From 1eaffc7eec149557e41ccbf8b52897b446cb5f41 Mon Sep 17 00:00:00 2001
From: Ben Ye <benye@amazon.com>
Date: Tue, 23 Apr 2024 11:34:30 -0700
Subject: [PATCH] Optimize empty posting check in lazy posting (#7298)

* change lazy postings empty posting check to use cardinality

Signed-off-by: Ben Ye <benye@amazon.com>

* update lazy posting test

Signed-off-by: Ben Ye <benye@amazon.com>

---------

Signed-off-by: Ben Ye <benye@amazon.com>
---
 pkg/store/lazy_postings.go      | 14 +++++---------
 pkg/store/lazy_postings_test.go | 15 +++++++++++++++
 2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/pkg/store/lazy_postings.go b/pkg/store/lazy_postings.go
index 0f4038bc61d..9469be9b472 100644
--- a/pkg/store/lazy_postings.go
+++ b/pkg/store/lazy_postings.go
@@ -54,15 +54,6 @@ func optimizePostingsFetchByDownloadedBytes(r *bucketIndexReader, postingGroups
 			return nil, false, errors.Wrapf(err, "postings offsets for %s", pg.name)
 		}
 
-		// If the posting group adds keys, no posting ranges found means empty posting.
-		if len(pg.addKeys) > 0 && len(rngs) == 0 {
-			return nil, true, nil
-		}
-		// If the posting group removes keys, no posting ranges found is fine. It means
-		// that the posting group is a noop. {job != "some_non_existent_value"}
-		if len(pg.removeKeys) > 0 && len(rngs) == 0 {
-			continue
-		}
 		for _, r := range rngs {
 			if r == indexheader.NotFoundRange {
 				continue
@@ -72,6 +63,11 @@ func optimizePostingsFetchByDownloadedBytes(r *bucketIndexReader, postingGroups
 			// https://github.com/prometheus/prometheus/blob/v2.46.0/tsdb/docs/format/index.md.
 			pg.cardinality += (r.End - r.Start - 4) / 4
 		}
+		// If the posting group adds keys, 0 cardinality means the posting doesn't exist.
+		// If the posting group removes keys, no posting ranges found is fine as it is a noop.
+		if len(pg.addKeys) > 0 && pg.cardinality == 0 {
+			return nil, true, nil
+		}
 	}
 	slices.SortFunc(postingGroups, func(a, b *postingGroup) int {
 		if a.cardinality == b.cardinality {
diff --git a/pkg/store/lazy_postings_test.go b/pkg/store/lazy_postings_test.go
index 53f96502344..08e30b6d5ba 100644
--- a/pkg/store/lazy_postings_test.go
+++ b/pkg/store/lazy_postings_test.go
@@ -352,6 +352,21 @@ func TestOptimizePostingsFetchByDownloadedBytes(t *testing.T) {
 				{name: "foo", addKeys: []string{"bar"}, cardinality: 1},
 			},
 		},
+		{
+			name: "posting group label with add keys exist but no matching value, expect empty posting",
+			inputPostings: map[string]map[string]index.Range{
+				"foo": {"bar": index.Range{End: 8}},
+				"bar": {"baz": index.Range{Start: 8, End: 16}},
+			},
+			seriesMaxSize:    1000,
+			seriesMatchRatio: 0.5,
+			postingGroups: []*postingGroup{
+				{name: "foo", addKeys: []string{"bar"}},
+				{name: "bar", addKeys: []string{"foo"}},
+			},
+			expectedPostingGroups: nil,
+			expectedEmptyPosting:  true,
+		},
 		{
 			name: "posting group label with remove keys exist but no matching value, noop",
 			inputPostings: map[string]map[string]index.Range{