satellite/metainfo: reduce database hits for segment creation

Change-Id: I48a748b48daefa95f1dfbf6a0d75e65a568ee36a

satellite/metabase/commit.go

@@ -224,6 +224,8 @@ type BeginSegment struct {
 	RootPieceID storj.PieceID
 
 	Pieces Pieces
+
+	ObjectExistsChecked bool
 }
 
 // BeginSegment verifies, whether a new segment upload can be started.
@@ -242,24 +244,27 @@ func (db *DB) BeginSegment(ctx context.Context, opts BeginSegment) (err error) {
 		return ErrInvalidRequest.New("RootPieceID missing")
 	}
 
-	// NOTE: this isn't strictly necessary, since we can also fail this in CommitSegment.
-	//       however, we should prevent creating segements for non-partial objects.
+	if !opts.ObjectExistsChecked {
+		// NOTE: Find a way to safely remove this. This isn't strictly necessary,
+		// since we can also fail this in CommitSegment.
+		// We should prevent creating segements for non-partial objects.
 
-	// Verify that object exists and is partial.
-	var exists bool
-	err = db.db.QueryRowContext(ctx, `
+		// Verify that object exists and is partial.
+		var exists bool
+		err = db.db.QueryRowContext(ctx, `
 		SELECT EXISTS (
 			SELECT 1
 			FROM objects
 			WHERE (project_id, bucket_name, object_key, version, stream_id) = ($1, $2, $3, $4, $5) AND
 				status = `+statusPending+`
 		)`,
-		opts.ProjectID, []byte(opts.BucketName), opts.ObjectKey, opts.Version, opts.StreamID).Scan(&exists)
-	if err != nil {
-		return Error.New("unable to query object status: %w", err)
-	}
-	if !exists {
-		return ErrPendingObjectMissing.New("")
+			opts.ProjectID, []byte(opts.BucketName), opts.ObjectKey, opts.Version, opts.StreamID).Scan(&exists)
+		if err != nil {
+			return Error.New("unable to query object status: %w", err)
+		}
+		if !exists {
+			return ErrPendingObjectMissing.New("")
+		}
 	}
 
 	mon.Meter("segment_begin").Mark(1)

satellite/metainfo/batch.go

@@ -226,11 +226,13 @@ func (endpoint *Endpoint) Batch(ctx context.Context, req *pb.BatchRequest) (resp
 		case *pb.BatchRequestItem_SegmentBegin:
 			singleRequest.SegmentBegin.Header = req.Header
 
+			justCreatedObject := false
 			if singleRequest.SegmentBegin.StreamId.IsZero() && !lastStreamID.IsZero() {
 				singleRequest.SegmentBegin.StreamId = lastStreamID
+				justCreatedObject = true
 			}
 
-			response, err := endpoint.BeginSegment(ctx, singleRequest.SegmentBegin)
+			response, err := endpoint.beginSegment(ctx, singleRequest.SegmentBegin, justCreatedObject)
 			if err != nil {
 				return resp, err
 			}

satellite/metainfo/endpoint_segment.go

@@ -31,6 +31,11 @@ func calculateSpaceUsed(segmentSize int64, numberOfPieces int, rs storj.Redundan
 // BeginSegment begins segment uploading.
 func (endpoint *Endpoint) BeginSegment(ctx context.Context, req *pb.SegmentBeginRequest) (resp *pb.SegmentBeginResponse, err error) {
 	defer mon.Task()(&ctx)(&err)
+	return endpoint.beginSegment(ctx, req, false)
+}
+
+func (endpoint *Endpoint) beginSegment(ctx context.Context, req *pb.SegmentBeginRequest, objectJustCreated bool) (resp *pb.SegmentBeginResponse, err error) {
+	defer mon.Task()(&ctx)(&err)
 
 	endpoint.versionCollector.collect(req.Header.UserAgent, mon.Func().ShortName())
 
@@ -121,8 +126,9 @@ func (endpoint *Endpoint) BeginSegment(ctx context.Context, req *pb.SegmentBegin
 			Part:  uint32(req.Position.PartNumber),
 			Index: uint32(req.Position.Index),
 		},
-		RootPieceID: rootPieceID,
-		Pieces:      pieces,
+		RootPieceID:         rootPieceID,
+		Pieces:              pieces,
+		ObjectExistsChecked: objectJustCreated,
 	})
 	if err != nil {
 		return nil, endpoint.convertMetabaseErr(err)