databendlabs/databend · error

internal error: entered unreachable code

Error message

internal error: entered unreachable code

What it means

When building a bloom index for a Map column, the code downcasts the inner column and expects the inner type to be a Tuple (the key/value pair struct of the map). If the declared inner type is anything else, the `let ... else` guard hits `unreachable!()`, producing internal error 1001 during index generation (CREATE TABLE ... with bloom index or index build).

Solutions

1. Drop and rebuild the bloom index so it is regenerated against the current schema
2. Verify the map column schema (`DESC table`) shows Map(Tuple(k,v)) and re-create the table/migrate data if not
3. Report as a bug with schema and version: the guard should return an internal error with the type name instead of unreachable!()

Example fix

// before
let DataType::Tuple(kv_tys) = inner_ty else {
    unreachable!();
};
// after
let DataType::Tuple(kv_tys) = inner_ty else {
    return Err(ErrorCode::Internal(format!(
        "expect map inner tuple, got {:?}", inner_ty)));
};

-- verify map column layout before creating bloom index
DESC <table>;
-- expect Map(Tuple(String, T)); if inner is not Tuple, fix schema first

try {
  createTableWithBloomIndex();
} catch (e) {
  if (e.code === 1001) {
    // drop the index, verify schema with DESC, rebuild index
  }
}

When it happens

Trigger: Building a bloom index on a MAP column whose inner type metadata is not Tuple(k,v) — i.e. schema/type metadata inconsistent with the stored column layout (e.g. Variant-typed map values mis-declared, or schema drift after engine changes).

Common situations: Tables created/altered with MAP under one Databend version and indexed under another; custom ingest paths writing mismatched schema metadata.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

• internal error: entered unreachable code
• invalid map type
• internal error: entered unreachable code
• internal error: entered unreachable code
• internal error: entered unreachable code

AI-assisted analysis of databendlabs/databend@288d84d76e (2026-09-11). Data as JSON: /api/errors/4463127a9b382c8e. Report an issue: GitHub.

Appendix: source

Thrown at src/query/storages/common/index/src/bloom_index.rs:988

                .get_by_offset(index_column.index)
                .value()
                .convert_to_full_column(field_type, 1);

            let (column, data_type) = match field_type.remove_nullable() {
                DataType::Map(box inner_ty) => {
                    // Add bloom filter for the value of map type
                    let map_column = if field_type.is_nullable() {
                        let nullable_column =
                            NullableType::<MapType<AnyType, AnyType>>::try_downcast_column(&column)
                                .unwrap();
                        nullable_column.column
                    } else {
                        MapType::<AnyType, AnyType>::try_downcast_column(&column).unwrap()
                    };
                    let column = map_column.underlying_column().values;

                    let DataType::Tuple(kv_tys) = inner_ty else {
                        unreachable!();
                    };
                    let val_type = kv_tys[1].clone();
                    // Extract JSON value of string type to create bloom index,
                    // other types of JSON value will be ignored.
                    if val_type.remove_nullable() == DataType::Variant {
                        let mut builder = ColumnBuilder::with_capacity(
                            &DataType::Nullable(Box::new(DataType::String)),
                            column.len(),
                        );
                        for val in column.iter() {
                            if let ScalarRef::Variant(v) = val {
                                let raw_jsonb = RawJsonb::new(v);
                                if let Ok(Some(str_val)) = raw_jsonb.as_str() {
                                    builder.push(ScalarRef::String(&str_val));
                                    continue;
                                }
                            }
                            builder.push_default();

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