[#1262] metabase: Do not allocate intermediate slices for indices

```
name              old alloc/op   new alloc/op   delta
Put/parallel-8       123kB ± 4%     119kB ± 3%  -2.72%  (p=0.006 n=10+9)
Put/sequential-8     170kB ± 1%     168kB ± 1%  -1.42%  (p=0.000 n=10+10)

name              old allocs/op  new allocs/op  delta
Put/parallel-8         473 ± 1%       469 ± 0%  -0.87%  (p=0.000 n=10+10)
Put/sequential-8       792 ± 0%       787 ± 0%  -0.58%  (p=0.000 n=10+10)
```

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

pkg/local_object_storage/metabase/delete.go

@@ -133,36 +133,19 @@ func (db *DB) deleteObject(
 	obj *objectSDK.Object,
 	isParent bool,
 ) error {
-	uniqueIndexes, err := delUniqueIndexes(obj, isParent)
+	err := delUniqueIndexes(tx, obj, isParent)
 	if err != nil {
-		return fmt.Errorf("can' build unique indexes: %w", err)
+		return fmt.Errorf("can't remove unique indexes")
 	}
 
-	// delete unique indexes
+	err = updateListIndexes(tx, obj, delListIndexItem)
-	for i := range uniqueIndexes {
-		delUniqueIndexItem(tx, uniqueIndexes[i])
-	}
-
-	// build list indexes
-	listIndexes, err := listIndexes(obj)
 	if err != nil {
-		return fmt.Errorf("can' build list indexes: %w", err)
+		return fmt.Errorf("can't remove list indexes: %w", err)
 	}
 
-	// delete list indexes
+	err = updateFKBTIndexes(tx, obj, delFKBTIndexItem)
-	for i := range listIndexes {
-		delListIndexItem(tx, listIndexes[i])
-	}
-
-	// build fake bucket tree indexes
-	fkbtIndexes, err := fkbtIndexes(obj)
 	if err != nil {
-		return fmt.Errorf("can' build fake bucket tree indexes: %w", err)
+		return fmt.Errorf("can't remove fake bucket tree indexes: %w", err)
-	}
-
-	// delete fkbt indexes
-	for i := range fkbtIndexes {
-		delFKBTIndexItem(tx, fkbtIndexes[i])
 	}
 
 	return nil
@@ -190,29 +173,30 @@ func delUniqueIndexItem(tx *bbolt.Tx, item namedBucketItem) {
 	}
 }
 
-func delFKBTIndexItem(tx *bbolt.Tx, item namedBucketItem) {
+func delFKBTIndexItem(tx *bbolt.Tx, item namedBucketItem) error {
 	bkt := tx.Bucket(item.name)
 	if bkt == nil {
-		return
+		return nil
 	}
 
 	fkbtRoot := bkt.Bucket(item.key)
 	if fkbtRoot == nil {
-		return
+		return nil
 	}
 
 	_ = fkbtRoot.Delete(item.val) // ignore error, best effort there
+	return nil
 }
 
-func delListIndexItem(tx *bbolt.Tx, item namedBucketItem) {
+func delListIndexItem(tx *bbolt.Tx, item namedBucketItem) error {
 	bkt := tx.Bucket(item.name)
 	if bkt == nil {
-		return
+		return nil
 	}
 
 	lst, err := decodeList(bkt.Get(item.key))
 	if err != nil || len(lst) == 0 {
-		return
+		return nil
 	}
 
 	// remove element from the list
@@ -228,25 +212,24 @@ func delListIndexItem(tx *bbolt.Tx, item namedBucketItem) {
 	if len(newLst) == 0 {
 		_ = bkt.Delete(item.key) // ignore error, best effort there
 
-		return
+		return nil
 	}
 
 	// if list is not empty, then update it
 	encodedLst, err := encodeList(lst)
 	if err != nil {
-		return // ignore error, best effort there
+		return nil // ignore error, best effort there
 	}
 
 	_ = bkt.Put(item.key, encodedLst) // ignore error, best effort there
+	return nil
 }
 
-func delUniqueIndexes(obj *objectSDK.Object, isParent bool) ([]namedBucketItem, error) {
+func delUniqueIndexes(tx *bbolt.Tx, obj *objectSDK.Object, isParent bool) error {
 	addr := object.AddressOf(obj)
 	objKey := objectKey(addr.ObjectID())
 	addrKey := addressKey(addr)
 
