lib/storage: move the conversion of tag filters to composite tag filters into indexSearch.searchMetricIDsInternal

This makes the code less fragile - it is harder to skip the convertToCompositeTagFilterss() call now.
While at it, call indexSearch.containsTimeRange() inside indexSearch.searchMetricIDsInternal()
in order to quickly terminate search of time series in the old indexdb for new time ranges.

Updates https://github.com/VictoriaMetrics/VictoriaMetrics/issues/5055

This is a follow-up for 2d31fd7855

lib/storage/index_db.go

@@ -570,10 +570,6 @@ func (db *indexDB) SearchLabelNamesWithFiltersOnTimeRange(qt *querytracer.Tracer
 	qt = qt.NewChild("search for label names: filters=%s, timeRange=%s, maxLabelNames=%d, maxMetrics=%d", tfss, &tr, maxLabelNames, maxMetrics)
 	defer qt.Done()
 
-	if tr.MinTimestamp >= db.s.minTimestampForCompositeIndex {
-		tfss = convertToCompositeTagFilterss(tfss)
-	}
-
 	lns := make(map[string]struct{})
 	qtChild := qt.NewChild("search for label names in the current indexdb")
 	is := db.getIndexSearch(deadline)
@@ -730,7 +726,9 @@ func (is *indexSearch) searchLabelNamesWithFiltersOnDate(qt *querytracer.Tracer,
 }
 
 func (is *indexSearch) getLabelNamesForMetricIDs(qt *querytracer.Tracer, metricIDs []uint64, lns map[string]struct{}, maxLabelNames int) {
-	lns["__name__"] = struct{}{}
+	if len(metricIDs) > 0 {
+		lns["__name__"] = struct{}{}
+	}
 	var mn MetricName
 	foundLabelNames := 0
 	var buf []byte
@@ -765,10 +763,6 @@ func (db *indexDB) SearchLabelValuesWithFiltersOnTimeRange(qt *querytracer.Trace
 	qt = qt.NewChild("search for label values: labelName=%q, filters=%s, timeRange=%s, maxLabelNames=%d, maxMetrics=%d", labelName, tfss, &tr, maxLabelValues, maxMetrics)
 	defer qt.Done()
 
-	if tr.MinTimestamp >= db.s.minTimestampForCompositeIndex {
-		tfss = convertToCompositeTagFilterss(tfss)
-	}
-
 	lvs := make(map[string]struct{})
 	qtChild := qt.NewChild("search for label values in the current indexdb")
 	is := db.getIndexSearch(deadline)
@@ -1185,10 +1179,6 @@ func (is *indexSearch) getSeriesCount() (uint64, error) {
 func (db *indexDB) GetTSDBStatus(qt *querytracer.Tracer, tfss []*TagFilters, date uint64, focusLabel string, topN, maxMetrics int, deadline uint64) (*TSDBStatus, error) {
 	qtChild := qt.NewChild("collect tsdb stats in the current indexdb")
 
-	if int64(date*msecPerDay) >= db.s.minTimestampForCompositeIndex {
-		tfss = convertToCompositeTagFilterss(tfss)
-	}
-
 	is := db.getIndexSearch(deadline)
 	status, err := is.getTSDBStatus(qtChild, tfss, date, focusLabel, topN, maxMetrics)
 	qtChild.Done()
@@ -1493,7 +1483,6 @@ func (db *indexDB) DeleteTSIDs(qt *querytracer.Tracer, tfss []*TagFilters) (int,
 	if len(tfss) == 0 {
 		return 0, nil
 	}
-	tfss = convertToCompositeTagFilterss(tfss)
 
 	// Obtain metricIDs to delete.
 	tr := TimeRange{
@@ -1599,9 +1588,6 @@ func (db *indexDB) searchMetricIDs(qt *querytracer.Tracer, tfss []*TagFilters, t
 	if len(tfss) == 0 {
 		return nil, nil
 	}
-	if tr.MinTimestamp >= db.s.minTimestampForCompositeIndex {
-		tfss = convertToCompositeTagFilterss(tfss)
-	}
 
 	qtChild := qt.NewChild("search for metricIDs in the current indexdb")
 	tfKeyBuf := tagFiltersKeyBufPool.Get()
@@ -2131,14 +2117,6 @@ func (is *indexSearch) searchMetricIDsWithFiltersOnDate(qt *querytracer.Tracer,
 //
 // The returned metricIDs are sorted.
 func (is *indexSearch) searchMetricIDs(qt *querytracer.Tracer, tfss []*TagFilters, tr TimeRange, maxMetrics int) ([]uint64, error) {
-	ok, err := is.containsTimeRange(tr)
-	if err != nil {
-		return nil, err
-	}
-	if !ok {
-		// Fast path - the index doesn't contain data for the given tr.
-		return nil, nil
-	}
 	metricIDs, err := is.searchMetricIDsInternal(qt, tfss, tr, maxMetrics)
 	if err != nil {
 		return nil, err
@@ -2170,7 +2148,23 @@ func (is *indexSearch) searchMetricIDs(qt *querytracer.Tracer, tfss []*TagFilter
 func (is *indexSearch) searchMetricIDsInternal(qt *querytracer.Tracer, tfss []*TagFilters, tr TimeRange, maxMetrics int) (*uint64set.Set, error) {
 	qt = qt.NewChild("search for metric ids: filters=%s, timeRange=%s, maxMetrics=%d", tfss, &tr, maxMetrics)
 	defer qt.Done()
+
 	metricIDs := &uint64set.Set{}
+
+	ok, err := is.containsTimeRange(tr)
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		qt.Printf("indexdb doesn't contain data for the given timeRange=%s", &tr)
+		return metricIDs, nil
+	}
+
+	if tr.MinTimestamp >= is.db.s.minTimestampForCompositeIndex {
+		tfss = convertToCompositeTagFilterss(tfss)
+		qt.Printf("composite filters=%s", tfss)
+	}
+
 	for _, tfs := range tfss {
 		if len(tfs.tfs) == 0 {
 			// An empty filters must be equivalent to `{__name__!=""}`