chore(dataobj-index): Handle special cases in the section lookup of the metastore (#19203)

There are three edge cases that this PR improves:

* No table (toc) paths could be resolved: return early with empty result
* No index paths could be resolved: return early with empty result
* No relevant sections could be resolved: return with empty result instead of with an error

Signed-off-by: Christian Haudum <christian.haudum@gmail.com>

Author: chaudum

pkg/dataobj/metastore/object.go

@@ -217,6 +217,15 @@ func (m *ObjectMetastore) Sections(ctx context.Context, start, end time.Time, ma
 		tablePaths = append(tablePaths, path)
 	}
 
+	// Return early if no toc files are found
+	if len(tablePaths) == 0 {
+		m.metrics.indexObjectsTotal.Observe(0)
+		m.metrics.resolvedSectionsTotal.Observe(0)
+		duration := sectionsTimer.ObserveDuration()
+		level.Debug(utillog.WithContext(ctx, m.logger)).Log("msg", "resolved sections", "duration", duration, "sections", 0)
+		return nil, nil
+	}
+
 	// List index objects from all tables concurrently
 	indexPaths, err := m.listObjectsFromTables(ctx, tablePaths, start, end)
 	if err != nil {
@@ -226,6 +235,14 @@ func (m *ObjectMetastore) Sections(ctx context.Context, start, end time.Time, ma
 	level.Debug(m.logger).Log("msg", "resolved index files", "count", len(indexPaths), "paths", strings.Join(indexPaths, ","))
 	m.metrics.indexObjectsTotal.Observe(float64(len(indexPaths)))
 
+	// Return early if no index files are found
+	if len(indexPaths) == 0 {
+		m.metrics.resolvedSectionsTotal.Observe(0)
+		duration := sectionsTimer.ObserveDuration()
+		level.Debug(utillog.WithContext(ctx, m.logger)).Log("msg", "resolved sections", "duration", duration, "sections", 0)
+		return nil, nil
+	}
+
 	// init index files
 	indexObjects := make([]*dataobj.Object, len(indexPaths))
 	g, initCtx := errgroup.WithContext(ctx)
@@ -262,9 +279,6 @@ func (m *ObjectMetastore) Sections(ctx context.Context, start, end time.Time, ma
 		}
 
 		streamSectionPointers = intersectSections(streamSectionPointers, sectionMembershipEstimates)
-		if len(streamSectionPointers) == 0 {
-			return nil, errors.New("no relevant sections returned")
-		}
 	}
 
 	duration := sectionsTimer.ObserveDuration()

pkg/dataobj/metastore/object_test.go

@@ -311,12 +311,15 @@ func TestSectionsForStreamMatchers(t *testing.T) {
 		name       string
 		matchers   []*labels.Matcher
 		predicates []*labels.Matcher
+		start, end time.Time
 		wantCount  int
 	}{
 		{
 			name:       "no matchers returns no sections",
 			matchers:   nil,
 			predicates: nil,
+			start:      now.Add(-time.Hour),
+			end:        now.Add(time.Hour),
 			wantCount:  0,
 		},
 		{
@@ -325,6 +328,8 @@ func TestSectionsForStreamMatchers(t *testing.T) {
 				labels.MustNewMatcher(labels.MatchEqual, "app", "foo"),
 			},
 			predicates: nil,
+			start:      now.Add(-time.Hour),
+			end:        now.Add(time.Hour),
 			wantCount:  1,
 		},
 		{
@@ -333,6 +338,8 @@ func TestSectionsForStreamMatchers(t *testing.T) {
 				labels.MustNewMatcher(labels.MatchEqual, "app", "doesnotexist"),
 			},
 			predicates: nil,
+			start:      now.Add(-time.Hour),
+			end:        now.Add(time.Hour),
 			wantCount:  0,
 		},
 		{
@@ -343,13 +350,37 @@ func TestSectionsForStreamMatchers(t *testing.T) {
 			predicates: []*labels.Matcher{
 				labels.MustNewMatcher(labels.MatchRegexp, "bar", "something"),
 			},
+			start:     now.Add(-time.Hour),
+			end:       now.Add(time.Hour),
 			wantCount: 1,
 		},
+		{
+			name: "stream matcher with not matching predicate returns no matching sections",
+			matchers: []*labels.Matcher{
+				labels.MustNewMatcher(labels.MatchEqual, "app", "foo"),
+			},
+			predicates: []*labels.Matcher{
+				labels.MustNewMatcher(labels.MatchEqual, "bar", "something"),
+			},
+			start:     now.Add(-time.Hour),
+			end:       now.Add(time.Hour),
+			wantCount: 0,
+		},
+		{
+			name: "matcher returns no matching sections if time range is out of bounds",
+			matchers: []*labels.Matcher{
+				labels.MustNewMatcher(labels.MatchEqual, "app", "foo"),
+			},
+			predicates: nil,
+			start:      now.Add(-3 * time.Hour),
+			end:        now.Add(-2 * time.Hour),
+			wantCount:  0,
+		},
 	}
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			sections, err := mstore.Sections(ctx, now.Add(-time.Hour), now.Add(time.Hour), tt.matchers, tt.predicates)
+			sections, err := mstore.Sections(ctx, tt.start, tt.end, tt.matchers, tt.predicates)
 			require.NoError(t, err)
 			require.Len(t, sections, tt.wantCount)
 			for _, section := range sections {