apache/beam · error

bad iterable/stream: %+v

Error message

bad iterable/stream: %+v

What it means

DecodeCoderRef converts stream-type refs (iterables) back into coders. A stream ref must have exactly one component (the element coder); any other count is malformed, so decoding fails with the ref printed in the message.

Solutions

1. Regenerate the pipeline artifact from the original pipeline so stream coders are re-encoded correctly.
2. Match SDK versions between the encoder and decoder of the pipeline graph.
3. Check custom graph-mutation passes for edits to stream/iterable coder component lists.
4. Inspect the printed CoderRef to trace which transform's coder is malformed.

Example fix

// before
ref := &graphx.CoderRef{Type: graphx.Stream, Components: nil}
c, err := graphx.DecodeCoderRef(ref)

// after
ref := &graphx.CoderRef{Type: graphx.Stream, Components: []*graphx.CoderRef{elemRef}}
c, err := graphx.DecodeCoderRef(ref)

func validStreamRef(r *graphx.CoderRef) bool {
	return r != nil && r.Type == graphx.Stream && len(r.Components) == 1
}

func isStreamRef(r *graphx.CoderRef) bool { return r != nil && r.Type == graphx.Stream && len(r.Components) == 1 }

c, err := graphx.DecodeCoderRef(ref)
if err != nil {
	if strings.Contains(err.Error(), "bad iterable/stream") {
		return nil, fmt.Errorf("stream ref needs exactly 1 element component %v: %w", ref, err)
	}
	return nil, err
}

When it happens

Trigger: Decoding a CoderRef with Type streamType whose Components has length != 1 — during deserialization of a pipeline graph or job description containing a corrupted or foreign-encoded iterable coder.

Common situations: Pipeline artifacts produced by different SDK versions; custom graph rewriters duplicating element components; truncated or hand-edited proto/json pipelines; GBK output graphs decoded with mismatched tooling.

Related errors

• bad length prefix: %+v
• bad nullable: %+v
• bad pair: %+v
• bad windowed value: %+v
• len mismatch decoding a

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/f1921aef0786b42f. Report an issue: GitHub.

Appendix: source

Thrown at sdks/go/pkg/beam/core/runtime/graphx/dataflow.go:333

		if len(c.Components) != 2 {
			return nil, errors.Errorf("bad windowed value: %+v", c)
		}

		elm, err := DecodeCoderRef(c.Components[0])
		if err != nil {
			return nil, err
		}
		w, err := decodeWindowCoder(c.Components[1])
		if err != nil {
			return nil, err
		}
		t := typex.New(typex.WindowedValueType, elm.T)

		return &coder.Coder{Kind: coder.WindowedValue, T: t, Components: []*coder.Coder{elm}, Window: w}, nil

	case streamType:
		if len(c.Components) != 1 {
			return nil, errors.Errorf("bad iterable/stream: %+v", c)
		}

		inner, err := DecodeCoderRef(c.Components[0])
		if err != nil {
			return nil, err
		}

		t := typex.New(reflect.SliceOf(inner.T.Type()), inner.T)
		return &coder.Coder{Kind: coder.Iterable, T: t, Components: []*coder.Coder{inner}}, nil

	case rowType:
		subC := c.Components[0]
		schm := &pipepb.Schema{}
		if err := protox.DecodeBase64(subC.Type, schm); err != nil {
			return nil, err
		}
		t, err := schema.ToType(schm)
		if err != nil {

View on GitHub (pinned to 12126d8942)