pola-rs/polars · error

Arrow datatype {dt:?} not supported by Polars. You probably

Error message

Arrow datatype {dt:?} not supported by Polars. You probably need to activate that data-type feature.

What it means

The catch-all arm of DataType::from_arrow: an Arrow datatype with no polars mapping (typically one gated behind a disabled data-type feature) reaches this panic naming the Arrow dtype. Rebuild polars with the relevant dtype feature or filter the column out before reading.

Source

Thrown at crates/polars-core/src/datatypes/field.rs:315

            ArrowDataType::LargeBinary | ArrowDataType::Binary => DataType::Binary,
            ArrowDataType::FixedSizeBinary(_) => DataType::Binary,
            ArrowDataType::Map(inner, _keys_sorted) => {
                let entries = Self::from_arrow_field(inner);
                #[cfg(feature = "dtype-map")]
                let map = entries.map_from_positional_entries_dtype();
                #[cfg(not(feature = "dtype-map"))]
                let map: Option<DataType> = None;
                map.unwrap_or_else(|| DataType::List(entries.boxed()))
            },
            ArrowDataType::Interval(IntervalUnit::MonthDayNano) => {
                check_allow_importing_interval_as_struct("month_day_nano_interval").unwrap();
                feature_gated!("dtype-struct", DataType::_month_days_ns_struct_type())
            },
            ArrowDataType::Interval(IntervalUnit::MonthDayMillis) => {
                check_allow_importing_interval_as_struct("month_day_millisecond_interval").unwrap();
                feature_gated!("dtype-struct", DataType::_month_days_ns_struct_type())
            },
            dt => panic!(
                "Arrow datatype {dt:?} not supported by Polars. \
                You probably need to activate that data-type feature."
            ),
        }
    }
}

impl From<&ArrowField> for Field {
    fn from(f: &ArrowField) -> Self {
        Field::new(f.name.clone(), DataType::from_arrow_field(f))
    }
}

View on GitHub (pinned to 68506541d2)

Solutions

1. Activate the cargo feature matching the Arrow data type (e.g. `dtype-array`, `dtype-struct`, `dtype-categorical`, `dtype-decimal`).
2. Check the polars crate's feature list and enable the `dtype-*` feature for the reported type.

When it happens

Trigger: This panic/expect fires when execution reaches an unguarded state described by: "Arrow datatype {dt:?} not supported by Polars. You probably need to activate that data-type feature.". 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 ("Arrow datatype {dt:?} not supported by Polars. You probably need to activate that data-type feature."). 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@68506541d2 (2026-08-19). Data as JSON: /api/errors/bf0649619f51fb55. Report an issue: GitHub.