clockworklabs/SpacetimeDB · error

table schema should validate for query builder codegen

Error message

table schema should validate for query builder codegen

What it means

Panic in SpacetimeDB's Unreal C++ query-builder code generation. For every table in the module, the generator constructs `TableSchema::from_module_def(module, table, (), 0)` and calls `.validated()`; if the table schema collects validation errors, the `expect` panics and codegen aborts. The invariant assumed is that any table that passed module building must also pass table-schema validation.

Source

Thrown at crates/codegen/src/unrealcpp.rs:3257

            if !(constraints.has_indexed() || constraints.has_unique() || constraints.has_primary_key()) {
                continue;
            }
            let col_idx = columns.iter().next().expect("singleton column").idx();
            let (field_name, _) = &product_type.elements[col_idx];
            singleton_indexed_fields.push(field_name.deref().to_case(Case::Pascal));
        }
        singleton_indexed_fields
    };

    for table in iter_tables(module, visibility) {
        let product_type = module.typespace_for_generate()[table.product_type_ref]
            .as_product()
            .expect("query builder source should be a product type");
        let row_struct = format!("F{}Type", type_ref_name(module_prefix, module, table.product_type_ref));
        let source_pascal = table.accessor_name.deref().to_case(Case::Pascal);
        let schema = TableSchema::from_module_def(module, table, (), 0.into())
            .validated()
            .expect("table schema should validate for query builder codegen");

        let singleton_indexed_fields = singleton_indexed_fields_for_schema(&schema, product_type);

        let fields = product_type
            .elements
            .iter()
            .map(|(field_name, field_ty)| {
                (
                    field_name.deref().to_string(),
                    field_name.deref().to_case(Case::Pascal),
                    cpp_ty_fmt_with_module(module_prefix, module, field_ty, module_name).to_string(),
                    field_ty.clone(),
                )
            })
            .collect::<Vec<_>>();

        source_metas.push(QueryBuilderSourceMeta {
            row_struct,

View on GitHub (pinned to 6dee26c6ef)

Solutions

1. Build/validate the module first and read the real validation errors (`spacetime build`) instead of relying on the codegen panic message.
2. Bisect your module: comment out recently added tables and re-run codegen until the failing table is identified, then fix its definition.
3. Align versions: upgrade the `spacetime` CLI and the module's `spacetimedb-std` dependency to the same release.
4. Report upstream if a table that builds cleanly still panics here — that is a codegen invariant break, not a user error.

Example fix

// before: table whose schema fails validation (e.g. indexed unique on unsupported type)
table Player { name: String #[primary_key], payload: Bytes #[index] }

// after: index a supported, comparable type
table Player { name: String #[primary_key], score: u64 #[index] }

for table in iter_tables(module, visibility) {
    let schema = TableSchema::from_module_def(module, table, (), 0.into());
    if !schema.validated() { /* surface errors, skip codegen */ }
}

When it happens

Trigger: Running `spacetime generate` for Unreal C++ bindings where a table definition fails `TableSchema` validation: invalid index/constraint definitions, unsupported column types, or a table auto-injected with a generated row type that the validator rejects. `iter_tables(module, visibility)` feeds each table, so any single bad table kills the whole run.

Common situations: Version skew between the module SDK used to build the module and the CLI generating bindings; introducing a table with a newly supported type that older codegen validators reject; corrupted or hand-modified module description files; constraint/index syntax that changed between releases.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• Failed to generate table due to validation errors
• view schema should validate for query builder codegen
• table should exist in the database for AddConstraint
• expected ModuleDef to contain key, but it does not
• `table_id` must not be `TableId::SENTINEL` in `{row_level_se

AI-assisted analysis of clockworklabs/SpacetimeDB@6dee26c6ef (2026-08-20). Data as JSON: /api/errors/6874ce49c8c95ded. Report an issue: GitHub.