From 9b9c3dce3ee10af5b6c4d070821bf47a861efd5b Mon Sep 17 00:00:00 2001
From: Alexey Andreev <ava1280@yandex.ru>
Date: Sat, 23 Jan 2021 00:11:17 +0300
Subject: [PATCH] feat(storage): add projection parameter for
 BucketHandle.Objects() (#3549)

Co-authored-by: Chris Cotter <cjcotter@google.com>
---
 storage/bucket.go           |  6 +++++-
 storage/integration_test.go | 37 +++++++++++++++++++++++++++++++++++++
 storage/storage.go          | 30 ++++++++++++++++++++++++++++++
 3 files changed, 72 insertions(+), 1 deletion(-)

diff --git a/storage/bucket.go b/storage/bucket.go
index 0d3be39eebc..7b1757b83de 100644
--- a/storage/bucket.go
+++ b/storage/bucket.go
@@ -1204,7 +1204,11 @@ func (it *ObjectIterator) Next() (*ObjectAttrs, error) {
 func (it *ObjectIterator) fetch(pageSize int, pageToken string) (string, error) {
 	req := it.bucket.c.raw.Objects.List(it.bucket.name)
 	setClientHeader(req.Header())
-	req.Projection("full")
+	projection := it.query.Projection
+	if projection == ProjectionDefault {
+		projection = ProjectionFull
+	}
+	req.Projection(projection.String())
 	req.Delimiter(it.query.Delimiter)
 	req.Prefix(it.query.Prefix)
 	req.StartOffset(it.query.StartOffset)
diff --git a/storage/integration_test.go b/storage/integration_test.go
index c21ff8430a0..788aa41e44e 100644
--- a/storage/integration_test.go
+++ b/storage/integration_test.go
@@ -698,6 +698,7 @@ func TestIntegration_Objects(t *testing.T) {
 	testObjectsIterateSelectedAttrs(t, bkt, objects)
 	testObjectsIterateAllSelectedAttrs(t, bkt, objects)
 	testObjectIteratorWithOffset(t, bkt, objects)
+	testObjectsIterateWithProjection(t, bkt)
 	t.Run("testObjectsIterateSelectedAttrsDelimiter", func(t *testing.T) {
 		query := &Query{Prefix: "", Delimiter: "/"}
 		if err := query.SetAttrSelection([]string{"Name"}); err != nil {
@@ -1236,6 +1237,42 @@ func testObjectsIterateAllSelectedAttrs(t *testing.T, bkt *BucketHandle, objects
 	}
 }
 
+func testObjectsIterateWithProjection(t *testing.T, bkt *BucketHandle) {
+	projections := map[Projection]bool{
+		ProjectionDefault: true,
+		ProjectionFull:    true,
+		ProjectionNoACL:   false,
+	}
+
+	for projection, expectACL := range projections {
+		query := &Query{Projection: projection}
+		it := bkt.Objects(context.Background(), query)
+		attrs, err := it.Next()
+		if err == iterator.Done {
+			t.Fatalf("iterator: no objects")
+		}
+		if err != nil {
+			t.Fatalf("iterator.Next: %v", err)
+		}
+
+		if expectACL {
+			if attrs.Owner == "" {
+				t.Errorf("projection %q: Owner is empty, want nonempty Owner", projection)
+			}
+			if len(attrs.ACL) == 0 {
+				t.Errorf("projection %q: ACL is empty, want at least one ACL rule", projection)
+			}
+		} else {
+			if attrs.Owner != "" {
+				t.Errorf("projection %q: got Owner = %q, want empty Owner", projection, attrs.Owner)
+			}
+			if len(attrs.ACL) != 0 {
+				t.Errorf("projection %q: got %d ACL rules, want empty ACL", projection, len(attrs.ACL))
+			}
+		}
+	}
+}
+
 func TestIntegration_SignedURL(t *testing.T) {
 	if testing.Short() { // do not test during replay
 		t.Skip("Integration tests skipped in short mode")
diff --git a/storage/storage.go b/storage/storage.go
index d4c25b83e0d..8852b9c6fc5 100644
--- a/storage/storage.go
+++ b/storage/storage.go
@@ -1306,6 +1306,31 @@ func encodeUint32(u uint32) string {
 	return base64.StdEncoding.EncodeToString(b)
 }
 
+// Projection is enumerated type for Query.Projection.
+type Projection int
+
+const (
+	// ProjectionDefault returns all fields of objects.
+	ProjectionDefault Projection = iota
+
+	// ProjectionFull returns all fields of objects.
+	ProjectionFull
+
+	// ProjectionNoACL returns all fields of objects except for Owner and ACL.
+	ProjectionNoACL
+)
+
+func (p Projection) String() string {
+	switch p {
+	case ProjectionFull:
+		return "full"
+	case ProjectionNoACL:
+		return "noAcl"
+	default:
+		return ""
+	}
+}
+
 // Query represents a query to filter objects from a bucket.
 type Query struct {
 	// Delimiter returns results in a directory-like fashion.
@@ -1341,6 +1366,11 @@ type Query struct {
 	// lexicographically before endOffset. If startOffset is also set, the objects
 	// listed will have names between startOffset (inclusive) and endOffset (exclusive).
 	EndOffset string
+
+	// Projection defines the set of properties to return. It will default to ProjectionFull,
+	// which returns all properties. Passing ProjectionNoACL will omit Owner and ACL,
+	// which may improve performance when listing many objects.
+	Projection Projection
 }
 
 // attrToFieldMap maps the field names of ObjectAttrs to the underlying field