apache/cassandra · error · MarshalException

Not enough bytes to read a vector<

Error message

Not enough bytes to read a vector<%s, %d>

What it means

VectorType's unpack reads 'dimension' fixed-length elements from the buffer; if fewer bytes remain than one element's fixed length for any element, it throws this MarshalException. The serialized form of a fixed-length vector must contain exactly dimension elements of elementSize bytes each.

Solutions

1. Verify the input buffer size equals or exceeds dimension * elementType.valueLengthIfFixed() before unpacking
2. Confirm the vector column dimension matches the data as written (did not change since write)
3. Scrub/repair affected SSTables if storage data is truncated; restore from backup if corruption is confirmed

Example fix

// before
if (buffer.remaining() < dimension * elementSize) throw new IllegalArgumentException("truncated vector");
vectorType.unpack(buffer);
// after
int elementSize = elementType.valueLengthIfFixed();
if (buffer.remaining() < dimension * elementSize) throw new IllegalArgumentException("truncated vector");
vectorType.unpack(buffer);

if (buffer.remaining() < dimension * elementType.valueLengthIfFixed()) throw new IllegalArgumentException("truncated vector payload");

try { vectorType.unpack(buffer); } catch (MarshalException e) { log.error("cannot unpack vector: {}", e.getMessage()); return null; }

When it happens

Trigger: unpack called on a buffer shorter than dimension * elementLength (elementLength > 0, i.e. fixed-length element types like int/float); truncated values from storage or network; dimension increased in schema while old data remains short.

Common situations: Truncated SSTable/commit-log data; schema dimension mismatch after ALTER of vector dimension; hand-crafted buffers in tests; partial reads from a custom transport.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• Invalid empty vector value
• Not enough bytes to read a + getCollectionName()
• Not enough bytes to read a
• Unexpected extraneous bytes after value
• Attempted to add float vector of dimension

AI-assisted analysis of apache/cassandra@88fd0f6a0e (2026-09-10). Data as JSON: /api/errors/011cd5507b6b6b24. Report an issue: GitHub.

Appendix: source

Thrown at src/java/org/apache/cassandra/db/marshal/VectorType.java:474

                    return rc;

                offset += elementLength;
            }
            return 0;
        }

        @Override
        public <V> List<V> unpack(V buffer, ValueAccessor<V> accessor)
        {
            if (isNull(buffer, accessor))
                return null;
            List<V> result = new ArrayList<>(dimension);
            int offset = 0;
            int elementLength = elementType.valueLengthIfFixed();
            for (int i = 0; i < dimension; i++)
            {
                if (accessor.sizeFromOffset(buffer, offset) < elementLength)
                    throw new MarshalException(String.format("Not enough bytes to read a vector<%s, %d>", elementType.asCQL3Type(), dimension));

                V bb = accessor.slice(buffer, offset, elementLength);
                offset += elementLength;
                elementSerializer.validate(bb, accessor);
                result.add(bb);
            }
            checkConsumedFully(buffer, accessor, offset);

            return result;
        }

        @Override
        public <V> V pack(List<V> value, ValueAccessor<V> accessor)
        {
            if (value == null)
                rejectNullOrEmptyValue();

            check(value);

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