-	result := make([]namedBucketItem, 0, 5)
-
 	// add value to primary unique bucket
 	if !isParent {
 		var bucketName []byte
@@ -261,34 +244,32 @@ func delUniqueIndexes(obj *objectSDK.Object, isParent bool) ([]namedBucketItem,
 		case objectSDK.TypeLock:
 			bucketName = bucketNameLockers(*addr.ContainerID())
 		default:
-			return nil, ErrUnknownObjectType
+			return ErrUnknownObjectType
 		}
 
-		result = append(result, namedBucketItem{
+		delUniqueIndexItem(tx, namedBucketItem{
 			name: bucketName,
 			key:  objKey,
 		})
 	} else {
-		result = append(result, namedBucketItem{
+		delUniqueIndexItem(tx, namedBucketItem{
 			name: parentBucketName(obj.ContainerID()),
 			key:  objKey,
 		})
 	}
 
-	result = append(result,
+	delUniqueIndexItem(tx, namedBucketItem{ // remove from small blobovnicza id index
-		namedBucketItem{ // remove from small blobovnicza id index
 		name: smallBucketName(addr.ContainerID()),
 		key:  objKey,
-		},
+	})
-		namedBucketItem{ // remove from root index
+	delUniqueIndexItem(tx, namedBucketItem{ // remove from root index
 		name: rootBucketName(addr.ContainerID()),
 		key:  objKey,
-		},
+	})
-		namedBucketItem{ // remove from ToMoveIt index
+	delUniqueIndexItem(tx, namedBucketItem{ // remove from ToMoveIt index
 		name: toMoveItBucketName,
 		key:  addrKey,
-		},
+	})
-	)
 
-	return result, nil
+	return nil
 }

pkg/local_object_storage/metabase/put.go

@@ -129,46 +129,19 @@ func (db *DB) put(tx *bbolt.Tx, obj *objectSDK.Object, id *blobovnicza.ID, si *o
 		}
 	}
 
-	// build unique indexes
+	err = putUniqueIndexes(tx, obj, si, id)
-	uniqueIndexes, err := uniqueIndexes(obj, si, id)
 	if err != nil {
-		return fmt.Errorf("can' build unique indexes: %w", err)
+		return fmt.Errorf("can't put unique indexes: %w", err)
 	}
 
-	// put unique indexes
+	err = updateListIndexes(tx, obj, putListIndexItem)
-	for i := range uniqueIndexes {
-		err = putUniqueIndexItem(tx, uniqueIndexes[i])
 	if err != nil {
-			return err
+		return fmt.Errorf("can't put list indexes: %w", err)
-		}
 	}
 
-	// build list indexes
+	err = updateFKBTIndexes(tx, obj, putFKBTIndexItem)
-	listIndexes, err := listIndexes(obj)
 	if err != nil {
-		return fmt.Errorf("can' build list indexes: %w", err)
+		return fmt.Errorf("can't put fake bucket tree indexes: %w", err)
-	}
-
-	// put list indexes
-	for i := range listIndexes {
-		err = putListIndexItem(tx, listIndexes[i])
-		if err != nil {
-			return err
-		}
-	}
-
-	// build fake bucket tree indexes
-	fkbtIndexes, err := fkbtIndexes(obj)
-	if err != nil {
-		return fmt.Errorf("can' build fake bucket tree indexes: %w", err)
-	}
-
-	// put fake bucket tree indexes
-	for i := range fkbtIndexes {
-		err = putFKBTIndexItem(tx, fkbtIndexes[i])
-		if err != nil {
-			return err
-		}
 	}
 
 	// update container volume size estimation
@@ -187,12 +160,15 @@ func (db *DB) put(tx *bbolt.Tx, obj *objectSDK.Object, id *blobovnicza.ID, si *o
 	return nil
 }
 
-// builds list of <unique> indexes from the object.
+func putUniqueIndexes(
-func uniqueIndexes(obj *objectSDK.Object, si *objectSDK.SplitInfo, id *blobovnicza.ID) ([]namedBucketItem, error) {
+	tx *bbolt.Tx,
+	obj *objectSDK.Object,
+	si *objectSDK.SplitInfo,
+	id *blobovnicza.ID,
+) error {
 	isParent := si != nil
 	addr := object.AddressOf(obj)
 	objKey := objectKey(addr.ObjectID())
-	result := make([]namedBucketItem, 0, 3)
 
 	// add value to primary unique bucket
 	if !isParent {
@@ -208,27 +184,33 @@ func uniqueIndexes(obj *objectSDK.Object, si *objectSDK.SplitInfo, id *blobovnic
 		case objectSDK.TypeLock:
 			bucketName = bucketNameLockers(*addr.ContainerID())
 		default:
-			return nil, ErrUnknownObjectType
+			return ErrUnknownObjectType
 		}
 
 		rawObject, err := obj.CutPayload().Marshal()
 		if err != nil {
-			return nil, fmt.Errorf("can't marshal object header: %w", err)
+			return fmt.Errorf("can't marshal object header: %w", err)
 		}
 
