pola-rs/polars · error

no valid schema can be derived for the query

Error message

no valid schema can be derived for the query

What it means

Internal expect() in the IR builder (with_columns): expr_irs_to_schema failed to derive output names/dtypes for the new expression list against the input schema, so the horizontally-extended schema cannot be constructed. Usually means one of the with_columns expressions resolves to an invalid/unknown dtype.

Source

Thrown at crates/polars-plan/src/plans/builder_ir.rs:215

    pub fn build(self) -> IR {
        if self.root.0 == self.lp_arena.len() {
            self.lp_arena.pop().unwrap()
        } else {
            self.lp_arena.take(self.root)
        }
    }

    pub fn schema(&'a self) -> Cow<'a, SchemaRef> {
        self.lp_arena.get(self.root).schema(self.lp_arena)
    }

    pub fn with_columns(self, exprs: Vec<ExprIR>, options: ProjectionOptions) -> Self {
        let schema = self.schema();
        let mut new_schema = (**schema).clone();

        let hstack_schema = expr_irs_to_schema(&exprs, &schema, self.expr_arena)
            .expect("no valid schema can be derived for the query");
        new_schema.merge(hstack_schema);

        let lp = IR::HStack {
            input: self.root,
            exprs,
            schema: Arc::new(new_schema),
            options,
        };
        self.add_alp(lp)
    }

    pub fn with_columns_simple<I, J: Into<Node>>(self, exprs: I, options: ProjectionOptions) -> Self
    where
        I: IntoIterator<Item = J>,
    {
        let schema = self.schema();
        let mut new_schema = (**schema).clone();

View on GitHub (pinned to 5d8ebabf11)

Solutions

1. The query does not produce a derivable schema; ensure all input columns and expressions resolve to known dtypes.
2. Simplify or annotate the query (e.g. explicit casts) so the schema can be inferred.

When it happens

Trigger: This panic/expect fires when execution reaches an unguarded state described by: "no valid schema can be derived for the query". 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 ("no valid schema can be derived for the query"). 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@5d8ebabf11 (2026-08-19). Data as JSON: /api/errors/8e48070ce5b9f637. Report an issue: GitHub.