pola-rs/polars · error

invalid value for POLARS_INFLIGHT_SINK_MORSEL_LIMIT: {x}

Error message

invalid value for POLARS_INFLIGHT_SINK_MORSEL_LIMIT: {x}

What it means

Panic from IOSinkNodeConfig::inflight_morsel_limit: the POLARS_INFLAT_SINK_MORSEL_LIMIT environment variable was set but could not be parsed as a NonZeroUsize (empty, non-numeric, or zero). The string {x} is the offending raw value.

Source

Thrown at crates/polars-stream/src/nodes/io_sinks/config.rs:33

const DEFAULT_PARTITIONED_UPLOAD_CHUNK_SIZE: NonZeroUsize =
    NonZeroUsize::new(6 * 1024 * 1024).unwrap();

pub struct IOSinkNodeConfig {
    pub file_format: FileWriteFormat,
    pub target: IOSinkTarget,
    pub unified_sink_args: UnifiedSinkArgs,
    pub input_schema: SchemaRef,
}

impl IOSinkNodeConfig {
    pub fn num_pipelines_per_sink(&self, num_pipelines: NonZeroUsize) -> NonZeroUsize {
        NonZeroUsize::min(num_pipelines, self.inflight_morsel_limit(num_pipelines))
    }

    pub fn inflight_morsel_limit(&self, num_pipelines: NonZeroUsize) -> NonZeroUsize {
        if let Ok(v) = std::env::var("POLARS_INFLIGHT_SINK_MORSEL_LIMIT").map(|x| {
            x.parse::<NonZeroUsize>().unwrap_or_else(|_| {
                panic!("invalid value for POLARS_INFLIGHT_SINK_MORSEL_LIMIT: {x}")
            })
        }) {
            return v;
        };

        NonZeroUsize::saturating_add(
            num_pipelines,
            // Additional buffer to accommodate head-of-line blocking
            4,
        )
    }

    pub fn max_open_sinks(&self) -> NonZeroUsize {
        if let Ok(v) = std::env::var("POLARS_MAX_OPEN_SINKS").map(|x| {
            x.parse::<NonZeroUsize>()
                .unwrap_or_else(|_| panic!("invalid value for POLARS_MAX_OPEN_SINKS: {x}"))
        }) {
            return v;

View on GitHub (pinned to 9b5d73fd00)

Solutions

1. Set POLARS_INFLIGHT_SINK_MORSEL_LIMIT to a positive integer, or unset it to use the default.

Example fix

export POLARS_INFLIGHT_SINK_MORSEL_LIMIT=16

When it happens

Trigger: Environment variable POLARS_INFLIGHT_SINK_MORSEL_LIMIT holds a non-numeric or out-of-range value.

Common situations: See trigger scenarios.

AI-assisted analysis of pola-rs/polars@9b5d73fd00 (2026-08-19). Data as JSON: /api/errors/e97708ae530a5ec5. Report an issue: GitHub.