pola-rs/polars · error

The batch is not available

Error message

The batch is not available

What it means

Documented panic of StreamState::unwrap in the IPC stream reader: unwrap was called while the state was Waiting, i.e. the stream produced no batch for this iteration (e.g. an empty or exhausted message). Callers should match on StreamState::Some/Waiting instead of unwrapping.

Source

Thrown at crates/polars-arrow/src/io/ipc/read/stream.rs:83

/// just doesn't hold any data right now.
pub enum StreamState {
    /// A live stream without data
    Waiting,
    /// Next item in the stream
    Some(RecordBatchT<Box<dyn Array>>),
}

impl StreamState {
    /// Return the data inside this wrapper.
    ///
    /// # Panics
    ///
    /// If the `StreamState` was `Waiting`.
    pub fn unwrap(self) -> RecordBatchT<Box<dyn Array>> {
        if let StreamState::Some(batch) = self {
            batch
        } else {
            panic!("The batch is not available")
        }
    }
}

/// Reads the next item, yielding `None` if the stream is done,
/// and a [`StreamState`] otherwise.
fn read_next<R: Read + Seek>(
    reader: &mut R,
    metadata: &StreamMetadata,
    dictionaries: &mut Dictionaries,
    message_buffer: &mut Vec<u8>,
    projection: &Option<ProjectionInfo>,
    scratch: &mut Vec<u8>,
    checked: UnsafeBool,
) -> PolarsResult<Option<StreamState>> {
    // determine metadata length
    let mut meta_length: [u8; 4] = [0; 4];

View on GitHub (pinned to 9b5d73fd00)

Solutions

1. Poll the stream again later: the batch is produced asynchronously and is not ready yet.
2. Check whether the stream has finished or errored before requesting the next batch.

When it happens

Trigger: This panic/expect fires when execution reaches an unguarded state described by: "The batch is not available". Typical triggers: unsupported dtype or feature-gated code path reached at runtime, invalid user input or environment variable value, calling API methods in the wrong order or on mismatched types, or data (lengths, offsets, ranges) violating the function's preconditions.

Common situations: Encountered when input data or configuration does not meet the preconditions of the throwing code path ("The batch is not available"). Common cases: missing Cargo feature flags, mismatched dtypes/lengths between arrays or series, out-of-range temporal values, malformed environment variables, or operations on unsupported/complex nested types.

AI-assisted analysis of pola-rs/polars@9b5d73fd00 (2026-08-19). Data as JSON: /api/errors/02be06999d5545fd. Report an issue: GitHub.