risingwavelabs/risingwave · error · ArrayError

Failed to decode prost: field not found `{}`

Error message

Failed to decode prost: field not found `{}`

What it means

This error is thrown when converting a `PbFieldNotFound` protobuf decoding error into an `ArrayError`. It means a serialized array's protobuf representation is missing a field the Rust array type requires during deserialization (e.g. a null bitmap or data buffer). It indicates the incoming protobuf bytes do not match the expected array schema.

Source

Thrown at src/common/src/array/error.rs:56

    #[error("Convert from arrow error: {0}")]
    FromArrow(
        #[source]
        #[backtrace]
        BoxedError,
    ),

    #[error("Convert to arrow error: {0}")]
    ToArrow(
        #[source]
        #[backtrace]
        BoxedError,
    ),
}

impl From<PbFieldNotFound> for ArrayError {
    fn from(err: PbFieldNotFound) -> Self {
        anyhow!("Failed to decode prost: field not found `{}`", err.0).into()
    }
}

impl From<Infallible> for ArrayError {
    fn from(err: Infallible) -> Self {
        unreachable!("Infallible error: {:?}", err)
    }
}

impl ArrayError {
    pub fn internal(msg: impl ToString) -> Self {
        ArrayError::Internal(anyhow!(msg.to_string()))
    }
}

View on GitHub (pinned to 6469eb736d)

Solutions

1. Verify the protobuf payload was produced by a matching RisingWave version / schema (check `prost` generated definitions).
2. Inspect the `PbArray` before decoding: ensure `null_bitmap` and required `values`/`body` fields are populated.
3. Check for version skew between the component that serialized the array (e.g. meta/storage) and the one deserializing it.
4. If decoding optional legacy data, handle the `PbFieldNotFound` case explicitly instead of relying on the blanket From impl.

Example fix

// before: decoding may panic/error on missing field
let arr = ArrayImpl::from_protobuf(&pb_array, cardinality)?;
// after: pre-validate required fields
ensure!(!pb_array.values.is_empty(), "array must have body buffer");
ensure!(pb_array.null_bitmap.is_some(), "array must have null bitmap");
let arr = ArrayImpl::from_protobuf(&pb_array, cardinality)?;

fn valid_pb_array(a: &PbArray) -> bool {
    a.null_bitmap.is_some() && !a.values.is_empty()
}

fn is_decodable(a: &PbArray) -> bool { a.null_bitmap.is_some() }

match ArrayImpl::from_protobuf(&pb, card) {
    Ok(arr) => arr,
    Err(e) if e.to_string().contains("field not found") => fallback_decode_legacy(&pb)?,
    Err(e) => return Err(e.into()),
}

When it happens

Trigger: Calling `ArrayImpl::from_protobuf` (or any array-type-specific `from_protobuf`) on a `PbArray` where a required field such as `null_bitmap` or `body` is absent, so `get_null_bitmap()`/`get_*` returns `PbFieldNotFound`, which is converted via `From<PbFieldNotFound> for ArrayError`.

Common situations: Version skew between writer and reader where the protobuf schema changed; hand-crafted or corrupted protobuf payloads; deserializing an array written by a different array type or an old RisingWave version.

Understand the failure class

Background: "cannot parse invalid wire-format data", "cannot unmarshal", "failed unmarshalling": protobuf unmarshal errors explained — this error's family across 10 libraries.

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• Must have exactly 1 buffer in a jsonb array
• Must have no buffer in a list array
• Must have at least one element in offsets
• Invalid list encoding: {0}
• unspecified type of `WindowFrame`

AI-assisted analysis of risingwavelabs/risingwave@6469eb736d (2026-09-11). Data as JSON: /api/errors/169ba54a95445ad9. Report an issue: GitHub.