Addressed review comments

Signed-off-by: Marco Pracucci <marco@pracucci.com>

tsdb/index/postings.go

@@ -853,16 +853,6 @@ type PostingsCloner struct {
 // and it shouldn't be used once provided to the PostingsCloner.
 func NewPostingsCloner(p Postings) *PostingsCloner {
 	ids, err := ExpandPostings(p)
-
-	// The ExpandedPostings() doesn't know the total number of postings beforehand,
-	// so the returned slice capacity may be well above the actual number of items.
-	// In such case, we shrink it.
-	if float64(len(ids)) < float64(cap(ids))*0.70 {
-		shrunk := make([]storage.SeriesRef, len(ids))
-		copy(shrunk, ids)
-		ids = shrunk
-	}
-
 	return &PostingsCloner{ids: ids, err: err}
 }
 

tsdb/index/postings_test.go

@@ -24,7 +24,6 @@ import (
 	"testing"
 
 	"github.com/pkg/errors"
-	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
 	"github.com/prometheus/prometheus/model/labels"
@@ -1104,20 +1103,6 @@ func TestPostingsCloner(t *testing.T) {
 	})
 }
 
-func TestNewPostingsCloner_ShrinkExpandedPostingsSlice(t *testing.T) {
-	t.Run("should not shrink expanded postings if length is >= 70% capacity", func(t *testing.T) {
-		cloner := NewPostingsCloner(NewListPostings(make([]storage.SeriesRef, 60)))
-		assert.Equal(t, 60, len(cloner.ids))
-		assert.Equal(t, 64, cap(cloner.ids)) // Not shrunk.
-	})
-
-	t.Run("should shrink expanded postings if length is < 70% capacity", func(t *testing.T) {
-		cloner := NewPostingsCloner(NewListPostings(make([]storage.SeriesRef, 33)))
-		assert.Equal(t, 33, len(cloner.ids))
-		assert.Equal(t, 33, cap(cloner.ids)) // Shrunk.
-	})
-}
-
 func TestFindIntersectingPostings(t *testing.T) {
 	t.Run("multiple intersections", func(t *testing.T) {
 		p := NewListPostings([]storage.SeriesRef{10, 15, 20, 25, 30, 35, 40, 45, 50})

tsdb/postings_for_matchers_cache.go

@@ -36,7 +36,7 @@ type IndexPostingsReader interface {
 
 // NewPostingsForMatchersCache creates a new PostingsForMatchersCache.
 // If `ttl` is 0, then it only deduplicates in-flight requests.
-// If `force` is true, then all requests go through cache, regardless of the `concurrent` param provided.
+// If `force` is true, then all requests go through cache, regardless of the `concurrent` param provided to the PostingsForMatchers method.
 func NewPostingsForMatchersCache(ttl time.Duration, maxItems int, maxBytes int64, force bool) *PostingsForMatchersCache {
 	b := &PostingsForMatchersCache{
 		calls:  &sync.Map{},
@@ -112,9 +112,9 @@ func (c *PostingsForMatchersCache) postingsForMatchersPromise(ctx context.Contex
 
 	// Estimate the size of the cache entry, in bytes. We use max() because
 	// size.Of() returns -1 if the value is nil.
-	estimatedSizeBytes := int64(len(key)) + max(0, int64(size.Of(outerErr))) + max(0, int64(size.Of(cloner)))
+	sizeBytes := int64(len(key)) + max(0, int64(size.Of(outerErr))) + max(0, int64(size.Of(cloner)))
 
-	c.created(key, c.timeNow(), estimatedSizeBytes)
+	c.created(key, c.timeNow(), sizeBytes)
 	return promise
 }
 
@@ -122,7 +122,7 @@ type postingsForMatchersCachedCall struct {
 	key string
 	ts  time.Time
 
-	// Size of he cached entry, in bytes.
+	// Size of the cached entry, in bytes.
 	sizeBytes int64
 }