}, apptest.IngestOpts{})
+	storage1.ForceFlush(t)
+
+	got := sut.LogsQLQuery(t, `* | stats by (host) uniq_values(x) as values`, apptest.QueryOpts{})
+	assertLogsQLResponseEqual(t, got, &apptest.LogsQLQueryResponse{
+		LogLines: []string{`{"host":"h1","values":"[\"a\"]"}`},
+	})
+}
+
 // TestVlclusterIngestAndQuery verifies that logs are correctly ingested and queried from cluster.
 func TestVlclusterIngestAndQuery(t *testing.T) {
 	fs.MustRemoveDir(t.Name())

apptest/vlcluster.go

@@ -225,6 +225,11 @@ func (app *Vlcluster) LogsQLQueryRaw(t *testing.T, query string, opts QueryOpts)
 	return app.selectNode.cli.PostForm(t, url, values)
 }
 
+// StorageNode returns the i-th storage node, allowing direct log ingestion that bypasses the insert node.
+func (app *Vlcluster) StorageNode(i int) *Vlsingle {
+	return app.storageNodes[i]
+}
+
 // String returns the string representation of the app state.
 func (app *Vlcluster) String() string {
 	return "Vlcluster"

docs/victorialogs/CHANGELOG.md

@@ -34,6 +34,7 @@ according to the following docs:
 * FEATURE: [dashboards/kubernetes-explorer](https://github.com/VictoriaMetrics/VictoriaLogs/blob/master/dashboards/victorialogs-kubernetes-explorer.json): add new dashboard for exploring Kubernetes logs via [VictoriaLogs datasource](https://docs.victoriametrics.com/victorialogs/integrations/grafana/) in Grafana. Thanks to @sias32 for [the contribution](https://github.com/VictoriaMetrics/VictoriaLogs/pull/1254)!
 * FEATURE: [File Collector](https://docs.victoriametrics.com/victorialogs/vlagent/#collect-logs-from-files): enhance glob pattern support with additional syntax: double-star `/**/` for matching nested directories (e.g. `/var/log/**/*.log`), alternatives `{a,b}` for matching multiple specific names (e.g. `{access,error}.log`), character classes `[a-z]` and `?` wildcard for single-character matching. See [#1393](https://github.com/VictoriaMetrics/VictoriaLogs/issues/1393) and [these docs](https://docs.victoriametrics.com/victorialogs/vlagent/#glob-pattern-requirements) for the full pattern syntax reference.
 
+* BUGFIX: [LogsQL](https://docs.victoriametrics.com/victorialogs/logsql/): fix panic when using [`uniq_values()`](https://docs.victoriametrics.com/victorialogs/logsql/#uniq_values-stats) in the [`stats` pipe](https://docs.victoriametrics.com/victorialogs/logsql/#stats-pipe) in VictoriaLogs cluster when some `vlstorage` nodes return no values for the requested field while other `vlstorage` nodes return values for the same group. See [#1383](https://github.com/VictoriaMetrics/VictoriaLogs/issues/1383).
 * BUGFIX: [LogsQL](https://docs.victoriametrics.com/victorialogs/logsql/): fix [`unroll` pipe](https://docs.victoriametrics.com/victorialogs/logsql/#unroll-pipe) and [`json_array_len` pipe](https://docs.victoriametrics.com/victorialogs/logsql/#json_array_len-pipe) ignoring JSON arrays preceded by whitespace. See [#1427](https://github.com/VictoriaMetrics/VictoriaLogs/issues/1427).
 * BUGFIX: [vlagent](https://docs.victoriametrics.com/victorialogs/vlagent/): hide sensitive values passed via `-remoteWrite.proxyURL` in `/metrics`, `/flags`, and startup logs. Previously these values could be exposed in plain text. See [#1320](https://github.com/VictoriaMetrics/VictoriaLogs/pull/1320).
 * BUGFIX: [web UI](https://docs.victoriametrics.com/victorialogs/querying/#web-ui): sanitize markdown URLs in logs rendered with `markdown parsing` enabled, allowing only `http`, `https`, `mailto`, and `tel` schemes for active links and images. See [#1313](https://github.com/VictoriaMetrics/VictoriaLogs/pull/1313).

lib/logstorage/stats_uniq_values.go

@@ -150,6 +150,9 @@ func (sup *statsUniqValuesProcessor) mergeState(_ *chunkedAllocator, sf statsFun
 		return
 	}
 
+	if sup.m == nil {
+		sup.m = make(map[string]struct{}, len(src.m))
+	}
 	for k := range src.m {
 		if _, ok := sup.m[k]; !ok {
 			sup.m[k] = struct{}{}