-		result = append(result, namedBucketItem{
+		err = putUniqueIndexItem(tx, namedBucketItem{
 			name: bucketName,
 			key:  objKey,
 			val:  rawObject,
 		})
+		if err != nil {
+			return err
+		}
 
 		// index blobovniczaID if it is present
 		if id != nil {
-			result = append(result, namedBucketItem{
+			err = putUniqueIndexItem(tx, namedBucketItem{
 				name: smallBucketName(addr.ContainerID()),
 				key:  objKey,
 				val:  *id,
 			})
+			if err != nil {
+				return err
+			}
 		}
 	}
 
@@ -242,79 +224,94 @@ func uniqueIndexes(obj *objectSDK.Object, si *objectSDK.SplitInfo, id *blobovnic
 		if isParent {
 			splitInfo, err = si.Marshal()
 			if err != nil {
-				return nil, fmt.Errorf("can't marshal split info: %w", err)
+				return fmt.Errorf("can't marshal split info: %w", err)
 			}
 		}
 
-		result = append(result, namedBucketItem{
+		err = putUniqueIndexItem(tx, namedBucketItem{
 			name: rootBucketName(addr.ContainerID()),
 			key:  objKey,
 			val:  splitInfo,
 		})
+		if err != nil {
+			return err
+		}
 	}
 
-	return result, nil
+	return nil
 }
 
-// builds list of <list> indexes from the object.
+type updateIndexItemFunc = func(tx *bbolt.Tx, item namedBucketItem) error
-func listIndexes(obj *objectSDK.Object) ([]namedBucketItem, error) {
+
-	result := make([]namedBucketItem, 0, 3)
+func updateListIndexes(tx *bbolt.Tx, obj *objectSDK.Object, f updateIndexItemFunc) error {
 	addr := object.AddressOf(obj)
 	objKey := objectKey(addr.ObjectID())
 
 	// index payload hashes
-	result = append(result, namedBucketItem{
+	err := f(tx, namedBucketItem{
 		name: payloadHashBucketName(addr.ContainerID()),
 		key:  obj.PayloadChecksum().Sum(),
 		val:  objKey,
 	})
+	if err != nil {
+		return err
+	}
 
 	// index parent ids
 	if obj.ParentID() != nil {
-		result = append(result, namedBucketItem{
+		err := f(tx, namedBucketItem{
 			name: parentBucketName(addr.ContainerID()),
 			key:  objectKey(obj.ParentID()),
 			val:  objKey,
 		})
+		if err != nil {
+			return err
+		}
 	}
 
 	// index split ids
 	if obj.SplitID() != nil {
-		result = append(result, namedBucketItem{
+		err := f(tx, namedBucketItem{
 			name: splitBucketName(addr.ContainerID()),
 			key:  obj.SplitID().ToV2(),
 			val:  objKey,
 		})
+		if err != nil {
+			return err
+		}
 	}
 
-	return result, nil
+	return nil
 }
 
-// builds list of <fake bucket tree> indexes from the object.
+func updateFKBTIndexes(tx *bbolt.Tx, obj *objectSDK.Object, f updateIndexItemFunc) error {
-func fkbtIndexes(obj *objectSDK.Object) ([]namedBucketItem, error) {
 	addr := object.AddressOf(obj)
 	objKey := []byte(addr.ObjectID().String())
 
 	attrs := obj.Attributes()
-	result := make([]namedBucketItem, 0, 1+len(attrs))
 
-	// owner
+	err := f(tx, namedBucketItem{
-	result = append(result, namedBucketItem{
 		name: ownerBucketName(addr.ContainerID()),
 		key:  []byte(obj.OwnerID().String()),
 		val:  objKey,
 	})
+	if err != nil {
+		return err
+	}
 
 	// user specified attributes
 	for i := range attrs {
-		result = append(result, namedBucketItem{
+		err := f(tx, namedBucketItem{
 			name: attributeBucketName(addr.ContainerID(), attrs[i].Key()),
 			key:  []byte(attrs[i].Value()),
 			val:  objKey,
 		})
+		if err != nil {
+			return err
+		}
 	}
 
-	return result, nil
+	return nil
 }
 
 func putUniqueIndexItem(tx *bbolt.Tx, item namedBucketItem) error {