pola-rs/polars · error

failed to serialize the schema

Error message

failed to serialize the schema

What it means

Expect panic converting a $defs entry into a schemars Schema while computing schema hashes: the definition object did not match Schema's expected shape. It guards the (name, def) conversion inside the DslPlan definitions loop of the dsl-schema hash tooling.

Source

Thrown at crates/polars-plan/src/bin/dsl-schema.rs:136

                for (name, def) in definitions {
                    let mut def = def.to_owned();
                    def.sort_all_objects();
                    let schema: &Schema = (&def).try_into().unwrap();
                    hashes.insert(name.into(), schema_hash(schema).into());
                }

                assert!(definitions.contains_key("DslPlan"));
            }
        }

        hashes.sort_keys();

        serde_json::to_string_pretty(&hashes).expect("failed to serialize schema hashes file")
    }

    fn schema_hash(schema: &Schema) -> String {
        let mut digest = digest_io::IoWrapper(sha2::Sha256::new());
        serde_json::to_writer(&mut digest, schema).expect("failed to serialize the schema");
        let hash = digest.0.finalize();
        hex::encode(hash)
    }
}

View on GitHub (pinned to 9b5d73fd00)

Solutions

1. Serialization of the DSL schema failed; ensure the plan contains only serializable nodes.
2. Update the tool/library versions so the schema format matches.

When it happens

Trigger: This panic/expect fires when execution reaches an unguarded state described by: "failed to serialize the schema". 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 ("failed to serialize the schema"). 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/2c8ba0704cc989a1. Report an issue: GitHub.